Experiment _ 1 Title _ Enthalpy of formation of calcium carbonate

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					Experiment :     1

Title :          Enthalpy of formation of calcium carbonate

Objective :      To determine the enthalpy of formation of calcium carbonate

Introduction :   The enthalpies of reaction between calcium and hydrochloric acid calcium carbonate and hydrochloric acid are
                 determined experimentally. By mean of an energy cycle, the enthalpy of formation of calcium carbonate can then be
                 calculated. The following data will be needed :

                 H2(g) + ½O2(g) → H2O(l)    ∆Hf[H2O(l)] = -286 kJmol-1
                 C(s) + O2(g) → CO2(g)      ∆Hf[CO2(g)] = -393 kJmol-1

Chemicals :      powdered calcium carbonate, 2M hydrochloric acid, calcium metal

Apparatus :      Thermometer, polystyrene cup

Procedure :      A. Reaction of calcium carbonate with dilute hydrochloric acid

                 1.   Weigh out accurately about 2 g of dry powdered calcium carbonate directly into a clean dry plastic cup.
                 2.   Place about 50 cm3 of the hydrochloric acid in a measuring cylinder. Record its temperature every half minute.
                      At exactly the second minute, pour the acid on the carbonate in the plastic cup.
                 3.   Stir gently with the thermometer and record the temperature every half minute until the seventh minute.
                 4.   Tabulate your results.
                 5.   Plot the graph of temperature of the liquid against time.
                 6.   Calculate the molar heat of reaction between calcium carbonate and dilute hydrochloric acid.

                 B. Reaction of calcium with dilute hydrochloric acid

                 1.   Weigh out accurately about 0.5 g of calcium metal.
                 2.   Using a measuring cylinder, place 50 cm3 of the hydrochloric acid in a plastic cup. Stirring carefully with the
                      thermometer provided, measure the temperature of the acid every half minute. Tabulate your results.
                 3.   At exactly the second minute add the metal to the acid and continue taking the temperature of the liquid every
                      half minute until the seventh minute, stir the liquid throughout.
                 4.   Plot the graph of temperature of the liquid against time.
                 5.   Calculate the molar heat of reaction between calcium and dilute hydrochloric acid.

                 C. Determination of enthalpy of formation of calcium carbonate
                    With the data provided and the results from part A and B, use Hess's law to calculate the enthalpy of formation
                    of calcium carbonate.
                    Hints : 1. What is the equation for the formation of calcium carbonate from its elements under standard
                                 conditions? [equation 1]
                             2. Write an ionic equation for the reaction that has taken place in A [ equation 2 ]
                             3. Write an ionic equation for the reaction which has taken place in B. [equation 3 ]
                             4. Draw an energy cycle linking equation 1, 2 and 3 together.

Results :        Specific heat capacity of water = 4.17 Jg-1K-1
                 Density of water = 1.00 gcm-3

Questions :      1.   What does the term standard enthalpy of formation mean?
                 2.   What are the “standard conditions” of thermochemistry?
                 3.   Why is the exact concentration of the hydrochloric acid unimportant?
                 4.   In this experiment, did we assume that there was no heat lost to the surrounding ?
                 5.   What other assumption(s) has you made in this experiment ?
Experiment :     2

Title :          Preparation of standard solution and standardization of hydrochloric acid

Objective :      To prepare a standard solution of sodium carbonate and use it to standardize a given solution of dilute hydrochloric
                 acid.

Introduction :   Anhydrous sodium carbonate is a suitable chemical for preparing a standard solution (as a primary standard). The
                 molarity of the given hydrochloric acid can be found by titrating it against the standard sodium carbonate solution
                 prepared.
                 The equation for the complete neutralization of sodium carbonate with dilute hydrochloric acid is
                                                 Na2CO3(aq) + 2HCl(aq) → 2NaCl(aq) + CO2(g) + H2O(l)

                 The end-point is marked by using methyl orange as indicator.

Chemicals :      solid sodium carbonate, 0.1 M hydrochloric acid

Apparatus :

Procedure :      1.   Weight out about 1.3 g of anhydrous sodium carbonate accurately using the method of “weighing by
                      difference”.
                 2.   Transfer the weighed carbonate to a beaker and add about 100 cm3 of distilled water to dissolve it completely.
                 3.   After dissolving, transfer the solution to a 250.0 cm3 volumetric flask. Rinse the beaker thoroughly and transfer
                      all the washes into the volumetric flask. Remember not to overshoot the graduation mark of the flask.
                 4.   Make up the solution to the mark on the neck by adding water.
                 5.   Pipette 25.0 cm3 of sodium carbonate solution to a clean conical flask.
                 6.   Add 2 drops of methyl orange indicator to the carbonate solution.
                 7.   Titrate the carbonate solution with the given dilute hydrochloric acid until the colour of solution just changes
                      from yellow to orange.
                 8.   Repeat the titration two times (you may repeat until all your reagents are used up).

Calculation :    Calculate the molarity of the sodium carbonate solution prepared and the molarity of the hydrochloric acid.

Results :        Weighing
                 Mass of weighing bottle + solid     = _______________ g
                 Mass of emptied weighing bottle = _______________ g
                 Mass of solid (              ) used = _______________ g

                 Titration
                 Burette contained               :
                 Conical flask contained         :
                 Indicator used                  :

                 Burette Readings:
                 Volume in cm3                             Trial                  1                     2
                 Final Burette reading
                 Initial Burette Reading
                 Volume of titrant used

                 Average titre used = _______________ cm3

                 Other Observations :

Questions :      1    What is the meaning of “weighing by difference”?
                 2.   Suggest one method other than using acid-base indicator to detect the end point of an acid-alkali titration.
Experiment :     3

Title :          Redox titration – ethane-1,2-dioic acid vs potassium permanganate

Objective :      To prepare a standard solution of ethane-1,2-dioic acid (oxalic acid) and use it to standardize a solution of
                 potassium permanganate.

Introduction :       Permanganate ion, MnO4-(aq), is a strong oxidant. Since permanganate ion is intensely coloured and its
                 reduction product, Mn2+(aq), is almost colourless, a self-indicating titration is possible. The addition of the first drop
                 of permanganate solution in excess imparts a pink colour to the solution.

                 In strongly acidic medium, permanganate undergoes a 5 electrons reduction to manganese(II) ion:
                                                  MnO4-(aq) + 8H+(aq) + 5e- → Mn2+(aq) + 4H2O(aq)

                 Ethane-1,2-dioate (oxalate) ions are oxidized according to
                                                                  O O
                                                             -O   C   C O-   (aq)   → 2CO2(g) + 2e-

                      Potassium permanganate does not oxides oxalates in cold solution. A temperature of about 70ºC is necessary
                 to cause the reaction to occur rapidly.

                      Formula mass of ethane-1,2-dioic acid (H2C2O4·2H2O) is 126. A 0.05 M solution of ethane-1,2-dioic acid is to
                 be prepared by weighing out about 1.5 g of the acid and made up to 250.0 cm3 of solution on a standard volumetric
                 flask.

Chemicals :      3M H2SO4(aq), 0.02M KMnO4(aq), H2C2O4·2H2O(s)

Apparatus :

Procedure :      [Hazard Warning: oxalate is poisonous.]

                 1.   Weigh out accurately about 1.5 g ethane-1,2-dioic acid, dissolve in water and make up to 250.0 cm3.
                 2.   Pipette 25.0 cm3, using a pipette filler, of the prepared solution into a conical flask. Add about 25 cm3 of 3 M
                      H2SO4 and heat the mixture on a tripod to about 60ºC (The temperature can be estimated by using your fingers.
                      Swirl the flask for a about 10 seconds, if the side of the flask is still just too hot to be touched, the temperature
                      of the liquid is approximately correct.)
                 3.   Titrate with the potassium permanganate solution till a permanent pink coloration is observed. Heat the solution
                      occasionally to maintain the temperature at 60ºC. Swirl the flask continuously throughout titration.
                 4.   Repeat the titration for two times.

Calculation :    Calculate the concentration of the potassium permanganate solution in molarity and in gdm-3.

