Chapter 10 Stoichiometry

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Chapter 10 Stoichiometry Powered By Docstoc
					Chapter 10 Stoichiometry
Exercise 1
Show your work.

For questions 1 - 4 use the equation:
            2Mg + O2 → 2MgO

1. Calculate the number of moles of oxygen needed to reaction with 6 moles
of Mg.

2. Calculate the number of moles of MgO produced when 0.4 moles of
oxygen react.

3. Calculate the number of moles of MgO produced when 32 g of oxygen
react.

4. Calculate the grams of oxygen needed to produce 6 g of MgO.


For questions 5 - 9 use the equation:
            2C6H6 + 15O2 → 12CO2 + 6H2O

5. Calculate the number of moles of oxygen required to reaction with 5.00
mole of C6H6.

6. Calculate the mole of CO2 produced when 0.75 moles of O2 react.

7. Calculate the number of grams of C6H6 needed to produce 50.0 g of
water.

8. Calculate the number of moles of water produced when 75 g of oxygen
react.

9. Calculate the grams of C6H6 need to produce 25 g of CO2.

10. Calculate the number of grams of H2SO4 produced when 27 g of water
react with an excess of SO3.
             H2O + SO3 → H2SO4

                                         H. Cannon, C. Clapper and T. Guillot
                                                           Klein High School
                                                             Stoichiometry




Exercise 2
Show your work.

1. Calculate the number of moles of barium sulfate that can be prepared
from 60.0 g of barium chloride.
            BaCl2 + Na2SO4 —> BaSO4 + 2NaCl

2. Calculate the number of moles of calcium chloride that would be
necessary to prepare 85.0 g of calcium phosphate.
             3CaCl2 + 2Na3PO4 —> Ca3(PO4)2 + 6NaCl

3. Sodium chloride (0.400 Mole) is allowed to react with an excess of
sulfuric acid. How many moles of hydrogen chloride could be formed?
              2NaCl + H2SO4 —> Na2SO4 + 2HCl

4. If 0.380 mole of barium nitrate is allowed to react with an excess of
phosphoric acid, how many moles of barium phosphate could be formed?
             3Ba(NO3)2 + 2H3PO4 —> Ba3(PO4)2 + 6HNO3

5. Calculate the number of grams of carbon dioxide produced from the
burning of 1.65 moles of C3H8.
             C3H8 + 5O2 —> 3CO2 + 4H2O

6. How many moles of hydrogen molecules could be produced by the
reaction of 3.40 moles of sodium atoms with water?
             2Na + 2H2O —> 2NaOH + H2

7. How many moles of HI would be necessary to produce 2.20 moles of
iodine, according to the following balanced equation:
             10 HI + 2KMnO4 + 3H2SO4 —> 5 I2 + 2MnSO4 + K2SO4 +
8H2O

8. Calculate the number of grams of zinc chloride that can be prepared from
34.0 g of zinc.
             Zn + 2HCl —> ZnCl2 + H2




                                                                    10-2
                                                           HC/CC/TG KHS
                                                              Stoichiometry

Exercise 3
Show your work.

   1. If 20.0 g zinc reacts with excess hydrochloric acid, how many grams
      of zinc chloride are produced?
                  Zn + HCl ZnCl2 + H2

2. How many grams of chlorine must be reacted with excess sodium iodide
if 10.0 g sodium chloride is needed?
                   NaI + Cl2 NaCl + I2

   3. How many grams of oxygen are produced in the decomposition of
      5.0 g of potassium chlorate? KClO3 KCl + O2

   4. How many grams of copper are required to replace 4.0 g of silver
      nitrate which is dissolved in water?
                  Cu + AgNO3 Cu(NO3)2 + Ag

   5. If excess ammonium sulfate reacts with 20.0 g of calcium hydroxide,
      how many grams of ammonia are produced:
                 (NH4)2SO4 + Ca(OH)2 CaSO4 + NH3 + H2O

