CAIE A-Level Chemistry 12.1.5 NOx in Acid Rain Formation

Practise equations for direct nitric-acid formation and the catalytic role of NO and NO2 in oxidising atmospheric SO2.

Exam points

write a balanced equation showing NO2 reacting with water, and oxygen where required, to form nitric acid
explain the NO/NO2 catalytic cycle that oxidises atmospheric SO2 to SO3
complete the sulfuric-acid pathway by reacting SO3 with atmospheric water

[Maximum number: 1]

Nitrogen and phosphorus are elements in Group 15 of the Periodic Table.

Nitrogen is found in inorganic compounds such as nitrogen oxides ( $\mathrm{NO}_{x}$ ), nitrates and nitric acid.

Write an equation to describe the role of $\mathrm{NO}_{2}$ in the direct formation of acid rain.

$2 \mathrm{NO}_{2}+\mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{HNO}_{2}+\mathrm{HNO}_{3} \mathrm{OR} 4 \mathrm{NO}_{2}+\mathrm{O}_{2}+2 \mathrm{H}_{2} \mathrm{O} \rightarrow 4 \mathrm{HNO}_{3}$

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12.1.5—Role of NO and NO2 in the formation of acid question 1