Results :

Questions :      1.   Why is it that potassium permanganate is used as a titrant in acidic solution?
                 2.   In the above titration, what conditions should be maintained?
                 3.   Close observation of the solution during the titration may reveal the evolution of small gas bubbles. What gas
                      or gases are formed?
                 4.   Dichromate ion is also a strong oxidant. Do you think that dichromate titrations could also be self-indicating?
                      Half-reaction of dichromate is:
                      Cr2O72-(aq) + 14H+(aq) + 6e- → 2Cr3+(aq) + 7H2O(l)
                      orange                          green
Experiment :     4

Title :          Analysis of Two commercial Brands of Bleaching Solution

Introduction :        Sodium chlorate(I) (sodium hypochlorite) forms the basis of most commercial bleaches. The amount of this
                 active ingredient available can be estimated by the following method.
                      In this analysis, the sodium chlorate(I) is allowed to react with an excess of potassium iodide solution in the
                 presence of acid, liberating iodine, which is then titrated against standard sodium thiosulphate solution. The
                 reactions involved are:

                                                   ClO-(aq) + 2I-(aq) + 2H+(aq) → I2(aq) + H2O(l) + Cl-(aq)
                                                         I2(aq) + 2S2O32-(aq) → 2I-(aq) + S4O62-(aq)

Chemicals :      Commercial bleach (2 brands), 1 M KI, dilute H2SO4, 0.0500 M Na2S2O3, starch indicator (freshly prepared)

Apparatus :      Titration apparatus, measuring cylinder

Procedure :      1.   Pipette 5.0 cm3 of the bleach into a clean 250.0 cm3 volumetric flask. Make up to the mark using deionized
                      water.
                 2.   Pipette 25.0 cm3 of this solution into a conical flask, add to it 10 cm3 of 1 M potassium iodide solution and 10
                      cm3 of dilute sulphuric(VI) acid.
                      [Hazard Warning: Bench dilute sulphuric(VI) acid is corrosive.]
                 3.   Titrate this against the 0.050 M sodium thiosulphate solution. Add about 1 cm3 drops of freshly prepared starch
                      indicator when the reaction mixture turns pale yellow and continue to titrate to the end-point. Repeat your
                      titration twice.
                 4.   Repeat steps (1) to (3) with another brand of bleach.

Calculation :    For each brand, work out
                 (a) the amount of the active ingredient available in gdm-3.
                 (b) the cost per gram of this compound.

Results :        Concentration of standard sodium thiosulphate solution provided : __________ M

                 Brand A
                 Trade Name: _______________ Manufacturer: _______________ Price: __________ Volume : __________

                 Brand B
                 Trade Name: _______________ Manufacturer: _______________ Price: __________ Volume : __________

Questions :      1.   According to your results, which of the two brands of bleach is a better buy?
                 2.   Why should potassium iodide be present in excess?
                 3.   What is the function of the dilute sulphuric(VI) acid ?
                 4.   With reference to the experimental procedure, potassium iodide solution should be added to the bleaching
                      solution before the dilute sulphuric acid(VI) is added. What would happen if dilute sulphuric acid(VI) is added
                      first instead ?
                 5.   The starch indicator should not be added too early. Why?
                 6.   What is the difference between deionized water, distilled water and tap water ?
Experiment :     5

Title :          Organic qualitative analysis (Sodium fusion test)

Objective :      To test for the presence of nitrogen, sulphur and halogen in an organic compound.

Introduction :

Chemicals :      small sodium granules, FeSO4(s), 1.0 M H2SO4(aq), FeCl3(aq), sodium nitroprusside, lead(II) acetate, 0.1 M AgNO3(aq),
                 ethanoic acid, 2.0 M HNO3(aq)
Apparatus :

Procedure :      [Hazard Warning: Wear Safety Goggles]

                 The Sodium Fusion Test (Lassaigne Test) – Detection of nitrogen , sulphur and halogens.

                 1.   Put 2 – 3 drops of the unknown substance (if liquid) or about 0.1 g (if solid) in a small combustion / ignition
                      tube.
                 2.   Place a small piece of freshly cut sodium (about 3 mm cube) half way down the tube.
                 3.   Hold the tube with a pair of tongs. Start the heating gently to avoid spurting out of the sodium. When the
                      sodium is molten, heat the compound strongly until the end of the tube is red hot.
                 4.   The tube, while still hot, is plunged into about 20 cm3 cold distilled water in a beaker.
                 5.   The mixture is boiled gently until it is concentrated to about 10 cm3, stirred with a glass rod and then filtered.
                      The filtrate which should be both clear and colourless, is readily to be examined for the presence of nitrogen,
                      sulphur and halogens.

                 Test for Nitrogen (Cyanide Test) –          The Lassaigne test converts any nitrogen present in the compound to
                                                             sodium cyanide.
                 a.   To 1 cm3 of filtrate, add a few drops of freshly prepared solution of solid iron(II) sulphate and a dark green
                      precipitate of iron(II) hydroxide is formed.
                 b.   If sulphur is also present, precipitate will be black, rather more iron(II) sulphate solution should be added.
                 c.   The mixture is heated to boiling with shaking, cooled and acidified with dilute sulphuric acid. If nitrogen is
                      present, a blue colour (prussian blue) appears immediately on addition of a trace of iron(III) chloride solution.
                      (N.B. If the proportion of nitrogen is low, only a greenish suspension may result, but when this is filtered and
                      the paper washed, any blue precipitate present is usually visible.)

                 Test for sulphur (Sulphur test) – The Lassaigne test converts any sulphur present in the compound to sodium
                                                      sulphide.
                 a. To 1 cm3 of the filtrate, add a few drops of cold, freshly prepared, dilute solution of sodium
                     pentacyanonitrosylferrate(II) (nitroprusside). If sulphide ion (hence sulphur) is present, a deep purple colour
                     will appear.
                 b. Alternatively, sulphide ion (hence sulphur) may be detected by precipitation as black lead(II) sulphide with
                     lead(II) acetate solution which has been acidified by acetic acid.

                 Test for halogens – The Lassaigne test converts any halogens present in the compound to sodium halides.
                 a. Acidify 1 cm3 of the filtrate with a few drops of 2.0 M dil. nitric acid.
                 b. Silver nitrate solution is then added to the solution. Halides (hence halogens) are indicated by the formation of
                     a white or yellow precipitate.
                     (N B. If nitrogen and / or sulphur have been detected, the acidified solution must be boiled for a couple of
                     minutes to expel hydrogen cyanide (BE VERY CAREFUL! Do this part in the fume cupboard if the
                     amount is large!) and hydrogen sulphide which interfere with the test, before adding the silver nitrate
                     solution.)

Results :        Describe what happened during the preparation of the fusion solution. For each test, write down the observations,
                 and deduce the elements present in the unknown.

Questions :
Experiment :     6

Title :          Estimation of strength of hydrogen bond

Introduction :        Breaking or formation of intermolecular hydrogen bonds between molecules in liquids would cause an enthalpy
                 change when the liquids are mixed. This experiment is to investigate such enthalpy changes and to measure
                 approximate strengths of hydrogen bonds formed between molecules of ethanol and those between molecules of
                 trichloromethane and ethyl ethanoate using simple calorimetric methods.

Chemicals :      Ethanol, cyclohexane, ethyl ethanoate, trichloromethane

Apparatus :      10 cm3 and 25 cm3 measuring cylinders, 50 cm3 beaker, 250 cm3 beaker, -10 – 110 °C thermometer, cotton wool

Procedure :      [Hazard Warning: Ethanol, cyclohexane and ethyl ethanoate are flammable, trichloromethane is harmful, and
                 tetrachloromethane is toxic.]

                 A. To measure the strength of hydrogen bond formed between ethanol molecules

                      1.   Using a measuring cylinder, add 5 cm3 of ethanol into an insulated 50 cm3 beaker. Measure the
                           temperature of the liquid.
                      2.   Then add 20 cm3 of cyclohexane to the ethanol in the beaker, mix well and record the lowest temperature
                           attained.
                      3.   From the temperature drop estimate the hydrogen bond strength (in kJmol-1) in ethanol.

                 B. To measure the strength of hydrogen bonds formed between molecules of ethyl ethanoate and
                    trichloromethane

                      [Hazard Warning: Mixtures of trichloromethane and propanone have been known to explode on standing. The
                      solvent residues from this experiment should not be disposed of into a container in which propanone is
                      present.]

                      1.  Measure 5 cm3 of ethyl ethanoate into an insulated 50cm3 beaker. Record its temperature.
                      2.  Add to this 20 cm3 of trichloromethane and mix well. Record the highest temperature attained.
                      3.  From the temperature change estimate the strength of the hydrogen bond formed between molecules of
                          ethyl ethanoate and trichloromethane.
                      N.B.    Actually either ethyl ethanoate or trichloromethane can be in excess.