   6. If excess sulfuric acid reacts with 30.0 g of sodium chloride, how
      many grams of hydrogen chloride are produced?
                  NaCl + H2SO4 HCl + Na2SO4

   7. How much silver phosphate is produced if 10.0 g of silver acetate is
      reacted with excess sodium phosphate?
                 AgC2H3O2 + Na3PO4 Ag3PO4 + NaC2H3O2

   8. What amount of sodium hydroxide is needed to completely neutralize
      25.0 g of sulfuric acid? NaOH + H2SO4 Na2SO4 + H2O

   9. Copper (II) sulfate pentahydrate may be heated to drive off the water
      of hydration. If 5.0 g of water is produced, what was the mass of the
      original compound? CuSO4 ⋅5H2O CuSO4 + 5H2O

   10. How many moles and how many grams of magnesium phosphate are
       produced by starting with 100.0 g of phosphoric acid and an excess of
       magnesium carbonate?
                                                                     10-3
                                                            HC/CC/TG KHS
                                                                Stoichiometry

                 H3PO4 + MgCO3       Mg3(PO4)2 + CO2 + H2O
Exercise 4

1. Aluminum and iron (III) oxide react according to the following equation
                     Al + Fe203- > A1203 + Fe
How much iron would be produced from 52.5g of iron (III) oxide?


2. Ammonia is produced according to the following equation:
          N2 + H2 NH3
How many kilograms of nitrogen would be required to produce 556
kilogram5 of ammonia?


   3. Calcium carbide is made in an electric furnace according to the
      ecuation:
         CaO + C CaC2 + CO
   75.5 kg of CaO will produce how many kilograms of calcium carbide?


   4. In the equation        Fe + H2O Fe2O3 + H2
235g of iron will produce how many grams of iron (III) oxide?


   5. Calcium chloride and water react according to the following equation
          CaCl2 + H2O CaO + HC1
How much hydrogen chloride would be produced from 37 4g of calcium
chloride?

   6. how many grams. of iron (ii) bromide will be: neeced to react with an
      excess of potassium phosphate to produce 17.1g of solid iron(ii)
      phosphate?

7. How many grams of oxygen gas are required to react with 37.8g of solid
zinc iodide, to produce solid iodine and solid zinc oxide?



8. How many grams of silver can be produced by the reaction 5.05g of
silver nitrate with excess copper?
                                                                    10-4
                                                           HC/CC/TG KHS
                                                                 Stoichiometry




9. What mass of barium chloride will be needed to react completely with
113g of aluminum sulfate to produce barium sulfate and aluminum chloride?



10. What mass of carbon dioxide will be produced by the combustion of
40.09 of pentane, C5H12?



11. How many grams of copper (II) nitrate would be produced from 4.30g of
copper metal reacting with excess hydrogen nitrate?



12. When copper (II) nitrate reacts with sodium hydroxide, copper (II)
hydroxide is produced along with sodium nitrate. How many grams of
copper (II) hydroxide can! be prepared from 12.7g of copper (II) nitrate and
excess sodium hydroxide?



13. When copper (II) hydroxide is heated it decomposes to black copper (II)
oxide and water. How many grams of copper (II) oxide will be formed from
the decomposition of 6.99g of copper(II) hydroxide?

14. When 5.37g of the black copper(II) oxide is mixed with excess hydrogen
sulfate, the solution turns a clear blue, indicating the formation of copper (I)
sulfate. How many grams of copper (II) sulfate will be formed in this double
displacement reaction?



15. If an excess of zinc metal is placed in a copper (II) sulfate solution, the
zinc will displace the copper. if 10.8g of copper(II) sulfate are reacted, how
many grams of copper metal will be recovered from the solution?

                                                                        10-5
                                                               HC/CC/TG KHS
                                                              Stoichiometry

Exercise 5
1. Calculate the mass of O2 produced if 2.50 g of KC1Oa decomposes to
produce potassium chloride and oxygen.


