Hydrogen can be made by three routes. (Relative atomic masses: H = 1, C = 12, O = 16)
Route 1: CH4+2H2O→CO2+4H2\mathrm{CH_{4} + 2H_{2}O \rightarrow CO_{2} + 4H_{2}}CH4+2H2O→CO2+4H2
Route 2: 2H2O→2H2+O2\mathrm{2H_{2}O \rightarrow 2H_{2} + O_{2}}2H2O→2H2+O2
Route 3: C+H2O→CO+H2\mathrm{C + H_{2}O \rightarrow CO + H_{2}}C+H2O→CO+H2
Which shows the routes in order of atom economy for hydrogen, highest first?
Route 3, Route 2, Route 1
Route 2, Route 1, Route 3
Route 2, Route 3, Route 1
Route 1, Route 2, Route 3
157 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.