                 The following physical data may be useful:

                 Specific heat capacity of glass = 0.78 kJ kg-1K-1

                 Liquid                       Formula                   Relative          Density          Specific heat capacity
                                                                     molecular mass       / kgdm-3               / kJkg-1K
                 Ethanol                   CH3CH2OH                       46                0.81                    2.44
                 Cyclohexane                  C6H12                       84                0.78                    1.83
                 Trichloromethane             CHCl3                      119.5              1.48                    0.98
                 Ethyl ethanoate          CH3CO2CH2CH3                    88                0.90                    1.92

Questions :      A.   To measure the strength of hydrogen bond formed between ethanol molecules
                 1.   Why should the beaker be insulated?
                 2.   Is the mixing process endothermic or exothermic?
                 3.   Account for the temperature change.
                 4.   Explain why cyclohexane has to be used in excess in this experiment.

                 B. To measure the strength of hydrogen bonds formed between molecules of ethyl ethanoate and
                    trichloromethane
                 1. Is the mixing process exothermic or endothermic?
                 2. Account for the temperature change.
                 3. Explain why it does not matter which liquid is used in excess.
Experiment :     7

Title :          Investigation of the Order of the Reaction of Iodine with Propanone (Titration Method)

Introduction :   This is a group exercise. Students have to share their data to determine the result. The class will be divided into five
                 groups (A to E) to determine the rate of reaction between iodine with propanone at different concentrations.

Chemicals :      0.01 M Na2S2O3, 1 M H2SO4, 0.02 M I2 in KI solution (5 g I2 and 33 g KI in 1 dm3 solution), 1 M aqueous
                 propanone, 0.5 M NaHCO3, 0.1 M NaHSO3, starch solution

Apparatus :      Titration apparatus, 10.0 cm3 pipette, beakers, stop watch, 100 cm3 measuring cylinder

Procedure :      1.   Pipette 25.0 cm3 of 1 M sulphuric(VI) acid, and deliver from burettes, V1 cm3 of 1 M propanone solution and
                      V2 cm3 of distilled water into a conical flask as follows:
                      [Hazard Warning: 1 M sulphuric(VI) acid is corrosive, and propanone is flammable.]
                      (Note: Each group should prepare one of the combinations of solutions indicated below.)

                      Group                            A       B        C      D      E
                      Volume of propanone             25.0    20.0     15.0   10.0   5.0
                      solution (V1 / cm3)
                      Volume of deionized water        0.0       5.0   10.0   15.0   20.0
                      (V2 / cm3)

                 2.   Run 50.0 cm3 of the 0.02 M iodine solution from a burette into a beaker. Transfer this iodine solution to the
                      propanone mixture as quickly as possible and at the same time start the stop watch. Mix the contents.
                 4.   After 5 minutes, pipette 10.0 cm3 of the reaction mixture into a clean conical flask. Add 10 cm3 of the 0.5 M
                      sodium hydrogencarbonate solution to the conical flask. Note the time of addition of sodium
                      hydrogencarbonate. Mix the solution thoroughly and then titrate with the diluted sodium thiosulphate solution
                      using starch as indicator.
                 5.   After 10, 15, 20, 25 and 30 minutes, withdraw 10.0 cm3 portions of the reaction mixture from the flask and
                      carry out step (4) for each portion
                 6.   Record your results in the following table.

                      Time when NaHCO3 was added /
                      sec
                      Final burette reading / cm3
                      Initial burette reading / cm3
                      Volume of Na2S2O3 used / cm3

Calculation :    1.   Plot a graph of the volume of sodium thiosulphate needed to react with the remaining iodine against the time
                      at which the 10.0 cm3 sample of the reaction mixture was added to the sodium hydrogencarbonate solution.
                 2.   Find the gradient of the graph.
                 3.   Record the gradients of the graphs obtained by the five groups:

                      Group                                  A         B       C        D         E
                      Gradient of graphs / cm3sec-1

                 4.   Plot the gradients of graphs against the initial volumes of propanone solution added. Deduce from the graph the
                      relationship between the rate of the reaction and the concentration of propanone. Hence determine the order of
                      the reaction with respect to propanone.

Questions :      1.   Acid is used as a catalyst for the reaction between propanone and iodine. What is the purpose of adding sodium
                      hydrogencarbonate in step (4)?
                 2.   How does the concentration of iodine change throughout the experiment?
                 3.   Does the rate of the reaction, which in this case is directly proportional to the gradient of the graph, vary with
                      different concentrations of iodine?
                 4.   What is the order of the reaction with respect to iodine?
                 5.   Give the rate equation for this reaction.
Experiment :     8

Title :          To Determine the Activation Energy of the Reaction between Bromide Ion and Bromate(V) Ion in Acid Solution

Introduction :        During a reaction, bonds are first broken, and others are then formed. Energy is required to break certain bonds
                 and start this process, no matter the overall reaction is exothermic or endothermic. Particles will not always react
                 when they collide because they may not possess sufficient energy for the appropriate bonds to break.
                 A reaction will only occur if the colliding particles possess more than a certain minimum amount of energy known
                 as the activation energy, EA.

                     Using the kinetic theory and probability theory, Maxwell and Boltzmann showed that the fraction of molecules
                 with energy greater than EA Jmol-1 was given by e-EA/RT where R is the gas constant, T is the absolute temperature
                 and e is the exponential function.

                    This suggest that at a given temperature: Reaction rate α e-EA/RT. But as k, the rate constant for a reaction, is a
                 measure of the reaction rate, we can write

                          k α e-EA/RT
                          k = A e-EA/RT

                     This last expression is called the Arrhenius equation.

                     In acidic solution, the reaction between bromide ion and bromate(V) ion can be represented by

                                                     5Br-(aq) + BrO3-(aq) + 6H+(aq) → 3Br2(aq) + 3H2O(l)

                      The progress of the reaction may be followed by adding a fixed amount of phenol together with some methyl
                 red indicator. The bromine produced during the reaction reacts very rapidly with phenol (forming tribromophenol).
                 Once all the phenol is consumed, any further bromine bleaches the indicator immediately. So, the time for the
                 reaction to proceed to a given point may be determined.

                                                   concentration change time
                     Now, as k α reaction rate =
                                                              time


                     As for the concentration change in this experiment is constant,

                                                      1
                              kα
                                     time for methyl red to be bleached

                                     constant
                              k=
                                        t

                                  constant
                              ln (          ) = ln A + ln e-EA/RT
                                       t
                                                  1           EA
                              ln (constant) + ln = ln A -
                                                  t           RT
                                                              EA
                              ln t = [ln A - ln (constant)] -
                                                              RT

                                                 1        1                    EA
                              so a graph of ln     against has a gradient of -    .
                                                 t        T                    R


Chemicals :      50 cm3 solution A (0.083 M with respect to KBr and 0.017 M with respect to KBrO3), 25 cm3 0.5 M H2SO4, 50 cm3
                 0.01 M phenol solution, methyl red indicator

Apparatus :      Beaker, boiling tube, stop watch, two -10 – 110 °C thermometers, burette
Procedure :     [Hazard Warning: 0.5 M sulphuric(VI) acid is irritant, and phenol is toxic.]

                1.   Place 10.0 cm3 of 0.01 M phenol solution, 10.0 cm3 solution A and 2 drops of methyl red indicator into a
                     boiling tube.
                2.   Place 5.0 cm3 of 0.5 M sulphuric(VI) acid into a second boiling tube.
                3.   Place both boiling tubes into a beaker of water which is maintained at about 30°C. Allow the contents of the
                     tubes to reach the temperature of the water bath.
                4.   Pour the content of the first boiling tube into the sulphuric(IV) acid, and at the same time start the stop watch.
                     Swirl well for 5 seconds.
                5.   Keep the second boiling tube in the water bath throughout the experiment. Record the time (t) taken when the
                     red colour fade.
                6.   Record also the temperature (T), to the nearest degree, of the reaction mixture at the end of the experiment.
                7.   Repeat steps (1) to (6), maintaining the reaction temperature at about 35 °C, 40 °C, 45 °C and 50 °C.

Calculation :   Determine Ea by plotting a suitable graph. (Given: R = 8.314 J K-1mol-1)

Result :
                                                                                        Temperature
                      Experiment          Time t / s               1              T / ºC            T/K               1/T / K-1
                                                                ln
                                                                   t
                            1
                            2
                            3
                            4
                            5

Questions :     1.   Give an equation for the reaction between phenol and bromine.
                2.   What is the use of methyl red in this experiment?
                3.   Should the time be taken when the methyl red starts to fade or when the methyl red becomes colourless ? Why?
                3.   Based on your results, is it advisable to perform the experiment at high temperatures such as 80 °C?
                4.   Why is it not necessary to know how far the main reaction has proceeded at the point where the methyl red is
                     decolorized ?
                5.   The Arrhenius equation can be represented as:
                         k = A e-EA/RT
                     (a) Can 1/t substitute k in this equation? Why?
                     (b) Derive an equation relating ln k and 1/T.
                6.   Explain why the reaction rate can be affected by temperature.
Experiment :     9

Title :          Hydrolysing organic halogeno-compounds

Objective :      The purpose of this experiment is to find out how the rate of hydrolysis of an organic halogen compound depends
                 on:
                 (a) the identity of the halogen atom,
                 (b) the nature of the carbon-hydrogen 'Skeleton'.

