A student adds pieces of magnesium ribbon to 50 cm3\mathrm{cm^{3}}cm3 of dilute hydrochloric acid. The reaction produces hydrogen gas.
Mg(s)+2HCl(aq)→MgCl2(aq)+H2(g)\mathrm{Mg(s)} + 2\mathrm{HCl(aq)} \rightarrow \mathrm{MgCl_{2}(aq)} + \mathrm{H_{2}(g)}Mg(s)+2HCl(aq)→MgCl2(aq)+H2(g)
Relative atomic masses: H = 1, Mg = 24
At the end of one experiment some magnesium ribbon is left over. State which reactant is the limiting reactant.
Explain what is meant by the term limiting reactant.
In another experiment the student uses 0.60 g of magnesium with excess acid. Calculate the mass of hydrogen produced.
The student repeats the experiment with different masses of magnesium and the same volume and concentration of acid each time. The table shows the results.
| Mass of magnesium / g | Mass of hydrogen produced / g |
|---|---|
| 0.06 | 0.005 |
| 0.12 | 0.010 |
| 0.18 | 0.015 |
| 0.24 | 0.015 |
| 0.30 | 0.015 |
Describe the pattern shown for masses of magnesium from 0.06 g to 0.18 g.
Explain why the mass of hydrogen produced does not increase when more than 0.18 g of magnesium is used.
142 exam-style questions on Edexcel GCSE Chemistry 2.6 Calculations involving masses, covering 2.6.1 Relative formula mass and percentage composition, 2.6.2 Empirical and molecular formulae, 2.6.3 Conservation of mass, 2.6.4 Reacting masses and concentration in g dm⁻³, 2.6.5 The mole and the Avogadro constant, and 2.6.6 Limiting reactants and stoichiometry. Each one has a worked solution and a mark scheme showing where the marks go.