STOICHIOMETRY II: LIMITING REACTANTS AND PERCENT …



STOICHIOMETRY II: LIMITING REACTANTS AND PERCENT YIELDS

Solve the following problems on a separate sheet of paper. You will need to balance the equations first.

1. For each of the following unbalanced chemical equations, suppose 10.0 g of each reactant is taken. Show by calculation which reactant is the limiting reactant. Calculate the mass of each product that is expected.

a. C3H8 + O2 ( CO2 + H2O (ans. O2 lim. / 8.26g CO2; 4.51g H2O)

b. Al + Cl2 ( AlCl3 (ans. Cl2 lim. / 12.5g AlCl3)

c. NaOH + CO2 ( Na2CO3 + H2O (ans. NaOH lim. / 13.3g Na2CO3; 2.25g H2O)

d. NaHCO3 + HCl ( NaCl + H2O + CO2 (ans. NaHCO3 lim. / 6.96g NaCl; 2.14g H2O; 5.24g CO2)

e. Al + I2 ( AlI3 (ans. I2 lim. / 10.7g AlI3)

2. Alkali metal hydroxides are sometimes used to “scrub” excess carbon dioxide from the air in closed spaces (such as submarines and spacecraft). For example, lithium hydroxide reacts with carbon dioxide according to the unbalanced chemical equation:

LiOH(s) + CO2(g) ( Li2CO3(s) + H2O(g)

Suppose a lithium hydroxide canister contains 155 g of LiOH. What mass of CO2 will the canister be able to absorb? If it is found that after 24 hours of use the canister has absorbed 102 g of carbon dioxide, what percentage of its capacity has been reached? (ans. 143g CO2; 71.3% cap.)

3. For the following equation:

Xe + 2F2 ( XeF4

What is the theoretical mass of xenon tetrafluoride that should form when 130. g of fluorine is reacted with xenon? What is the percent yield if only 310 g of XeF4 is actually isolated? (Theo. mass of XeF4 = 354g; 88% yield)

4. Titanium (IV) oxide is a white compound used as a coloring pigment. Solid titanium(IV) oxide can be prepared by reacting gaseous titanium(IV) chloride with oxygen gas. A second product of this reaction is chlorine gas.

TiCl4 + O2 ( TiO2 + Cl2

a. Suppose 6710 g of titanium(IV) chloride is reacted with 2450 g of oxygen. Calculate the maximum mass of titanium(IV) oxide that can form. (Hint: What is the limiting reactant?). (TiCl4 lim.; 2820g TiO2)

b. If the percent yield of TiO2 is 75%, what mass is actually formed? (2115g )

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