Introduction :   In this experiment, you compare the rates of hydrolysis of 1-chlorobutane, 1-bromobutane, 1-iodobutane and
                 chlorobenzene. A general equation for the hydrolysis is:

                          R–X + H2O    → R–OH + H+ + X-                  (where R = alkyl or aryl group; X = halogen atom).

                 You can follow the rate of the reaction by carrying it out in the presence of silver ions, so that any halide ions
                 produced form a silver halide precipitate.

                          Ag+(aq) + X-(aq)   → AgX(s)

                 Since halogenoalkanes and halogenoarenes are insoluble in water, ethanol is added to act as a common solvent for
                 the halogeno-compounds and silver ions.

Chemicals :      Ethanol, 1-chlorobutane, 1-bromobutane, 1-iodobutane, chlorobenzene, 0.05 M silver nitrate solution

Apparatus :      Stop-clock, 0–100 ºC thermometer,

Procedure :      1.   Set up the apparatus shown in the figure.

                 2.   Pour 2 cm3 of ethanol into each of four test-tubes and mark them with the letters A to D.
                 3.   Add 3-4 drops of 1-chlorobutane to A, 3-4 drops of 1-bromobutane to B, 3-4 drops of 1-iodobutane to C and 3-
                      4 drops of chlorobenzene to D.
                 4.   Pour about 5 cm3 of silver nitrate solution into the fifth test-tube.
                 5.   Stand all the test-tubes in the beaker (or water-bath) and heat to 60 ºC. Remove the Bunsen burner.
                 6.   Quickly add 1 cm3 of aqueous silver nitrate to each of the tubes A to D and start the clock. Shake each tube
                      once to mix the contents, and leave in the water with the cork resting loosely on the tube to reduce evaporation.
                 7.   Watch the tubes continuously for about ten minutes and note the time when a cloudy precipitate first appears in
                      each tube. If necessary, heat the water to 60 ºC again at intervals.
                 8.   Continue observation at intervals for about 30 minutes more, noting any further changes in the appearance of
                      the precipitates.

Results :
                 Reaction                    Time for precipitate to appear                           Observations
                 A. 1-chlorobutane
                 B. 1-bromobutane
                 C. 1-iodobutane
                 D. chlorobenzene

Questions :      1. List the compounds in order of speed of hydrolysis, fastest first.
                 2. Suggest an explanation for this order in terms of the C-halogen bond energies.
                 3. . Write equations for the hydrolysis reactions which occur in this experiment.
Experiment :     10

Title :          Preparation of bromobutane

Objective :      To prepare bromobutane from butanol

Introduction :   Bromobutane (b.p. 101.6ºC) can be prepared by reacting butanol (b.p. 117.3ºC) with a mixture of potassium (or
                 sodium) bromide and concentrated sulphuric acid (b.p. 338ºC). Bromobutane can be distilled out after its
                 formation. The product prepared in this way will be impure and requires further purification. The purity of the
                 product can be checked from its refractive index.

                 Physical properties of bromobutane:
                 – colourless liquid; immiscible with water

Chemicals :      Butanol, sodium bromide, ice, anti-bumping granules, sodium carbonate solution, anhydrous calcium carbonate.

Apparatus :      Quick fit apparatus, -10 – 100 ºC thermometer,

Procedure :      A. Preparation of bromobutane (3 lessons)

                 1.   Place 5 g (weigh accurately) of powdered sodium bromide and
                      30 pieces of anti-bumping granules in a 50 cm3 pear shaped
                      flask.
                 2.   Add 10 cm3 of butanol. Cold the mixture in an ice bath.
                 3.   With constant swirling and cooling in the ice bath, add 7 cm3 of
                      concentrated sulphuric acid slowly.
                 3.   Assemble the "quick fit" apparatus as shown in figure.
                 4.   Put a little icy water into the receiving test tube. (The tip of the
                      receiver should only touch the surface of the water to avoid
                      sucking back.)
                 5.   Heat the flask very gently (temperature should be kept at
                      around 85°C) over a gauze, taking care to avoid excessive
                      frothing. Continue heating until no more oily drops of
                      bromobutane distil over / all the sodium bromide disappear.
                      The bromobutane is collected in the test tube surrounded by
                      cold water.

                 B. Purification of bromobutane (This step will be done by the teacher) (2 lessons)

                 Transfer all your crude product in your test tube to your teacher's flask.

                 The distillate contains sulphurous and hydrobromic acid as impurities and may be purified as described.

                 Transfer the distillate to the separating funnel. Remove the lower oily layer, discard the aqueous layer, and return
                 the oil to the separating funnel. Add about 3 cm3 of dilute sodium carbonate solution, fit the stopper and shake.
                 Remove the stopper occasionally to relieve the pressure. Allow the mixture to settle, and discard the upper aqueous
                 layer. Wash the impure bromobutane with water, discard the upper layer, and dry it over anhydrous calcium
                 chloride in a stoppered test-tube. Redistil the bromobutane, collecting the fraction boiling at about 100ºC. Obtain
                 the refractive index of bromobutane produced by using a refractometer.

                 Density of butanol : 0.8098 gcm-3 boiling point : 117.3ºC
                 Density of bromobutane : 1.2758 gcm-3 boiling point : 101.6ºC

Results :        Give details on what did you observe during the course of experiment and calculate the yield of the preparation.

Questions :      1.   Which is the limiting reagent in the preparation of bromobutane ?
                 2.   Comment on the yield of product.
                 3.   Suggest 3 functions of concentrated sulphuric acid in this experiment.
                 4.   Suggest what impurities are present in crude bromobutane. Then explain why sodium carbonate is used in the
                      purification of bromobutane.
                 5.   Why it is necessary to release the pressure inside the separating funnel regularly?
                 6.   Can iodobutane be prepared by this method? Explain?
Experiment :     11

Title :          Separation of Amino Acids by Paper Chromatography

Introduction :   A mixture of unknown amino acids can be separated and identified by means of paper chromatography. The
                 positions of the amino acids in the chromatogram can be detected by spraying with ninhydrin, which reacts with α-
                 amino acids to yield highly coloured products.

Chemicals :      2% ammonia, propan-2-ol, aluminium foil, ninhydrin spray (2% solution of ninhydrin in ethanol), separate solutions
                 of 0.05 M glycine, tyrosine, leucine, and aspartic acid in 1.5 % HCl in 4 test tubes, an unknown containing one to
                 four of the above amino acids at a concentration of about 0.05 M each in 1.5 % HCl

Apparatus :      Capillary tube, Whatman chromatography paper, beaker, oven

Procedure :      1.   Mix 10 cm3 of 2 % ammonia solution with 20 cm3 of propan-2-ol in a clean, 500 cm3 beaker, and cover tightly
                      with a piece of aluminium foil. This would be used as the solvent for the experiment. [Hazard Warning:
                      Propan-2-ol is flammable.]
                 2.   On a clean sheet of chromatography paper with size about 12 cm by 22 cm, mark a light pencil line parallel to
                      the bottom and about 1.5 cm away (Figure 1). Along this line mark ten light crosses ("×") at intervals of about 2
                      cm. Label each cross as shown in Figure 1. ("U" represents the unknown amino acid mixture.)




                 3.   Using capillary tubes, place a small amount of each appropriate solution on its two positions along the line on
                      the chromatography paper. Avoid getting the spot on the paper larger than about 2 mm in diameter. Let the
                      paper dry for a few minutes in air. Add a second portion of the unknown to one of its two positions, to make
                      certain that sufficient quantities of each component of the unknown will be present for good visual observation
                      when the paper is developed.
                 4.   Roll the paper into a cylindrical form. Staple the ends together in such a fashion that they do not touch each
                      other (Figure 2). Otherwise the solvent will flow more rapidly at that point and form an uneven solvent front.
                 5.   When the spots on the cylindrical paper are dry (it may be necessary to place the paper in an oven at about
                      100°C for a short time), place it carefully in the beaker of solvent, and cover carefully and tightly with the
                      aluminium foil. Make sure that the paper does not touch the wall of the beaker.
                      Let the solvent rise up the paper for at least 1.5 hours. If the time is shorter, the components may not be
                      sufficiently separated for easy identification. Remove the paper and place it upside down on the desk top to dry.
                      When most of the solvent has evaporated, open the cylinder by tearing it apart where it was stapled and hang it
                      in a fume cupboard. Spray the paper lightly but completely with a solution of ninhydrin, and leave the paper in
                      the fume cupboard until the spray solution is dry.
                      [Hazard Warning: The ninhydrin solution should be kept off the body because it reacts with proteins in the skin
                      to form a rather long-lasting purple discoloration. The teacher should ensure that students wear laboratory
                      gowns, gloves and safety spectacles in carrying the experiment.]
                      Place the paper in an oven at 100°–110°C for about 10 minutes, or until all the spots have developed.
                 8.   Circle each spot with a pencil, and measure the distance each spot traveled (use the centre of the spot for
                      measurement). Measure the distance the solvent traveled at each position, and calculate the Rf values for each
                      amino acid. Determine the composition of the unknown by visual comparison of spot colours and by comparing
                      the Rf values.

