Q.Statues and monuments in India are affected by acid rain. How?

Statues and monuments made of marble or limestone are built of calcium carbonate (CaCO3). Acid rain — rain water made acidic (pH below the natural ~5.6) by dissolved SO2 and NOx from polluted air, which are oxidised and hydrated to form sulphuric acid (H2SO4) and nitric acid (HNO3) — attacks this calcium carbonate chemically.

CaCO3 reacts with the acids present in acid rain:

The calcium sulphate and calcium nitrate formed are water-soluble (unlike the original insoluble CaCO3), so they are gradually washed away or leached out by rain, and CO2 gas escapes. Repeated exposure over years dissolves away the surface of the marble, causing pitting, loss of fine carved detail, yellowing and a rough, corroded texture — a form of damage often referred to as 'marble cancer' or 'stone leprosy'. …

Identify that monuments are made of CaCO3, that acid rain contains H2SO4/HNO3, write the acid–carbonate reactions, and explain that the so …

• Forgetting to write/balance the actual chemical reaction between CaCO3 and the acids.
• Saying the acid simply 'dissolves' the marble without explaining that a new soluble salt is formed which is then washed away. …