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EXPERIMENT 3: STOICHIOMETRY
Procedure B: Stoichiometry of Several Salts

Pre-lab Questions:

1. Define:

   (a) stoichiometry

   
   (b) reactant

   
   (c) product

   
   (d) precipitation reaction

   
   (e) methathesis

   
   (f) balanced chemical equation

   
   (g) formula weight

   
   (h) limiting reactant

2. Balance the following equations, giving the reaction type at the right.

EXPERIMENT 3: STOICHIOMETRY
Procedure B: Stoichiometry of Several Salts

In this experiment you will use a piece of equipment called a well plate. A 24-well plate is shown in Figure I. This piece of equipment is made of clear plastic and, as shown in the figure, contains 24 wells. These wells are used to hold solutions. Each well can be identified using a combination of a letter and a number. In the figure, well B3 (2nd row- 3rd column) is labeled. In this experiment you will use a 24-well plate. The wells will be used to hold solutions. The size of these wells is small and only a small amount of reagent will be needed. Performing experiments on a 'microscale' is very economical, and considerably safer compared to large scale experiments.

EXPERIMENT 3: STOICHIOMETRY  Top
Procedure B: Stoichiometry of Several Salts

EQUIPMENT:
beaker, 50 mL......................2	micro-stirring rod ...........1
droppers.............................2	wash bottle...................1
plate, 24-well.......................1

Reaction I: Calcium nitrate and sodium oxalate

1. Label one 50 mL beaker "calcium nitrate" and one "sodium oxalate". Fill each with about 15 mL of the appropriate 0.10 M solution.

2. Place one dropper in each beaker. Be careful not to mix them up during the experiment.

3. Working across the first row in the well plate, put 4 drops of calcium nitrate solution in the first well, 8 drops in the second well, 12 drops in the third well, and so on, until you finish with 44 drops in the eleventh well. Be sure to use only the wells on the outside edge of the well plate. This will make your observations easier later on. Record the well number in Table 1.

4. Repeat step 3. with sodium oxalate, adding drops in the same manner, but in the reverse order, so that well #11 gets 4 drops, well #10 gets 8 drops, well #9 gets 12 drops, etc. Each well should contain a total of 48 drops when you finish.

5. Stir each of the wells with the micro-stirring rod, rinsing the rod with a wash bottle between stirs. Record your observations in the table.

6. While you are waiting for the precipitates to settle, calculate the ratio of drops of calcium nitrate to drops of sodium oxalate in each well.

Table 1

Questions:

1. After settling is complete, hold the well plate up, look through the side of the plate, and observe the precipitates. In which well is the larger amount of precipitate?

2. What is the ratio of calcium ion to oxalate ion in that well?

3. Balance the following equation:
   ____Ca(NO₃)₂ + ____Na₂C₂O₄ ____CaC₂O₄ + ____NaNO₃

4. What is the ratio of the coefficients of the reactants in the balanced equation?

5. How does this ratio compare to the ratio of reactants producing the maximum amount of product?

6. What is the limiting reactant in well #2?

   
   in well #10?

Reaction II: Silver nitrate and sodium chloride

Dispose of the chemicals in the well plate and beakers in the waste bottle(s)
provided. Rinse the plate, shaking the water out of it so that it is practically dry. Repeat the
6 step procedure described above using silver nitrate and sodium chloride as the two
reactants.

Table 2

Questions (continued):

7. After settling is complete, hold the well plate up, look through the side of the plate, and observe the precipitates. In which well is the larger amount of precipitate?

8. What is the ratio of silver ion to chloride ion in that well?

9. Balance the following equation:
   ____AgNO₃ + ____NaCl ____AgCl + ____NaNO₃

10. What is the ratio of the coefficients of the reactants in the balanced equation?

11. How does this ratio compare to the ratio you found experimentally?

12. What is the limiting reactant in well #2?

    
    in well #10?

Reaction III: Silver nitrate and sodium carbonate

Dispose of the chemicals in the well plate and beakers in the waste bottle(s)
provided. Rinse the plate, shaking the water out of it so that it is practically dry. Repeat the
6 step procedure described above using silver nitrate and sodium carbonate as the two
reactants.

Table 3

Questions (continued):

13. After settling is complete, hold the well plate up, look through the side of the plate, and observe the precipitates. In which well is the larger amount of precipitate?

14. What is the ratio of silver ion to carbonate ion in that well?

15. Balance the following equation:
    ____AgNO₃ + ____Na₂CO₃ ____Ag₂CO₃ + ____NaNO₃

16. What is the ratio of the coefficients of the reactants in the balanced equation?

17. How does this ratio compare to the ratio you found experimentally?

18. What is the limiting reactant in well #2?

    
    in well #10?