                                                                   distance travelled by the colour spot
                                                     Rf value =
                                                                  distance travelled by the solvent front
Questions :
Experiment :     12

Title :          Investigation of Some of the Properties of a Pair of Cis-Trans Isomers

Introduction :
                  HOOC                 COOH                  HOOC               H
                               C   C                                    C   C
                           H           H                            H           COOH
                           Maleic acid                             Fumaric acid
                 Maleic acid and fumaric acid are geometrical isomers of butenedioic acid.
                      Each of these isomers has its own distinctive properties such as melting point, solubility, density and stability.
                      In this experiment some maleic acid is converted to fumaric acid by heating an aqueous solution of maleic acid
                 in the presence of hydrochloric acid. The hydrochloric acid serves merely as a catalyst of the reaction. The
                 properties of these two isomers are then compared.

Chemicals :      Maleic acid, magnesium ribbon, Na2CO3, concentrated HCl, bromine water, pH paper

Apparatus :      100 cm3 and 250 cm3 beakers, watch glass, apparatus for suction filtration, melting point apparatus, 25 cm3
                 measuring cylinder

Procedure :      [Hazard Warning: Maleic acid is irritant, concentrated hydrochloric acid is corrosive, and bromine water is
                 harmful.]

                 A. Conversion of maleic acid to fumaric acid

                      1.   Weigh out about 4 g of maleic acid in a clean dry 100 cm3 beaker. Add 10 cm3 of deionized water and
                           warm slightly to dissolve the acid.
                      2.   Add 10 cm3 of concentrated hydrochloric acid, and cover the beaker with a watch glass. Place the beaker
                           inside a 250 cm3 beaker which is about one third full of water. Heat this water bath to boiling for about 15
                           minutes or until a solid material forms in the small beaker.
                      3.   Cool the solution to room temperature by placing the small beaker with its contents in a cold water bath or
                           in an ice bath.
                      4.   Filter the reaction mixture by suction using the following set-up:




                      5.   Stop suction, either by lifting the funnel or by disconnecting the tubing, and soak the residue in about 1
                           cm3 of cold water. (If you turn off the tap, you may get a "suck-back" of water.)
                      6.   Resume suction and dry the crystals by drawing air through them for a few minutes.
                      7.   Transfer the crystals into a weighed watch glass and dry over a steam bath.
                      8.   Weigh the dried crystals of fumaric acid.

                 B. Comparison of properties of the two isomers

                      1.   Solubility in water – place about 1 g of each isomer into 10 cm3 of water in separate test tubes, shake to
                           help dissolving. See which isomer is more soluble.
                      2.   Melting point – using the electrical melting point apparatus, measure the melting points of the two isomers.
                      3.   Acid strength – for each of the two isomers, prepare a solution by dissolving about 0.1 g of the compound
                           in about 20 cm3 of distilled water. Divide the solution into 3 portions, one for each of the following tests:
                           (a) Measure the pH of the solution.
                           (b) Add a 3 cm strip of magnesium ribbon.
                           (c) Add a small amount of solid sodium carbonate.
                      4.   Reaction with bromine water—suspend about 0.1 g of the acid in about 5 cm3 of water. Add 3 drops of
                           bromine water to the resulting solution/suspension. Shake and observe.
Results :     A. Conversion of maleic acid to fumaric acid

                   Mass of fumaric acid + watch glass                 g
                   Mass of watch glass                                g
                   Mass of fumaric acid                               g
                   Percentage yield                                   %

              B. Comparison of properties of the two isomers

              1.   Water solubility: __________ acid is more soluble.
              2.   Melting point of maleic acid: __________ °C
                   Melting point of fumaric acid: __________ °C
              3.   Acid strength

                   Test                                 Maleic acid                      Fumaric acid
                   pH of solution
                   Reaction with Mg
                   Reaction with Na2CO3

              4. Reaction with bromine water
              Maleic acid:    ____________________________________________________________________________
              Fumaric acid:   ____________________________________________________________________________

Questions :   1.   Assuming that equilibrium concentration was achieved in procedure A, which isomer would you classify as the
                   more stable with respect to transformation of one into the other?
              2.   What do each of the following tests contribute to your knowledge of the structure of each isomer?
                   (a) The reaction with magnesium and sodium carbonate.
                   (b) The pH value.
                   (c) The melting point.
              3.   Considering the structures of the two isomers, try to account for the observed differences in solubility and
                   melting point.
              4.   One of the isomers can lose a molecule of water from each molecule of acid when its two carboxyl groups react
                   to form an anhydride. Which structural isomer, cis- or trans-, do you predict it is?
              5.   Is there any reaction between maleic acid and bromine water ? Suggest a reason.
Experiment :     13

Title :          Chemical properties of non-aromatic hydrocarbons

Objective :      The purpose of this experiment is to test the reactivity of the hydrocarbon using hexane as an example and compare
                 the reactivities of hexane, cyclohexane and cyclohexene.

Introduction :   You will be using hexane, cyclohexane and cyclohexene, because they are liquids which make them easy to handle,
                 and because they are cheap. You will use 5 simple test-tube reactions to compare the reactivities of the 3
                 hydrocarbons.

Chemicals :      Hexane, cyclohexane, cyclohexene, bromine dissolved in 1,1,1-trichloroethane, concentrated ammonia solution,
                 bromine water, 0.01 M potassium manganate(VII) solution, concentrated sulphuric acid.

Apparatus :      Teat pipettes, watch-glass, wood splints, aluminium foil, test tubes stoppers, lamp with 100 watt bulb

Procedure :      [Hazard Warning: Bromine is dangerously toxic and corrosive, especially in its liquid state. Solutions, such as
                 those used in this experiment, must also be treated with care. Do the experiment in a fume cupboard, keep the top
                 on the bottle as much as possible. Cyclohexane is very flammable keep the top on the bottle as much as possible.
                 Keep the bottle away from flames. Wear safety spectacles. Concentrated sulphuric acid is very corrosive and reacts
                  violently with water. Dispose of unwanted acid by cooling and pouring slowly into an excess of water.]

                 A. Combustion

                      1.    Place your watch glass on a heat resistant mat.
                      2.    Using a teat-pipette, place 10 drops of hexane on the watch-glass. (Remember : no more than 10 drops.)
                      3.    Stopper and remove the bottle of hexane to a safe place away from the watch-glass and any Bunsen flames.
                      4.    Light the hexane.
                      5..   Write down
                            (a) the colour of the flame,
                            (b) whether you can see any soot produced.

                 B. Reaction of bromine (dissolved in 1,1,1-trichloroethane)

                      1.    Using a teat pipette, place approximately 1 cm3 of hexane in two separate test-tubes.
                      2.    Stopper the hexane and remove it to a safe place away from flames.
                      3.    Using a teat pipette, place in each tube 1 cm3 of solution of bromine in 1,1,1-trichloroethane.
                      4.    Stopper the bromine bottle.
                      5.    Stopper both test tubes. Expose one of the test tube to strong light for about 3 minutes.
                      6.    Compare the appearance of the two test tubes.
                      7..   A gas is given off during this experiment. Think what gas could be given off and work out a test for the
                            gas. Note the test and its result..

                 C. Reaction of bromine water

                      1.    Using a teat-pipette, place approximately 1 cm3 of hexane in the test-tube.
                      2.    Stopper the bottle of hexane and remove it to a safe place away from the flames.
                      3.    Using a teat-pipette, place 5 drops of bromine water in the test-tube.
                      4.    Stopper the bottle of bromine water.
                      5.    Cork and shake the test-tube.
                            (a) Note the appearance of the reaction mixture.

                 D. Reaction of acidified potassium manganate(VII)

                      1.    Using a teat-pipette, place 3-4 drops of hexane in the test-tube.
                      2.    Pour into the test-tube approximately 1 cm3 of dilute sulphuric acid. Shake the mixture.
                      3.    Pour into the test-tube 5-6 drops of potassium manganate(VII) solution and shake the mixture.
                      4.    Note the appearance of the reaction mixture.

