When sodium reacts with oxygen, 0.20 mol of sodium (Na\text{Na}Na) reacts with 0.05 mol of oxygen gas (O2\text{O}_2O2).
Which is the correct balanced equation for the reaction?
Na+O2→NaO2\text{Na} + \text{O}_2 \rightarrow \text{NaO}_2Na+O2→NaO2
2Na+O2→Na2O22\text{Na} + \text{O}_2 \rightarrow \text{Na}_2\text{O}_22Na+O2→Na2O2
4Na+O2→2Na2O4\text{Na} + \text{O}_2 \rightarrow 2\text{Na}_2\text{O}4Na+O2→2Na2O
4Na+2O2→2Na2O24\text{Na} + 2\text{O}_2 \rightarrow 2\text{Na}_2\text{O}_24Na+2O2→2Na2O2
53 exam-style questions on AQA GCSE Chemistry 3.1 Chemical measurements, conservation of mass and the quantitative interpretation of chemical equations, covering 3.1.1 Conservation of mass and balanced chemical equations, 3.1.2 Relative formula mass, 3.1.3 Mass changes when a reactant or product is a gas, and 3.1.4 Chemical measurements. Each one has a worked solution and a mark scheme showing where the marks go.