Activity 3.20:
Solving numerical stoichiometry problems
[Relative atomic mass: H = 1, C = 12, O = 16, Cl = 35.5, Ca = 40, Fe = 56, Zn = 65; Avogadro constant, NA : 6.02 × 1023 mol–1; Molar volume = 22.4 dm3 mol–1 at STP or 24 dm3 mol–1 at room conditions]
1. Decomposition of calcium carbonate by heating is as follows:
$$ \mathrm{CaCO}_3(\mathrm{~s}) \underset{\Delta}{\rightarrow} \mathrm{CaO}(\mathrm{~s})+\mathrm{CO}_2(\mathrm{~g}) $$
What is the mass of calcium carbonate required to produce 1.2 dm3 of carbon dioxide gas, CO2 at room conditions?
2. Zinc reacts with hydrochloric acid as follows:
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
What is the mass of zinc that should be used to produce 0.5 mol of hydrogen gas, H2?
3. A sample of iron(III) oxide, Fe2O3 is heated in a stream of excess hydrogen gas, H2 to produce 5.6 g of iron metal according to the following equation:
Fe2O3(g) + 3H2(g) → 2Fe(s) + 3H2O(l)
Calculate the mass of the iron(III) oxide sample.
4. Nitrogen and hydrogen gases react according to the following equation:
N2(g) + 3H2(g) → 2NH3(g)
How many molecules of ammonia, NH3 are produced if 6.72 dm3 of nitrogen gas at STP reacts completely with hydrogen gas?
Answer:
1. 5 g
2. 32.5 g
3. 8 g
4. 3.612 × 1023 ammonia molecules
Solving numerical stoichiometry problems
[Relative atomic mass: H = 1, C = 12, O = 16, Cl = 35.5, Ca = 40, Fe = 56, Zn = 65; Avogadro constant, NA : 6.02 × 1023 mol–1; Molar volume = 22.4 dm3 mol–1 at STP or 24 dm3 mol–1 at room conditions]
1. Decomposition of calcium carbonate by heating is as follows:
$$ \mathrm{CaCO}_3(\mathrm{~s}) \underset{\Delta}{\rightarrow} \mathrm{CaO}(\mathrm{~s})+\mathrm{CO}_2(\mathrm{~g}) $$
What is the mass of calcium carbonate required to produce 1.2 dm3 of carbon dioxide gas, CO2 at room conditions?
2. Zinc reacts with hydrochloric acid as follows:
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
What is the mass of zinc that should be used to produce 0.5 mol of hydrogen gas, H2?
3. A sample of iron(III) oxide, Fe2O3 is heated in a stream of excess hydrogen gas, H2 to produce 5.6 g of iron metal according to the following equation:
Fe2O3(g) + 3H2(g) → 2Fe(s) + 3H2O(l)
Calculate the mass of the iron(III) oxide sample.
4. Nitrogen and hydrogen gases react according to the following equation:
N2(g) + 3H2(g) → 2NH3(g)
How many molecules of ammonia, NH3 are produced if 6.72 dm3 of nitrogen gas at STP reacts completely with hydrogen gas?
Answer:
1. 5 g
2. 32.5 g
3. 8 g
4. 3.612 × 1023 ammonia molecules