                 E. Reaction of concentrated sulphuric acid

                      1.    Pour into the test-tube approximately 1 cm3 of concentrated sulphuric acid.
                      2.    Pour into the test-tube approximately 1 cm3 of hexane.
                      3.    Note whether the substances mix or form two separate layers.

                 REPEAT THE PROCEDURES FOR CYCLOHEXANE AND CYCLOHEXENE. YOU ARE ADVISED TO
                 TRY OUT THE REACTIONS OF THE THREE CHEMICAL FOR A SINGLE TEST IN A ROW SO
                 THAT YOU CAN COMPARE THE DIFFERENCES AMONG THEM MORE EASILY.
Results :
                     Reaction                        Hexane                    Cyclohexane                   Cyclohexene
              A. Combustion               least sooty                                                 most sooty
                 Appearance of
                 flame
                 Sootiness
              B. Action of bromine
                 (in CH3CCl3)
              1. in dark
              2. in light

              Identification of gas
              Is there any gas
              evolved ?
              Suggest how to identify
              the gas and carry out the
              test.
              C. Action of bromine        turns cloudy under light      decolorizes and
                    water                                               turns cloudy under light
              D. Action of acidified                                                                  turns colourless
                    potassium
                    manganate(VII)
              E. Action of                no reaction                   no reaction                   chars
                    concentrated
                    sulphuric acid

Questions :   1.   Do you consider alkanes to be unreactive? Explain your answer.

              2.   (a) What are the products of complete combustion of the alkanes?
                   (b) Use your data book to write full thermo-chemical equations for the combustion of methane, ethane and
                       propane.
                   (c) How do your answers to part (b) relate to the uses of the alkanes?

              3.   (a) What is meant by the term 'substitution reaction'?
                   (b) Complete the following equation for the substitution reaction between equal amounts of cyclohexane and
                       bromine.




                   (c) What conditions favour the reaction shown in (b) above?
                   (d) In the presence of excess bromine, it is possible to substitute more than one hydrogen atom per molecule of
                       alkane. Write four equations showing all the possible substitution products of reaction between bromine
                       and methane, CH4, in sunlight. Name the products.
Experiment :     14

Title :          Properties of aliphatic and aromatic hydroxyl compounds

Objective :      To investigate the chemical properties of alkanol and phenol

Introduction :   Alkanol and phenol both contain the same functional group – hydroxyl group (–OH). However, their properties
                 differ significantly from each other. The following experiments aim at investigating their chemical properties.
                 (Note: Ethanol is taken as a representative for its homologous series.)

Chemicals :      absolute ethanol, pH paper, sodium metal, ethanoic acid, conc. H2SO4(l), phosphorus pentachloride, K2Cr2O7(aq),
                 I2/KI(aq), phenol, conc. HCl(aq), neutral FeCl3(aq), bromine water.

Apparatus :      wooden splint

Procedure :      [Hazard Warning: Phenol is corrosive, when using it, take care that solid phenol or a concentrated solution of it
                 does not fall on skin. Phenol would be absorbed into body through skin.]

                 A. Chemical properties of alkanol

                      1.   Solubility and pH
                           Mix 5 cm3 of water and 1 cm3 of ethanol in a test tube. Test the pH of the solution.
                           (Only a drop of solution should be used to wet the pH paper, don't drop the pH paper into the test tube.)

                      2.   Reaction with sodium
                           Add a SMALL pellet of sodium to 1 cm3 of absolute ethanol. Test for the gas evolved and find the pH of
                           the remaining solution.

                      3.   Reaction with organic acid – Esterification
                           Warm a mixture of 10 drops of ethanol and 5 drops of ethanoic acid with 5 drops of concentrated sulphuric
                           acid for a minute. Pour the contents of the test-tube into about 30 cm3 of water in a beaker, and smell the
                           content cautiously.

                      4.   Reaction with phosphorus pentachloride
                           Add a little phosphorus pentachloride to 1 cm3 ethanol. Put a glass rod soaked with aqueous ammonia
                           solution to the mouth of the test-tube.

                      5.   Oxidation
                           To 10 drops of ethanol, add 10 drops of dilute sulphuric acid and 5 drops of dilute potassium dichromate
                           solution. Warm the mixture gently and smell the product carefully.

                      6.   Iodoform test
                           To 1 cm3 of ethanol, add 1 cm3 of iodine in potassium iodide solution and then dilute sodium hydroxide
                           solution dropwise until the colour of iodine becomes light brown in colour. Shake the content and allow
                           the mixture to stand and observe any precipitate formed.

                 B. Chemical properties of phenol


                      1.   Solubility and pH
                           Add a few small crystals of phenol in 5 cm3 of water and shake vigorously. Note the characteristic smell of
                           phenol and test the pH of the solution.

                      2.   Reaction with sodium hydroxide
                           To about 5 cm3 of 2 M sodium hydroxide solution, add a few phenol crystals, and notice how much more
                           easily they dissolve in alkali than in water. Now add about 2 cm3 of concentrated hydrochloric acid. Note
                           the change.

                      3.   Reaction with sodium
                           Place a few crystals (1 cm of height) of phenol in a DRY test-tube and warm them until they are molten.
                           Add a SMALL cube of sodium quickly and watch carefully. DO NOT heat the tube continuously. Note the
                           change.
                           (The addition of sodium must be done immediately otherwise the molten phenol will solidified again.)

                      4.   Reaction with iron(III) chloride
                           To a small portion of an aqueous solution of phenol, add a few drops of neutral iron(III) chloride solution.
                           Note the colour of the mixture.
                  5.   Reaction with bromine water
                       Dissolve a two drops of phenol solution in 2 cm3 water. Shake and warm the solution. Allow to cool and
                       add bromine water dropwise and note any precipitate formed.

              N.B.     Aqueous solution of phenol is prepared by dissolving a very small amount of phenol is water.


Results :     Tabulate the results of Part A and B as the suggested format below:

              Treatment                    Expected observation          Observation                  Interpretation


Questions :
English Name : _________________________         Chinese Name : ____________________    Class : _____   Class no. : _____

Title of Experiment : __________________________________________________         Date of experiment : ____________________

Test (with brief description)       Expected Observation                       Observed Change
1. Acidity of phenol                i. Phenol solution will turn universal
                                        indicator red.
                                    ii. Ethanol solution will not change the
                                        colour of universal indicator.
2.   Solubility of phenol
     i. Addition of dil. NaOH(aq)   i. The phenol layer will dissolve.
     ii. Addition of dil. HCl(aq)   ii. The phenol layer will reform.
Experiment :     15

Title :          Reactions of aldehydes and ketones

Objective :      The purpose of this experiment is to compare some reactions of ethanal and propanone.

Introduction :   We have chosen ethanal and propanone as relatively safe examples of aldehydes and ketones to illustrate their
                 reactions in simple test-tube experiments.

                 The reactions or properties to be investigated are as follows:
                 A. Addition
                 B. Condensation (Addition - elimination)
                 C. Oxidation
                 D. Triiodomethane (iodoform) reaction

Chemicals :      Saturated sodium hydrogensulphite solution, ethanal, propanone, 2,4-dinitrophenylhydrazine solution, 0.1 M
                 potassium dichromate(VI) solution, Fehling’s solution, 1 and 2, 0.05 M silver nitrate solution, 10% I2 in KI(aq)

                 N.B.
                 1. Take 4 cm3 of 2,4-DNPH solution as stock and stopper the test tube when not in use.
                 2. Ethanal is very volatile with b.p. 21 ºC. The cap of the bottle must be replaced immediately after use.
                     Take 5 cm3 as your stock.

Apparatus :

Procedure :      A.   Addition reaction with sodium hydrogensulphite

                      1.   Pour about 2 cm3 of saturated sodium hydrogensulphite solution into a test-tube. Point the tube away from
                           you and add, drop by drop, a 0.5 cm3 of ethanal.
                      2.   Shake the tube gently and cool under a stream of cold water. Note your observations in a copy of Results
                           Table.
                      3.   Repeat steps 1 and 2 using propanone instead of ethanal.

                 B. Condensation reaction with 2,4-dinitrophenylhydrazine

                      1.   Put 1-2 drops of ethanal in a test-tube and add about 2 cm3 of 2,4-dinitrophenylhydrazine solution. Note
                           your observations.
                      2.   Repeat for propanone.

