In an acidic hydrogen-oxygen fuel cell, oxygen reacts at the positive electrode. O2+4H++4e−→2H2O\mathrm{O_{2} + 4H^{+} + 4e^{-} \rightarrow 2H_{2}O}O2+4H++4e−→2H2O Relative atomic mass: O = 16. Avogadro constant = 6.02 × 1023 per mole.
How many electrons are gained when 0.100 g of oxygen reacts?
1.88×10211.88\times10^{21}1.88×1021
3.76×10213.76\times10^{21}3.76×1021
7.53×10217.53\times10^{21}7.53×1021
1.51×10221.51\times10^{22}1.51×1022
42 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.