Methane, , is often cited as a prototypical fuel that undergoes rapid combustion in…
CHEMISTRY · Multi-part · A Level · Chemistry · Oxidation, reduction and redox reactions · Oxidation, reduction and redox reactions
Problem
Methane, CH4, is often cited as a prototypical fuel that undergoes rapid combustion in air.
When one mole of gaseous methane reacts with excess oxygen at constant pressure and temperature, carbon is converted to carbon dioxide and elemental oxygen is reduced.
Answer the following questions about the reaction at the particulate and symbolic levels.
(a) Assign the oxidation numbers of carbon in CH4 and in CO2, and of oxygen in O2 and in CO2. Clearly indicate the direction of oxidation and reduction.
(b) Write the balanced chemical equation for the complete combustion of methane. State the total number of electrons transferred per mole of methane combusted, based on the oxidation-number changes you identified in part (a). Show your reasoning.
(c) Combustion is often classified as an oxidation–reduction process rather than an acid–base process. Using your results from parts (a) and (b), explain (i) why the reaction meets the criteria for a redox reaction and (ii) why it is not correctly described as an acid–base reaction under these conditions.