Air Pollution

Step 1: Understanding the Concept:
Acid rain is precipitation that is unusually acidic. It is caused when certain precursor gases are released into the atmosphere, where they react with water, oxygen, and other chemicals to form acidic compounds.

Step 3: Detailed Explanation:
The two primary precursor gases responsible for acid rain are:
While CO does form carbonic acid and makes normal rain slightly acidic (pH ~5.6), it is not considered the cause of the "acid rain" problem, which refers to rain with a much lower pH. O (ozone) is an oxidant that can facilitate the formation of acids but is not a precursor itself. NH (ammonia) is a basic gas.

Step 4: Final Answer:
The primary acid-forming precursor gases that cause acid rain are NO and SO .

Step 1: Understanding the Concept:
The question asks to identify a primary air pollutant from the given options. Primary pollutants are substances directly emitted into the atmosphere from a source (e.g., from a factory chimney or a volcanic eruption). Secondary pollutants are not directly emitted but form in the atmosphere when primary pollutants react with each other or with other atmospheric components.

Step 3: Detailed Explanation:

Step 4: Final Answer:
Ash from a volcanic eruption is a primary air pollutant.