2. If 20.0 g of magnesium react with excess hydrochloric acid, how many
grams of magnesium chloride are produced?


3. How many grams of chlorine gas must be reacted with excess sodium
iodide if 10.0 g of sodium chloride are needed?

4. How many grams of oxygen are produced in the decomposition of 5.00 g
of potassium chlorate?


5. What mass of copper is required to replace silver from 4.00 g of silver
nitrate? The products are copper (II) nitrate and silver.


6. If excess ammonium sulfate reacts with 20.0 g of calcium hydroxide, how
many grams of ammonia are produced? The other products are water and
calcium sulfate.


7. If excess sulfuric acid (H2SO4.) reacts with 30.0 g of sodium chloride,
how many grams of hydrogen chloride are produced?


8. How much silver phosphate is produced if 10.0 g of silver acetate react
with excess sodium phosphate?


9. How many grams of sodium hydroxide are needed to completely
neutralize 25.0 g of sulfuric acid?


10. Molten iron and carbon monoxide are produced in a blast furnace by the
reaction of iron (III) oxide and coke (carbon). If 25.0 kg of pure iron (III)
oxide are used, how much iron can be produced?
                                                                     10-6
                                                            HC/CC/TG KHS
                                                              Stoichiometry

Exercise 6 Show your work

1. Copper oxide is reduced by ammonia according to the following
   equation:
           3CuO + 2 NH3 ---> 3Cu + N2 + H2 O

What mass of nitrogen in grams is. obtained by the reduction of 120g of
CuO?

2. Sulfur may be oxidized by potassium dichromate according to the
    following equation

        2K2 Cr2 O7 + H2 O + 3S ------> 3SO2 + 4KOH        +2.Cr2 O3

What mass of sulfur wil1 be oxidized by 12 grams of potassium dichromate?

3. How many grams of BaSO4 may be precipitated from a solution
   containing .314 grams of sodium sulfate?

            BaC12 + Na2 SO4 ----- 2NaC1 + BaSO4

4. Consider the following equations:

       3CaC12 + 2K3 PO4 -----> Ca3 (PO4)2 + 6KCl

a. 87g of CaC12 will produce      ? _ grams of KC1.

b. How many grams of K3 PO4 can 132g of CaC12 react?



5. When the neutralization of H3PO4 with Ca(OH)2 occurs, then the
   following equation exists.

      H2PO4 + Ca (OH)2 - - - - -> Ca 3 ( PO4 ) 2 + H2 O

      a) 8.4 moles H3 PO4 produces _?__ moles of water.

     b) 18 moles of Ca3 (PO4)2 is produced from ___?__ moles of
Ca(0H)2.
                                                                      10-7
                                                             HC/CC/TG KHS
                                                               Stoichiometry

6. Solve the following from the given equation:
  Bi2(SO4)3 + 6NH4 OH ----> 2Bi(OH)3 + 3(NH4)2SO4

 If you are given 352g of Bi2(SO4)3, then:
 a) Calculate the number of moles of Bi2 (SO4)3.
 b) How many moles of Bi(OH)3 will be produced from the 352g
    of Bi2 (S04)3?



c) How many moles of NH4 OH will react with the 352g of Bi2 (SO4)3?


7. Methane gas can be prepared in the laboratory by the following reaction:

             A14 C3 + 12H2 O --> 3CH4 + 4Al(OH)3

a) What weight of Al4C3 is needed to prepare 1.8 moles of aluminum
   hydroxide?

b) How many grams of methane will be produced from 30g of water?.

8. What weight of oxygen is needed to burn 31 grams of propane gas?

           C3H8 +    O2       CO2 +   H2 O (unbalanced)


9. In the process of photosynthesis, plants use carbon dioxide and water to
     produce sugars according to the over-all reaction.

           11 H2 O + 12 C02      C12 H22 O11 ?

   a) What weight of carbon dioxide is used by a plant in making 254g of
sugar C12 H22 O11 ?


   b) How many grams of oxygen will 8O grams of carbon dioxide
   produce?

