UPSC Prelims 2010 · General Studies

Question 36: Science and Technology

Hydrogen fuel cell vehicles produce one of the following as “exhaust”

aNH₃

bCH₄

cH₂O

dH₂O₂

AnswerThe answer is (c).

A hydrogen fuel cell combines hydrogen with oxygen from the air in an electrochemical reaction that produces electricity, with water as the only product (2H2 + O2 gives 2H2O). The 'exhaust' of such a vehicle is therefore water vapour (H2O). No ammonia, methane or hydrogen peroxide is formed. Remember: fuel cell vehicles emit nothing but water at the tail pipe.

Why each option is right or wrong

(a) No ammonia is formed; only hydrogen and oxygen react.
(b) Methane contains carbon and the fuel has none.
(c) Right: the reaction produces water.
(d) Hydrogen peroxide is not the normal product of the cell reaction.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2010, General Studies, Series A. The paper on upsc.gov.in.