Oxides of nitrogen formed in a car’s engine are removed using a catalytic converter.
What happens to the oxides of nitrogen in the catalytic converter?
A) They are hydrated.
B) They are neutralised.
C) They are oxidised.
D) They are reduced.
▶️ Answer/Explanation
Ans: D
In a catalytic converter, harmful nitrogen oxides (NOx) are reduced to nitrogen (N2) and oxygen (O2). This is a reduction reaction where the nitrogen gains electrons (its oxidation state decreases). The other options are incorrect because hydration (A) involves adding water, neutralization (B) involves acids and bases, and oxidation (C) would make the nitrogen oxides even more harmful.
Which row identifies two greenhouse gases and three processes by which they contribute to global warming?
▶️ Answer/Explanation
Ans: C
The two primary greenhouse gases are carbon dioxide (CO2) and methane (CH4). Oxygen (O2) is not a greenhouse gas. Greenhouse gases contribute to global warming through three main processes:
- Absorption of infrared radiation emitted by the Earth’s surface
- Emission of infrared radiation in all directions, including back toward the Earth’s surface
- Reflection of some of this thermal energy
The term “creation” of thermal energy is incorrect in this context, as greenhouse gases don’t create energy but rather trap and redistribute existing thermal energy. Therefore, option C is correct with the right combination of gases and accurate processes.
What are the approximate percentages of oxygen and nitrogen in clean, dry air?
▶️ Answer/Explanation
Ans: B
Clean, dry air is approximately 78% nitrogen and 21% oxygen by volume, with the remaining 1% being other gases like argon and carbon dioxide. Therefore, option B is correct. The other options either reverse the percentages (C, D) or provide incorrect values (A). These percentages are fundamental values in atmospheric chemistry.
Question
Which information about carbon dioxide and methane is correct?
Answer/Explanation
Ans:
B