Mass–mass calculations Transitional Reasoning Download PDF

Questions

1. 1.

   An automotive safety engineer tests a rapid-inflation airbag canister that generates nitrogen gas through the thermal decomposition of solid sodium azide according to the balanced equation $2\text{NaN}_3(s) \rightarrow 2\text{Na}(s) + 3\text{N}_2(g)$. During a controlled crash simulation, a canister containing 130.0 g of pure sodium azide completely decomposes. Based on stoichiometric principles, what mass of nitrogen gas is produced to inflate the airbag? (Molar masses: $\text{N} = 14.0\text{ g/mol}$, $\text{Na} = 23.0\text{ g/mol}$)

   • A) 42.0 g
   • B) 56.0 g
   • C) 84.0 g
   • D) 126.0 g
2. 2.

   In an underwater research vessel, canisters of solid lithium hydroxide are utilized to remove exhaled carbon dioxide from cabin air according to the reaction $2\text{LiOH}(s) + \text{CO}_2(g) \rightarrow \text{Li}_2\text{CO}_3(s) + \text{H}_2\text{O}(l)$. During a mission simulation, a crew member generates exactly 88.0 g of carbon dioxide gas over a test period. Based on stoichiometric principles, what is the minimum mass of lithium hydroxide required to completely absorb this amount of carbon dioxide? (Molar masses: $\text{H} = 1.0\text{ g/mol}$, $\text{Li} = 7.0\text{ g/mol}$, $\text{C} = 12.0\text{ g/mol}$, $\text{O} = 16.0\text{ g/mol}$)

   • A) 96.0 g
   • B) 48.0 g
   • C) 24.0 g
   • D) 192 g
3. 3.

   A materials chemist evaluates a limestone sample for industrial cement manufacturing by heating calcium carbonate until complete thermal decomposition occurs according to the balanced equation $\text{CaCO}_3(s) \rightarrow \text{CaO}(s) + \text{CO}_2(g)$. In an open crucible, a 25.0 g sample of pure calcium carbonate is heated until the reaction is complete and no more gas evolves. Based on stoichiometric principles, what mass of solid calcium oxide remains in the crucible? (Molar masses: $\text{C} = 12.0\text{ g/mol}$, $\text{O} = 16.0\text{ g/mol}$, $\text{Ca} = 40.0\text{ g/mol}$)

   • A) 25.0 g
   • B) 11.0 g
   • C) 7.00 g
   • D) 14.0 g
4. 4.

   Railway maintenance crews use the highly exothermic thermite reaction to weld sections of steel rail together: $2\text{Al}(s) + \text{Fe}_2\text{O}_3(s) \rightarrow \text{Al}_2\text{O}_3(s) + 2\text{Fe}(l)$. To join a track joint, a welding technician completely reacts 48.0 g of iron(III) oxide with an excess of aluminum powder. What mass of molten iron is produced by this process? (Molar masses: $\text{Al} = 27.0\text{ g/mol}$, $\text{O} = 16.0\text{ g/mol}$, $\text{Fe} = 56.0\text{ g/mol}$)

   • A) 16.8 g
   • B) 33.6 g
   • C) 67.2 g
   • D) 24.0 g
5. 5.

   A spacecraft life-support engineer evaluates a portable heating unit that operates by the complete combustion of propane according to the balanced equation $\text{C}_3\text{H}_8(g) + 5\text{O}_2(g) \rightarrow 3\text{CO}_2(g) + 4\text{H}_2\text{O}(g)$. During a test run inside a sealed environment, exactly 22.0 g of propane is burned completely in the presence of excess oxygen. Based on stoichiometric principles, what mass of water vapor is collected from this reaction? (Molar masses: $\text{H} = 1.0\text{ g/mol}$, $\text{C} = 12.0\text{ g/mol}$, $\text{O} = 16.0\text{ g/mol}$)

   • A) 36.0 g
   • B) 66.0 g
   • C) 9.0 g
   • D) 88.0 g