Question

is a gas that forms close to the ground when air pollutants are heated by sunlight.

Explanation:

Analyze the question prompt

The question asks to identify a specific gas that forms close to the ground when air pollutants are heated by sunlight. This is a classic description of a secondary air pollutant formed via photochemical reactions.

Identify the chemical process

Using the Environmental Pollution knowledge point, we analyze the reaction. When primary pollutants like nitrogen oxides (\(\text{NO}_x\)) and volatile organic compounds (\(\text{VOCs}\)) react in the presence of sunlight and heat, they undergo photochemical reactions.

Determine the target gas

The primary harmful gas produced by these ground-level photochemical reactions is ozone (\(\text{O}_3\)), specifically referred to as ground-level ozone or tropospheric ozone. Unlike the protective ozone layer in the stratosphere, ground-level ozone is a major component of smog and a harmful air pollutant.

Answer:

<blank>Ozone</blank> is a gas that forms close to the ground when air pollutants are heated by sunlight.