Exercise 7 Show your work
                                                                      10-8
                                                             HC/CC/TG KHS
                                                               Stoichiometry



QUESTIONS 1,2,3:REFER TO THE FOLLOWING EQUATION:
          Cu + HNO3 Cu(NO3)2 + NO + H2O
1. If you could drop 12 atoms of copper into a beaker containing hydrogen
    nitrate, how many molecules of nitrogen dioxide would be produced?


2. Calculate the number of moles of water produced when 6.6 moles
of copper (II) nitrate are formed on the reaction.


3. How many grams of copper would be needed to react with 4 moles of
   hydrogen nitrate?


4. 25g of potassium chlorate is to be decomposed by heating. How many
   grams of oxygen can be prepared?       KClO3 ---> KC1 +        O2


5. In a reaction between sulfur and oxygen, 80g of sulfur dioxide is formed.
    How many grams of sulfur were burned?


6. How many grams of hydrogen are required to completely convert 25g of
   hot magnetic iron (III) oxide (Fe2O3) to elementary iron?
                    Fe2 O3 + H2          Fe    + H2 O

7. How many grams of chlorine will it take to react with 68g of potassium
   iodide?

8. Approximately 130g of zinc was dropped into a solution con-
taining HC1. How many moles of hydrogen were produced?
                   Zn + HC1          ZnC12 +       H2


9. Suppose 10g of iron (II) sulfide is treated with enough hydrogen chloride
   to complete the reaction. How many grams of hydrogen sulfide gas could
   be collected?     FeS + HC1              FeC12 + H2 S


                                                                      10-9
                                                             HC/CC/TG KHS
                                                             Stoichiometry

10. A portable hydrogen generator utilizes the reaction:
           CaH2 + 2H2O        Ca(OH)2
How many grams of hydrogen can be produced by a 50g cartridge of CaH2?



11. How much ferric oxide will be produced by the complete oxidation of
    100.0 grams of iron? The reaction is:     Fe + O2          Fe2O3



12. Chloropicrin, CC13 NO2 , can be made cheaply for use as an
insecticide by a process which utilizes the reaction:
              CH3 NO2 + 3C12               CC13 NO2 + 3HC1
How much nitromethane, CH3 NO2, is needed to form 500.0g of
chloropierin?



13. Ethyl alcohol (C2 H5 OH) is made by the fermentation of glucose
    (C6H12O6 ) as indicated by the equation:

              C6H12O6           2C2H12OH      + 2CO2
How many grams of carbon dioxide gas can be produced from 60.0g of ethyl
alcohol?


14. One of the reaction used in the petroleum industry for improving the
    octane rating of fuels is:      C7H14         C7H8 + 3H2
If 56.8 grams of heptane (C 7H14) is used how much hydrogen is produced?




15. When copper is heated with an excess of sulfur, copper (I) sulfide is
   produced. How many grams of copper (I) sulfide could be produced from
   100 grams of copper?




                                                                   10-10
                                                           HC/CC/TG KHS
                                                                Stoichiometry

Limiting Reactants
1. If 20.0g of sodium hydroxide react with 30.0 g of sulfuric acid to produce
   sodium sulfate, which reactant is limiting? How much sodium sulfate is
   produced?


2. What reactant is limiting is 3.00 g of chlorine gas reacts with 25.0 g of
   sodium bromide to produce bromine gas? How much sodium chloride is
   produced?


3. If 20.0 g of potassium hydroxide reacts with 15.0 g of ammonium sulfate,
   how much ammonia is produced (the other products are potassium sulfate
   and water). Which reactant is limiting?


4. If a drain cleaner contains 455 g of sodium hydroxide and 45.0 grams of
   aluminum shavings, when this is reacted with water, how much hydrogen
   gas would be produced (the other product is sodium aluminate (AlO2 -1)?
   What is the limiting reactant?



5. If 23.4 g of sodium hydroxide reacts with 50.0 g of hydrochloric aced,
   how much water will be produced? What is the limiting reactant?



6. How much chromium (III) hydroxide will be produced by the reaction of
   2.37 g of silver nitrate with 2.00 g of sodium hydroxide?



