A harbour uses a hydrogen/oxygen fuel cell to provide electricity for equipment on the quayside. It is choosing between two hydrogen producers.
Producer A makes hydrogen by electrolysis of water using electricity from the national grid.
Producer B makes hydrogen from natural gas.
Both supplies would be used in the same fuel cell.
A harbour officer says:
"Producer A's hydrogen has lower overall carbon dioxide emissions because water, rather than natural gas, is used to make it."
Which is the best evaluation of this claim?
The claim cannot be confirmed because grid electricity may come from burning fossil fuels, so emissions from both production routes need comparing.
The claim is reasonable because water contains no carbon, so the electrolysis route should have no carbon dioxide emissions.
The claim is reasonable because emissions from generating electricity should not be included when assessing the hydrogen-production route.
The claim may be correct, but only because Producer A's hydrogen would release less carbon dioxide when it reacts in the fuel cell.
131 exam-style questions on OCR GCSE Chemistry 6.2 Organic chemistry, covering 6.2.1 Crude oil and fractional distillation, 6.2.2 Cracking and dependence on hydrocarbons, 6.2.3 Functional groups and homologous series, 6.2.4 Reactions of alkanes, alkenes and alcohols, 6.2.5 Addition polymerisation and repeat units, 6.2.6 Naturally occurring polymers, 6.2.7 Chemical cells and fuel cells, and 6.2.8 Condensation polymerisation and how to make one. Each one has a worked solution and a mark scheme showing where the marks go.