                 C. Oxidation reactions

                      (a) With acidified potassium dichromate(VI)
                          1. Into a test-tube, put 5 drops of ethanal, 2 drops of potassium dichromate(VI) solution and 10 drops of
                              dilute sulphuric acid.
                          2. Shake the tube gently and warm in a beaker of hot water. Note your observations.
                          3. Repeat for propanone.

                      (b) With Fehling's solution
                          1. Into a test-tube, put about 1 cm3 of Fehling's solution A and then add Fehling's solution B dropwise
                              until the precipitate just dissolves. If no precipitate is formed, just mix 1 cm3 of solution A with 1 cm3
                              of solution B.
                          2. Add about 5 drops of ethanal. Shake the tube gently and place in a beaker of boiling water for five to
                              ten minutes - until no further colour change occurs. Note your observations.
                          3. Repeat for propanone.
                   (c) With Tollen's reagent
                       1. Put about 1 cm3 of 0.05 M AgNO3 into a very clean test-tube and 2 cm3 of distilled water, 1 drop of
                          2M sodium hydroxide solution..
                       2. Drop by drop, add ammonia solution until all the precipitate of brown silver oxide dissolves (do not
                          try to get rid of all the little black specks of silver oxide). Remember to shake the test tube
                          continuously during adding to avoid the addition of excessive ammonia.
                       3. Add one or two drops of ethanal, shake the tube gently and place in a beaker of warm water at about
                          50ºC. Note your observations and immediately rinse out the test-tube.
                       4. Repeat with propanone.

              D. Triiodomethane reaction

                   1.   Into a test-tube, place five drops of ethanal followed by 1 cm3 of iodine solution, cork and shake.
                   2.   Add dilute sodium hydroxide solution dropwise until a light brown solution remains.
                   3.   Warm the solution gently. Note your observations.
                   4.   Repeat with propanone.

Results :
                                                       Observations

              Test                                     Ethanal                              Propanone
              A. Addition reaction with sodium
                   hydrogensulphite
              B. Condensation reaction with 2,4-
                   dinitrophenylhydrazine
              C. Oxidation reactions
                   (a) acidified dichromate(VI)
                   (b) Fehling's solution
                   (c) Tollen's reagent
              D. Triiodomethane reaction

Questions :   1.   Which tests serve to distinguish between ethanal and propanone?
              2.   Which reagent could be used as a general test for a carbonyl compound?
Experiment :     16

Title :          Identification of a Carbonyl Compound by Preparing its Derivative

Introduction :        Crystalline derivatives of many carbonyl compounds can be formed by condensation reactions with compounds
                 such as phenylhydrazine and 2,4-dinitrophenylhydrazine. These derivatives can usually be isolated in relatively pure
                 forms which have well defined melting points. Phenylhydrazine forms derivatives (phenylhydrazones) readily with
                 aromatic aldehydes, but in general 2,4-dinitrophenylhydrazine is preferred because its derivatives (2,4-
                 dinitrophenylhydrazones) have higher melting points and are less soluble. These derivatives are useful in
                 identification of carbonyl compounds.

Chemicals :      Fehling’s solutions, 0.05 M AgNO3(aq), dilute NaOH(aq), dil NH3(aq), 2,4-dinitrophenylhydrazine in methanol,
                 ethanol, methanol, carbonyl compound labelled X (different groups of students may work on different carbonyl
                 compounds), dilute H2SO4

Apparatus :      Beaker, 100 cm3 measuring cylinder, apparatus for melting point determination, apparatus for suction filtration,
                 rubber rings (cut from a rubber tubing of appropriate diameter), ice bath

Procedure :      [Hazard Warning: Methanol and the solution of 2,4-dinitrophenylhydrazine is flammable and toxic, methanol,
                 ethanol and many carbonyl compounds are flammable, and bench dilute sulphuric(VI) acid is corrosive.]

                 A. Preparation of 2,4-dinitrophenylhydrazone of compound X

                      1.   Add 10 drops of compound X to 5 cm3 of 2,4-dinitrophenylhydrazine solution in a 50 cm3 beaker. If
                           crystals are not formed, add about 1 cm3 of dilute sulphuric(VI) acid. If they are still not formed, warm the
                           mixture gently, then cool with scratching in ice water.
                      2.   Filter off the crystals by suction filtration. While still on suction, wash the crystals with 1 cm3 of methanol.
                      3.   Recrystallize the crystals from hot ethanol as follows:
                           (a) Transfer the crystals to a 100 cm3 beaker standing on a steam bath (or in a 250 cm3 beaker of hot
                                water).
                           (b) Dissolve the crystals in the minimum amount of hot ethanol.
                           (c) When the crystals have dissolved, cool the solution in an ice-water mixture until crystals reappear.
                           (d) Filter the crystals by suction. If necessary, rinse the beaker with the filtrate (not the extra solvent) to
                                complete the transfer. Finally, wash the crystals with a few drops of cold ethanol. Dry the crystals by
                                drawing air through them for a few minutes.
                      4.   Spread the crystals on a dry watch glass and leave overnight in a desiccator for drying.

                 B. Determination of the melting point of the 2,4-dinitrophenylhydrazone of compound X

                      1.   Introduce a small amount of the crystals into a melting point tube until a total length of about 0.5 cm is
                           compacted at the bottom of the tube.
                      2.   Attach the prepared melting point tube to the thermometer, as shown in Figure 1.
                      3.   Half-fill a boiling tube with paraffin oil, and position the thermometer with attached tube and the stirrer as
                           shown in Figure 2.
                      4.   Position the apparatus over a low Bunsen flame and gauze and gently heat the apparatus, stirring the
                           paraffin oil all the time by moving the stirrer up and down.
                      5.   Note the temperatures when the crystals start to melt and when the melting is completed.




                      6.   Compare the melting point of the crystals with the values given in the following table and thus identify
                           compound X.
                            Name                       Formula             Boiling point        Melting point of 2,4-
                                                                               / °C         dinitrophenylhydrazone / ºC
                   Aldehydes
                     methanal                  HCHO                             -21                     167
                     ethanal                   CH3CHO                            21              146, 164 (2 forms)
                     propanal                  CH3CH2CHO                         48                     156
                     butanal                   CH3CH2CH2CHO                      75                     123
                     2-methylpropanal          (CH3)2CHCHO                      64                      187
                     benzaldehyde              C6H5CHO                          178                     237
                   Ketones
                     propanone                 CH3COCH3                          56                     128
                     butanone                  CH3CH2COCH3                       80                     115
                     pentan-2-one              CH3CH2CH2COCH3                   102                     141
                     pentan-3-one              CH3CH2COCH2CH3                   102                     156
                     hexan-2-one               CH3CH2CH2CH2COCH3                128                     107
                     4-methylpentan-2-one      (CH3)2CHCH2COCH3                 117                      95
                     cyclohexanone                                              156                     162
                                                              O


Questions :   1.   What soluble impurities may be present in your product before recrystallization? How can they be removed in
                   the recrystallization process?
              2.   What factors should be considered in selecting a suitable solvent in the recrystallization step?
              3.   In the recrystallization procedure, why were the crystals dissolved in only the minimum amount of hot ethanol?
              4.   If the sample contains insoluble impurities such as pieces of filter paper, cork, etc., suggest how they can be
                   removed.
              5.   If the melting point of the 2,4-dinitrophenylhydrazone is 156 °C, suggest how you can confirm whether
                   compound X is propanal or pentan-3-one.
Experiment :     17

Title :          Chemical properties of carboxylic acids

Objective :      The purpose of this experiment is to see if carboxylic acids show the typical reactions both of alcohols and of
                 carbonyl compounds.

Introduction :   You will be carrying out some test-tube reactions on ethanoic acid. Ethanoic acid melts at 17ºC and therefore
                 freezes in cold weather. Because solid ethanoic acid looks like ice, it is often described as 'glacial'. The reactions
                 to be investigated are:

                 A    pH of aqueous solution.

                 B    Reaction with sodium hydrogencarbonate solution.

                 C    Reaction with sodium.

                 D    Reaction with phosphorus pentachloride.

                 E    Reaction with 2,4-dinitrophenylhydrazine.

                 F    Triiodomethane (iodoform) reaction.

Chemicals :      Universal indicator, glacial ethanoic acid, saturated sodium hydrogencarbonate solution, limewater, sodium,
                 phosphorus pentachloride, 2 M ammonia solution, 2,4-dinitrophenylhydrazine solution, 10% I2 in KI(aq), 2 M
                 sodium hydroxide, sodium ethanoate, 0.1 M iron(III) chloride solution

Apparatus :      Forceps, filter papers, wood splint, spatula, safety spectacles

Procedure :      A.   pH of aqueous solution

                      1.   Into a test-tube, pour about 2 cm3 of distilled water and one drop of universal indicator solution. Shake
                           gently.
                      2.   Add a few drops of glacial ethanoic acid, shake gently and note your observations in the Table.

