Magnesium ribbon burns in oxygen to form magnesium oxide.
2Mg(s)+O2(g)→2MgO(s) \mathrm{2Mg(s) + O_2(g) \rightarrow 2MgO(s)} 2Mg(s)+O2(g)→2MgO(s)During the reaction, each magnesium atom changes into a Mg2+\mathrm{Mg^{2+}}Mg2+ ion and each oxygen atom changes into an O2−\mathrm{O^{2-}}O2− ion.
State what happens to electrons when a species is:
oxidised
reduced
Complete the half equation by adding the number of electrons.
Mg→Mg2++___e− \mathrm{Mg \rightarrow Mg^{2+} + \_\_\_e^-} Mg→Mg2++___e−The electron transfers in the balanced reaction are summarised in the table.
| Particle | Number of particles reacting | Change for each particle |
|---|---|---|
| magnesium atom | 2 | loses 2 electrons |
| oxygen atom | 2 | gains 2 electrons |
Use the table to state:
(i) the total number of electrons lost by the magnesium atoms
(ii) the total number of electrons gained by the oxygen atoms
(iii) the species that is reduced
Magnesium can continue to burn in carbon dioxide.
2Mg+CO2→2MgO+C \mathrm{2Mg + CO_2 \rightarrow 2MgO + C} 2Mg+CO2→2MgO+C| Reactant | Change involving oxygen |
|---|---|
| magnesium | gains oxygen |
| carbon dioxide | loses oxygen |
State whether each reactant is oxidised or reduced.
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.