Chemistry I Practice Problems Stoichiometry
DIRECTIONS: Answer the following questions in your comp book showing all set-ups. Pay attention to significant figures and be sure to include units with your answer.
1. Calculate the number of moles of potassium chlorate, KClO3 (s), that must decompose to produce potassium chloride, KCl (s), and 1.80 moles of oxygen gas.
Ans. 1.20 moles
2. A camping lantern uses the reaction of calcium carbide, CaC2 (s), and water to produce acetylene gas, C2H2(g), and calcium hydroxide, Ca(OH)2(s). How many grams of water are required to produce 1.55 moles of acetylene gas? Ans. 55.8 g
3. How many moles of solid copper must react with silver nitrate, AgNO3, to produce 5.5 g of solid silver and copper(II) nitrate, Cu(NO3)2 (aq)? Ans. 0.025 mol
4. Hydrazine, N2H4 (l), and hydrogen peroxide, H2O2(l), react exothermically to produce nitrogen gas and water. When these are used as rocket fuel, how many grams of hydrogen peroxide are needed to react with 100.0 grams of hydrazine? Ans. 212.3 g
5. When excess of lead (II) carbonate, PbCO3(s), reacts with 0.0825 mol nitric acid, HNO3(aq), what mass of lead (II) nitrate, Pb(NO3)2(aq) will be formed? Ans. 13.7 g
6. The combustion of ammonia, NH3, produces NO and water according to the following balanced equation:
4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g)
What volume of oxygen at STP is needed to produce 50.0g of NO? Ans. 46.7 L
7. Sodium hydrogen carbonate, NaHCO3, decomposes to form sodium carbonate, Na2CO3, carbon dioxide and water. What volume of carbon dioxide will be produce at STP from 26.8 g of sodium hydrogen carbonate? Ans. 7.02 L
8. Sodium reacts instantly with water to give hydrogen gas and a solution of sodium hydroxide. How many grams of sodium metal are needed to give 7.81 g of hydrogen by this reaction?
2 Na + 2 H2O → 2 NaOH + H2 Ans. 178g
9. Zinc metal reacts with hydrochloric acid, HCl, to produce zinc chloride, ZnCl2, and hydrogen gas. What volume of hydrogen gas at STP will be produced when 0.15 moles HCl reacts with excess zinc? Ans. 1.68 L
10. Oxygen can be produced by heating HgO. The other product is mercury, Hg. If 6.47 g of oxygen are collected, how many grams of mercury are also produced? Ans. 81.1 g