Q.How is acid rain formed? Explain its effect.

Step 1. Formation. Rain water normally has pH 5.6, from dissolved atmospheric CO₂. Burning fossil fuels (coal, oil) in power stations/furnaces, and petrol/diesel in motor engines, releases SO₂ and NO₂ into the air. These oxides are absorbed by the water droplets that make up clouds, and there react with oxygen and water:

When the resulting sulphuric acid and nitric acid push the rain's pH below 5.6, it is called acid rain.

Step 2. Effects (i). Acid rain causes extensive damage to buildings and marble structural materials, called Stone leprosy: $CaCO_3+H_2SO_4\rightarrow CaSO_4+H_2O+CO_2\uparrow$.

Step 3. Effects (ii)-(iii). It affects plant and animal life in aquatic ecosystems, and is harmful to agriculture, trees and plants, dissolving and removing nutrients needed for their growth. …

Cover both halves the question asks for -- the formation mechanism (with both balanced equations) and the fi …

• Giving only the SO₂/H₂SO₄ pathway and forgetting the parallel NO₂/HNO₃ pathway -- the unit names BOTH oxides as the main contr …