7. When 84.1 g of magnesium oxide reacts with 47 g of water, how much
   magnesium hydroxide is formed? What is the limiting reactant?



8. If 261 g of potassium chloride reacts with 543 g of silver nitrate, how
   much silver chloride will be produced?
                                                                     10-11
                                                             HC/CC/TG KHS
                                                                Stoichiometry




9. Calculate the number of grams of carbon dioxide which will be formed in
   the reaction between 10.0 grams of propane (C3H8) and 10.0 grams of
   oxygen.



10. In the reaction single replacement reaction between gold III sulfide and
    hydrogen gas if the initial amount of Au2S3 is 500.20 g and the initial
    amount of H2 is 5.67g, what is the final mass of gold?



11. In a reaction between magnesium nitride and water, magnesium
    hydroxide and ammonia (NH3) are produced. If the initial amount of
    Mg3N2 is 58.1g and the initial amount of H2O is 20.4g, what is the final
    mass of ammonia?



12. In the reaction 2C3H6 + 2NH3 + 3O2 2C3H3N + 6H2O, if the initial
    amounts are C3H6: 22.5g, NH3: 20.6 g, and O2: 18.1 g, what are the final
    amounts of each product?


13. What is the limiting reactant when 19.9g of CuO are exposed to 2.02g of
    H2 according to the following equation?
      CuO(s) + H2(g) Cu(s) + H2(g)
    How many grams of Cu are produced?


14. Metallic magnesium reacts with steam to produce magnesium hydrocise
    and hydrogen ga. If 16.2 g of Mg are heated with 12.0 g of H2O, what is
    the limiting reactant? How many grams of each product will be
    produced?




                                                                     10-12
                                                             HC/CC/TG KHS
                                                             Stoichiometry

Percent Yield

   1. In the double displacement reaction between citric acid and plumbic
      hydroxide, how much lead (IV) citrate would be produced from 87.6g
      of citric acid and 111g of plumbic hydroxide if the percent yield is
      83%?


   2. When potassium chromate is added to 0.500 g of silver nitrate, solid
      silver chromate is formed. If the mass of the silver chromate formed
      is 0.455 g, what is the percent yield of the reaction?


   3. Magnesium chloride can be produced by reacting magnesium
      hydroxide with hydrochloric acid. If 200.0 g of magnesium chloride
      is produced from 185 g of hydrochloric, what is the percent yield of
      the reaction?



   4. In the double displacement reaction between acetic acid and plumbic
      hydroxide, how much lead (IV) acetate would be produced from 76.8g
      of acetic acid if the percent yield is 91%?



   5. When 84.8 g of ferric oxide reacts with an excess of carbon
      monoxide, 54.3 g of iron is produced, along with carbon dioxide gas.
      What is the percent yield of this reaction?



   6. Chlorobenzene, C6H5Cl, is used in the production of many important
      chemicals, such as aspirin, dyes and disinfectants. One industrial
      method of preparing chlorobenzene is to react benzene. C6H6, with
      chloring, as represented by the following equation.
                C6H6 (l) + Cl2 (g) C6H5Cl (s) + HCl (g)
      When 36.8g of C6H6 react with an excess of Cl2, the actual yiel2os
      e;ectrp;yzed to produce Mg and Cld of C6H5Cl is 38.8 g. what is the
      percent yield of C6H5Cl?
                                                                   10-13
                                                           HC/CC/TG KHS
                                                            Stoichiometry




7. Magnesium is obtained from sea water. Ca(oh)2 is added to sea water
   to precipitate Mg(OH)2. The precipitate is filtered and reacted with
   HCl to produce MgCl2. the MgCl2. If 185.0 g of magnesium are
   recovered from 1000.0 g of MgCl2, what is the percent yield for this
   reaction?



