An emergency oxygen generator contains potassium chlorate, which decomposes when heated.
2KClO3(s)→2KCl(s)+3O2(g)\mathrm{2KClO_{3}(s) \rightarrow 2KCl(s) + 3O_{2}(g)}2KClO3(s)→2KCl(s)+3O2(g)
One mole of any gas occupies 24 dm324\,\mathrm{dm^{3}}24dm3 at room temperature and pressure.
Relative formula mass: KClO3=122.5\mathrm{KClO_{3}} = 122.5KClO3=122.5
Calculate the volume of oxygen produced at room temperature and pressure when 49.0 g of potassium chlorate decomposes completely.
In a laboratory test, all the oxygen produced in (a) is transferred to a vessel containing 11.2 g of iron. The iron reacts completely.
4Fe(s)+3O2(g)→2Fe2O3(s)\mathrm{4Fe(s) + 3O_{2}(g) \rightarrow 2Fe_{2}O_{3}(s)}4Fe(s)+3O2(g)→2Fe2O3(s)
Relative atomic mass: Fe=56\mathrm{Fe} = 56Fe=56
Calculate the volume of oxygen remaining at room temperature and pressure.
In a separate high-temperature process, an unknown mixture containing only ammonia and oxygen is allowed to react.
4NH3(g)+5O2(g)→4NO(g)+6H2O(g)\mathrm{4NH_{3}(g) + 5O_{2}(g) \rightarrow 4NO(g) + 6H_{2}O(g)}4NH3(g)+5O2(g)→4NO(g)+6H2O(g)
The reaction continues until one reactant has been completely used. The temperature and pressure remain constant. Measurements of two gases present at the end are shown in the table.
| Gas | Volume / cm3\mathrm{cm^{3}}cm3 |
|---|---|
| oxygen | 18 |
| nitrogen monoxide | 72 |
Determine the initial volume of each reactant. Explain, using the calculated volumes, which reactant was in excess.
151 exam-style questions on Edexcel GCSE Chemistry 6.2 Quantitative analysis, covering 6.2.1 Concentration in mol dm⁻³ and titration calculations, 6.2.2 Percentage yield and why actual yield falls short, 6.2.3 Atom economy of a reaction, 6.2.4 Choosing a reaction pathway, and 6.2.5 Molar volume of gases and Avogadro's law. Each one has a worked solution and a mark scheme showing where the marks go.