A student adds magnesium powder to blue copper sulfate solution. The mixture gets warm, the blue colour fades and a pink-brown solid forms.
The ionic equation for the reaction is:
Mg(s)+Cu2+(aq)→Mg2+(aq)+Cu(s) \mathrm{Mg(s) + Cu^{2+}(aq) \rightarrow Mg^{2+}(aq) + Cu(s)} Mg(s)+Cu2+(aq)→Mg2+(aq)+Cu(s)Explain, in terms of electrons, which species is oxidised and which species is reduced.
Write the half equation for the reduction of the copper ions.
Sulfate ions are present in the solution but are not shown in the ionic equation.
Explain why.
Magnesium also reacts with copper oxide when the mixture is heated.
Mg+CuO→MgO+Cu \mathrm{Mg + CuO \rightarrow MgO + Cu} Mg+CuO→MgO+CuUse ideas about oxygen to explain why this is a redox reaction.
Copper oxide contains Cu²⁺ and O²⁻ ions. Magnesium oxide contains Mg²⁺ and O²⁻ ions.
Explain, in terms of electrons, why the reaction of magnesium with copper oxide is also a redox reaction.
112 exam-style questions on OCR GCSE Chemistry 3.3 Types of chemical reactions, covering 3.3.1 Oxidation and reduction in terms of oxygen, 3.3.2 Acids, alkalis and neutralisation, 3.3.3 The pH scale and measuring pH, 3.3.4 Oxidation and reduction in terms of electrons, 3.3.5 Dilute and concentrated, weak and strong acids, and 3.3.6 Hydrogen ion concentration and pH. Each one has a worked solution and a mark scheme showing where the marks go.