8. Aluminum hydroxide is often present in antacids to neutralize
   stomach acid (HCl). If 14.0 g of Al(OH)3 is present in an antacid
   tablet, determine the theoretical yield of aluminum chloride produced
   when the tablet reacts with stomach acid. If the actual yield of
   aluminum chloride from this tablet is 22.0 g, what is the percent
   yield?
      Al(OH)3(s) + 3HCl (aq) AlCl3(aq) + 3H2O (l)



9. Zinc reacts with iodine in a synthesis reaction. Write the balanced
   chemical equation for the reaction. Determine the theoretical yield if a
   125.0 g sample of zinc was used. Determine the percent yield if
   515.6g is recovered.



10. Upon heating, calcium carbonate decomposes into calcium oxide and
    carbon dioxide gas. What is the theoretical yield of CO2 if 235.0 g of
    CaCo3 is heated? What is the percent yield of CO2 if 97.5 g of CO2 is
    collected?


11. Chlorine can be prepared by the reaction of manganese )II) oxide with
    hydrochloric acid.
    MnO2(s) + HCl (aq)        MnCl2 (aq) + Cl2 (g) + H2O (l)
    Balance the equation and determine the percent yield of chlorine if
    86.0 g of MnO2 and 50.0 g of HCl react to form 20.0 g of chlorine.


                                                                  10-14
                                                          HC/CC/TG KHS
                                                              Stoichiometry




Exercise 8
Show your work.

Indicate if the following are endothermic or exothermic:

1. C + H20     C02 + 2H20 - 163 kJ

2. C+ 1/202 - 121 kJ    CO


3. CO+ 1/202      CO2 +283 kJ


4. N204 + 58 kJ    2NO2

5. Given the following balanced equation:
         H2 + F2 ---> H2F2 + 5.27 x 105 J
a. Is the reaction exothermic or endothermic?

b. Calculate the number of joules of heat energy produced in the reaction of
37.0 g of fluorine gas with sufficient hydrogen gas.



6. Given the following balanced equation:
         O2 + 2F2 ---> 2OF2 - 4.60 x 104 J

a. Is the reaction exothermic or endothermic?

b. Calculate the number of grams of fluorine gas needed for the reaction
with 8.74 x 103 J of heat energy and sufficient oxygen gas.




                                                                    10-15
                                                            HC/CC/TG KHS
                                                              Stiochiometry
                                                       Exercise mass-energy
Exercise 9 Mass-Energy Problems

1. A rocket fuel is prepared by reacting hydrazine and dinitrogen tetroxide
   according to the equation:
      2N2 H4 + N2 O4           3N2 + 4H2 + 2400 kJ
Calculate the heat released when 3200 grams of hydrazine are consumed in
the rocket engine.


2. The dissociation of ammonia into its elements is an endothermic reaction
   that absorbs 92.2kj of energy per mole of nitrogen. How much energy
   will be required to decompose 85.0 grams of ammonia?



3. Given the equation: Fe2 O3 + 2Al          Al2 O3 + 2Fe + 852 kJ
How much energy is produced by the reaction of 16.0 grams of
iron (III) oxide with excess aluminum metal?



4. When hydrogen peroxide is placed on a cut knee it decomposes
   spontaneously into water and oxygen gas, releasing 200 kJ of heat per
   mole of oxygen. How much energy will be released when 34.0 grams of
   hydrogen peroxide decomposes?



5. Manganese will react with hydrochloric acid to produce hydrogen gas
   according to the reaction:

         Mn + 2HCl       MnCl2 + H2 + 221 kJ
How much energy will be released when 5.494 g of manganese reacts
completely?




                                                                    10-16
                                                            HC/CC/TG KHS
                                                               Stiochiometry
                                                        Exercise mass-energy
               Molar Relationship in a Chemical Reaction
Problem: To compare the amount of sodium bicarbonate that reacts with
hydrochloric acid to the amount of sodium chloride produced.