Reaction IV: Lead nitrate and potassium iodide

Dispose of the chemicals in the well plate and beakers in the waste bottle(s)
provided. Rinse the plate, shaking the water out of it so that it is practically dry. Repeat the
6 step procedure described above using lead nitrate and potassium iodide as the two
reactants.

Table 4

Questions (continued):

19. After settling is complete, hold the well plate up, look through the side of the plate, and observe the precipitates. In which well is the larger amount of precipitate?

20. What is the ratio of lead ion to iodide ion in that well?

21. Balance the following equation:
    ____Pb(NO₃)₂ + ____KI ____PbI₂ + ____KNO₃

22. What is the ratio of the coefficients of the reactants in the balanced equation?

23. How does this ratio compare to the ratio you found experimentally?

24. What is the limiting reactant in well #2?

    
    in well #10?

Reaction V: Silver nitrate and cobalt chloride

Dispose of the chemicals in the well plate and beakers in the waste bottle(s)
provided. Rinse the plate, shaking the water out of it so that it is practically dry. Repeat the
6 step procedure described above using silver nitrate and cobalt chloride as the two
reactants.

Table 5

Questions (continued):

25. After settling is complete, hold the well plate up, look through the side of the plate, and observe the precipitates. In which well is the larger amount of precipitate?

26. What is the ratio of silver ion to chloride ion in that well?

27. Balance the following equation:
    ____AgNO₃ + ____CoCl₂ ____AgCl + ____Co(NO₃)₂

28. What is the ratio of the coefficients of the reactants in the balanced equation?

29. How does this ratio compare to the ratio you found experimentally?

30. What is the limiting reactant in well #2?

    
    in well #10?

Reaction VI: Silver nitrate and nickel chloride

Dispose of the chemicals in the well plate and beakers in the waste bottle(s)
provided. Rinse the plate, shaking the water out of it so that it is practically dry. Repeat the
8 step procedure described above using silver nitrate and nickel chloride as the two
reactants.

Table 6

Questions (continued):

31. After settling is complete, hold the well plate up, look through the side of the plate, and observe the precipitates. In which well is the larger amount of precipitate?

32. What is the ratio of silver ion to chloride ion in that well?

33. Balance the following equation:

    ____AgNO₃ + ____NiCl₂ ____AgCl + ____Ni(NO₃)₂

34. What is the ratio of the coefficients of the reactants in the balanced equation?

35. How does this ratio compare to the ratio you found experimentally?

12. What is the limiting reactant in well #2?

    
    in well #10?

EXPERIMENT 3: STOICHIOMETRY Procedure B: Stoichiometry of Several Salts

Post-lab Questions:  Top

1. Based on your experimental data, does the stoichiometry of a product of a chemical reaction depend upon the amounts of reactant available to form the product? Cite experimental evidence to support your answer.

2. Does the stoichiometry of a salt depend upon the reactants used to produce that salt? Cite experimental evidence to support your answer.

3. Propane (C₃H₈), a liquid at high pressure, is often used as a fuel in rural areas where natural gas is not available. When it is released from its storage tank, it becomes a gas. Propane gas then reacts with oxygen (combustion) in a furnace to form carbon dioxide and water vapor. Write the balanced equation for this reaction.

4. The reusable booster rockets of the US space shuttle employ a mixture of aluminum and ammonium perchlorate for fuel. The reaction is:

   Al _(s) + NH₄ClO_{4 (s)} Al₂O_{3 s)} + AlCl_{3 (s)} + NO _(g) + H₂O _(g)

   (a) Balance the equation.

   
   (b) What mass of NH₄ClO₄ should be used in the fuel mixture for every kilogram of Al? (Show your work!)

5. (a) Write the balanced equation for the combustion of isooctane (C ₈ H₁₈ ) to produce water vapor and carbon dioxide gas.

6. (b) Assuming gasoline is 100% isooctane, with a density of 0.692 g/mL, what mass of carbon dioxide is produced by the combustion of 1.2 x 10¹⁰ gal of gasoline (the approximate annual consumption of gasoline in the US)?

7. Hydrogen cyanide is produced industrially from the reaction of gaseous ammonia, oxygen and methane.
   2NH₃(g) + 3O₂(g) + 2 CH₄(g) 2HCN(g) + 6H₂O(g)

   If 5.00 x 10³ kg of each of NH₃, O₂, and CH₄ react, what mass of HCN and of H₂O would be produced, assuming 100% yield?

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