Which equation is correctly balanced?
H2+O2→H2O\mathrm{H_{2}} + \mathrm{O_{2}} \rightarrow \mathrm{H_{2}O}H2+O2→H2O
2H2+2O2→2H2O2\mathrm{H_{2}} + 2\mathrm{O_{2}} \rightarrow 2\mathrm{H_{2}O}2H2+2O2→2H2O
2H2+O2→2H2O2\mathrm{H_{2}} + \mathrm{O_{2}} \rightarrow 2\mathrm{H_{2}O}2H2+O2→2H2O
H2+2O2→H2O\mathrm{H_{2}} + 2\mathrm{O_{2}} \rightarrow \mathrm{H_{2}O}H2+2O2→H2O
230 exam-style questions on Edexcel GCSE Chemistry 1.1 Formulae, equations and hazards, covering 1.1.1 Formulae, word and balanced equations, 1.1.2 Balanced ionic equations, and 1.1.3 Hazard symbols and risk in practical work. Each one has a worked solution and a mark scheme showing where the marks go.