Direct methanol fuel cells are being developed to power portable electronic devices. Methanol, CH3OH\mathrm{CH_{3}OH}CH3OH, is a liquid at room temperature. In the cell, methanol reacts with oxygen to form carbon dioxide and water.
The table shows some bond energies.
| Bond | Bond energy / kJ mol−1\mathrm{kJ\,mol^{-1}}kJmol−1 |
|---|---|
| H–H | 436 |
| O=O | 498 |
| O–H | 464 |
Balance the equation for the overall reaction in the methanol fuel cell: ...... CH3OH+\mathrm{CH_{3}OH} +CH3OH+ ...... O2→\mathrm{O_{2}} \rightarrowO2→ ...... CO2+\mathrm{CO_{2}} +CO2+ ...... H2O\mathrm{H_{2}O}H2O
A hydrogen-oxygen fuel cell uses the reaction: 2H2(g)+O2(g)→2H2O(g)2\mathrm{H_{2}(g)} + \mathrm{O_{2}(g)} \rightarrow 2\mathrm{H_{2}O(g)}2H2(g)+O2(g)→2H2O(g). Calculate the energy change for this reaction using the bond energies.
Explain, using your answer to (b), whether the reaction is exothermic or endothermic.
Give one advantage and one disadvantage of a methanol fuel cell compared with a hydrogen-oxygen fuel cell for powering a laptop.
Calculate the volume of oxygen, in dm3\mathrm{dm^{3}}dm3, at room temperature and pressure, needed to react completely with 16 g of methanol in the fuel cell. Relative formula mass: CH3OH=32\mathrm{CH_{3}OH} = 32CH3OH=32. The volume of one mole of any gas at room temperature and pressure is 24 dm3\mathrm{dm^{3}}dm3.
38 exam-style questions on Edexcel GCSE Chemistry 6.4 Chemical cells and fuel cells, covering 6.4.1 Chemical cells and fuel cells. Each one has a worked solution and a mark scheme showing where the marks go.