Procedure:
  1. Determine the mass of a clean evaporating dish and watch glass
     (together)
  2. Weigh out approximately 3 grams of sodium bicarbonate into the dish
     (record exact amount)
  3. Obtain approximately 6 ml of hydrochloric acid. This is a small test
     tube filled to the lower edge of the marking spot. The exact amount is
     not important, as this reactant will be in excess.
  4. With a dropper, slowly and carefully add the acid to the dish through
     the space between the lip and the watch glass. Add acid only until the
     reaction stops and you are left with a clear colorless solution that is no
     longer bubbling.
  5. Tilt the dish to be sure the acid has reached all of the solid
  6. Place the dish with watch glass cover on a ring above a burner. Heat
     slowly to keep at a low boil until the solution is dry. Spattering is the
     result of heating too fast, and will result in the loss of some of your
     product. Heat until NO liquid remains on the watch glass cover.
  7. Let the apparatus cool and determine it’s mass again.
  8. Time permitting, reheat to boil away any water left, coo, reweigh.
  9. Clean all laboratory apparatus and return to proper storage area.

Questions to consider:
  1. How many moles of sodium bicarbonate were used?
  2. Using the equation NaHCO3 + HCl NaCl + H2O + CO2, predict
     the moles and grams of sodium chloride you should have produced.
  3. How many moles of sodium chloride were actually produced?
  4. What is your percent experimental error?
  5. Do your results verify the stoichiometry of the reaction? Explain
  6. Do your results verify the Law of Conservation of Mattter?




                                                                      10-17
                                                              HC/CC/TG KHS
                                                                Stoichiometry



Chapter 10 Quantitative Analysis Lab

Objective: To produce a specific quantity of lead (II) chromate by the
reaction of lead (II) nitrate with potassium chromate; and to demonstrate the
Law of Conservation of Matter and the stoichiometric relationship of the
reaction.

Procedure: (remember to record all measurements and observations in your
lab book`)

   1. Prelab calculations
   a. Choose a number between 1.00 and 1.50. This is the number of grams
   of lead (II) chromate you will try to make.

   b. Calculate the number of moles of lead chromate equal to your number
   of grams.

   c. Calculate the number of moles of lead(II) nitrate required to give the
   above number of moles of lead chromate.

   d. Calculate the number of grams of potassium chromate required
   to-give the above number of moles of lead (II) chromate?

   2. Lab - Day 1
   a. Carefully weigh out exactly the calculated amount of lead (II) nitrate.
   Dissolve in about 25 ml of distilled water in a 100 ml beaker. The exact
   amount of water is not critical since it will be removed by drying.

   b. In a 150 ml beaker carefully weigh the calculated amount of
   potassium chromate. Dissolve in about 25 ml of water. Again the exact
   amount of water is not critical to the reaction.

   c. Combine the two solutions to begin the reaction, being certain to rinse
   all of the solution from the beaker.

   d. Stir the reaction for 3-4 minutes to coagulate the precipitate.

   e. Filter the solution.

                                                                      10-18
                                                              HC/CC/TG KHS
                                                                Stoichiometry

   f. Spread the filter paper out to dry overnight.

   g. Time permitting, evaporate the contents of the beaker and reweigh
3. Lab - Day 2

   a. Determine the mass of both products of the reaction.

   b. Calculate the number of moles of lead (II) chromate and potassium
   nitrate produced, and correlate this to the stoichiometry of the equation.
   (Divide each of these by the moles of lead (II) nitrate. To what numbers
   in the equation should these relate?

   c. Calculate the number of grams of potassium nitrate and lead (II)
   chromate produced. Have you illustrated the conservation of mass?
   Explain

   d. Calculate your percent yield.

   e. If your yield was below 98% or above 101%, suggest possible
      explanations.


 Lab report – include a list of all measurements, show work on all
calculations (number these to correlate with the steps in the procedure, don't
forget to label with units). There should be a total of 8 calculations in your
report (follow the steps in the procedure). Your grade will be based on
laboratory accuracy (from your percent yield) as well as mathematical
accuracy (from your calculations work).




                                                                      10-19
                                                              HC/CC/TG KHS
 Stoichiometry
  Exercise Lab




        10-20
HC/CC/TG KHS