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
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
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
Procedure : 1. Weight out about 1.3 g of anhydrous sodium carbonate accurately using the method of “weighing by
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
Burette contained :
Conical flask contained :
Indicator used :
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
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 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
Chemicals : 3M H2SO4(aq), 0.02M KMnO4(aq), H2C2O4·2H2O(s)
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.
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)
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
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
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
Trade Name: _______________ Manufacturer: _______________ Price: __________ Volume : __________
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.
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)
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
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
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
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
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
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.
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
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
[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
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
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 /
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 =
As for the concentration change in this experiment is constant,
time for methyl red to be bleached
ln ( ) = ln A + ln e-EA/RT
ln (constant) + ln = ln A -
ln t = [ln A - ln (constant)] -
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
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)
Experiment Time t / s 1 T / ºC T/K 1/T / K-1
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
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
(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
Reaction Time for precipitate to appear Observations
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
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
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
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
Experiment : 12
Title : Investigation of Some of the Properties of a Pair of Cis-Trans Isomers
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
Procedure : [Hazard Warning: Maleic acid is irritant, concentrated hydrochloric acid is corrosive, and bromine water is
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
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
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.]
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.
Reaction Hexane Cyclohexane Cyclohexene
A. Combustion least sooty most sooty
B. Action of bromine
1. in dark
2. in light
Identification of gas
Is there any gas
Suggest how to identify
the gas and carry out the
C. Action of bromine turns cloudy under light decolorizes and
water turns cloudy under light
D. Action of acidified turns colourless
E. Action of no reaction no reaction chars
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
(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
(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
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.
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
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
(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
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
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:
B. Condensation (Addition - elimination)
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)
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.
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
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
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.
Test Ethanal Propanone
A. Addition reaction with sodium
B. Condensation reaction with 2,4-
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
(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
Name Formula Boiling point Melting point of 2,4-
/ °C dinitrophenylhydrazone / ºC
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
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
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
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
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
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.
A. pH of aqueous solution
B. Reaction with sodium
C. Reaction with sodium
D. Reaction with phosphorus
E. Reaction with 2,4-
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
Precaution : Benzene is a toxic and carcinogenic substance, Avoid contact with its liquid and do not inhale its
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
Procedure : A. Reactivity of benzene and methylbenzene
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?
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?
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
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
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
2. Then add dilute sodium hydroxide to the solution of bezenamine in hydrochloric acid until the mixture is
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