                 B. Reaction with sodium hydrogencarbonate solution

                      Into a test-tube, add about 1 cm3 of sodium hydrogencarbonate solution followed by a few drops of glacial
                      ethanoic acid. Shake gently and test any gas produced.

                 C. Reaction with sodium (WORK AT A FUME-CUPBOARD, WITH YOUR TEACHER PRESENT)

                      1.   Pour about 2 cm3 of glacial ethanoic acid into a dry test-tube in a rack standing in a fume-cupboard.
                      2.   Using forceps, pick up a 1 mm cube of sodium and blot it free of oil on some filter paper.
                      3.   Drop the clean piece of sodium into the glacial ethanoic acid. Test any gas evolved and note your
                           observations. Do not wash away the mixture until you are sure that the sodium has reacted completely. If
                           some sodium remain unreacted, add a little more glacial ethanoic acid; on no account add water.

                 D. Reaction with phosphorus pentachloride

                      1.   Pour about 1 cm3 of glacial ethanoic acid into a dry test-tube in a rack standing in a fume-cupboard.
                      2.   A little at a time, carefully add a spatula-measure of phosphorus pentachloride. Bring the wet stopper of an
                           ammonia bottle close to the mouth of the tube and note your observations.

                 E. Reaction with 2,4-dinitrophenylhydrazine

                      Into a test-tube, pour about 2 cm3 of 2,4-dinitrophenylhydrazine solution and about 5 drops of glacial ethanoic
                      acid. shake gently and note your observations.

                 F. Triiodomethane (iodoform) reaction

                      Into a test-tube, place ten drops of iodine solution, and five drops of glacial ethanoic acid, followed by sodium
                      hydroxide solution added dropwise until a light brown solution remains. Warm the solution gently. Shake the
                      tube gently and note your observations.
Results :
              Reaction                              Observations
              A. pH of aqueous solution
              B. Reaction with sodium
                  hydrogencarbonate solution
              C. Reaction with sodium
              D. Reaction with phosphorus
                  pentachloride
              E. Reaction with 2,4-
                  dinitrophenylhydrazine
              F. Triiodomethane reaction

Questions :   1.   Does ethanoic acid more closely resemble hydroxyl or carbonyl compounds in its reactions? Explain.
              2.   Which test indicates that ethanoic acid is a stronger acid than phenol?
              3.   Explain the fact that ethanoic acid is very soluble in water, whereas benzoic acid, C6H5CO2H, a solid, is only
                   slightly soluble in water.
Experiment :     18

Title :          Reactions of benzene, methylbenzene and nitrobenzene

Introduction :   Benzene is unsaturated compound. With the presence of p electrons, it is an ideal substrate of electrophilic
                 substitution. Depending on the presence of different substituent, the reactivity of the aromatic ring may be enhanced
                 or suppressed.


                 Precaution : Benzene is a toxic and carcinogenic substance, Avoid contact with its liquid and do not inhale its
                 vapour.

                 Nitrobenzene is a pale yellow liquid, insoluble in water and has a characteristic odour of bitter almond. Despite of
                 its pleasant smell, nitrobenzene is poisonous.

Chemicals :      Benzene, methylbenzene, nitrobenzene

Apparatus :

Procedure :      A. Reactivity of benzene and methylbenzene

                 1.   Bromination
                      To 10 drops of benzene in a test tube, add 1 cm3 of bromine water. Shake well. Is there any observable change?
                      To the same test tube, add a little iron filing. Is there any observable change?

                 2.   Reaction of KMnO4
                      To 1 cm3 of acidified KMnO4(aq) solution, add 1 cm3 of benzene, Shake well. Is there any observable change?
                      Warm the test tube gently. Is there any observable change?

                 3.   Nitration
                      Place 0.5 cm3 of conc. HNO3(aq) in a test tube. Add 0.5 cm3 of conc. H2SO4, shake and cool the test tube under a
                      stream of cold water. Add 5 drops of benzene into the mixed acid with cooling under a stream of cold water.
                      Allow the mixture to stand for a few minutes. Is there any observable change?

                 4.   Sulphonation
                      Place 4 drops of benzene in a test tube and then add 10 drops of conc. H2SO4. Warm the test tube gently until
                      the benzene has dissolved into the acid layer. Pour the mixture into a small beaker containing 10 cm3 of cold
                      satturated solution of sodium chloride. Is there any observable change?

                 Repeat procedure 1 to 5 by using methylbenzene instead of benzene.


                 B. Reaction of nitrobenzene

                 1.   Reduction with tin/hydrochloric acid
                      Place 3 drops of nitrobenzene in a test tube, add 1 cm3 of water and then 1 cm3 of concentrated HCl, followed
                      by 2 or 3 small pieces of tin. Warm. The benzenammonium chloride formed will be dissolved in the aqueous
                      layer.
                      Make the solution alkaline by adding dilute sodium hydroxide solution to liberate the benzeneamine

                 2.   Reduction with zinc/ethanoic acid
                      Repeat the reduction of nitrobenzene, using zinc dust and glacial ethanoic acid instead of tin and hydrocloric
                      acid. Heating is not required.

Questions :      1.   In general, is benzene or methylbenzene more reactive towards electrophilic substrate? Why is it more reactive
                      than the other one? Explain briefly.
Experiment :     19

Title :          Properties of amines

Objective :      To investigate the properties of amines

Introduction :   Amines are an important class of nitrogen containing organic compounds. They can be regarded as derivatives of
                 ammonia in which one or more of the hydrogen atoms in ammonia are replaced by alkyl or aryl groups. Compounds
                 containing the –NH2 group are important in the manufacture of drugs, dyes and nylon.

                 In this practical, the difference between ammonia, alkylamine and aromatic amine are compared.

                 Ammonia solution or ammonium salt is used for ammonia. Butan-1-amine is chosen for alkylamine because it is a
                 liquid and is not very volatile. Aniline is chosen for aromatic amine because it is also a liquid. It is colourless when
                 pure but is likely to be coloured due to atmospheric oxidation.


                 Compare the difference in
                 1. basic strength
                 2. solubility in neutral, acidic and alkaline medium
                 3. reaction with bromine water
                 4. reaction with nitric(III) acid at 0ºC and formation of diazo dye

Chemicals :      butan-1-amine, bezenamine (anilne), NH4Cl(s), NaNO2(s), conc. HCl(aq), ice, phenol, bromine water

Apparatus :

Procedure :      [Hazard Warning: Aniline is toxic and harmful because of skin absorption, butanamine is an irritant and is
                 extremely flammable. Avoid all skin contact.]

                 A. Reaction with water and basic strength.

                      1.   Shake two drops of butanamine and two drops to bezenamine separately with 2 cm3 of water. Place
                           ammonia solution into the third test tube. Test each of these solutions with pH paper.

                 B. Reaction with dilute hydrochloric acid

                      1.   Shake 2 drops of butan-1-amine and 2 drops of bezenamine separately with 2 cm3 of dilute hydrochloric
                           acid.
                      2.   Then add dilute sodium hydroxide to the solution of bezenamine in hydrochloric acid until the mixture is
                           alkaline.

                 C. Reaction with nitric(III) acid

                 (The preparation of HNO2 should be done at a very low temperature, otherwise it will decompose into NO2)

                      1.   Dissolve a small spatula measure of ammonium chloride in 3 cm3 of hot water and then cool down the
                           solution. Now add an equal amount of solid sodium nitrite. Observe any change.
                      2.   In another test tube, put 3 drops of butan-1-amine in a test tube and add concentrated hydrochloric acid
                           dropwise until a clear solution is formed and then cool down the solution. Dilute the mixture to 3 cm3 with
                           water, add a spatula measure of sodium nitrite.
                      3.   Repeat step 2 using bezenamine in place of butanamine.

                 D. Preparation of diazonium salt and azo dye

                      1.   Make a solution of 2 drops of bezenamine in 2 cm3 of dilute hydrochloric acid and add it to about 5 cm3 of
                           crushed ice / water mixture at 5 – 10°C. Add to this mixture a spatula measure of sodium nitrate(III) and
                           stir well to ensure that the solid dissolves.
                      2.   Dissolve a spatula measure of phenol (Corrosive - avoid skin contact) in 2 cm3 of dilute sodium
                           hydroxide solution. Cool this solution to below 5°C and add the diazonium solution prepared in step 1
                           drop by drop.

Results :        Draw a table to compare the differences in properties of ammonia (or ammonium salt), aliphatic amine and aromatic
                 amine.

				
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