Question

Examples of thermal decomposition reactions are:

1. \[\ce{2AgCl->2Ag + Cl2}\]
2. \[\ce{CaCO3->CaO + CO2}\]
3. \[\ce{2H2O->2H2 + O2}\]
4. \[\ce{2KClO3->2KCl + 3O2}\]

Options

• (i) and (ii)

• (ii) and (iii)

• (iii) and (iv)

• (ii) and (iv)

Answer 1

(ii) and (iv)

Explanation:

When a chemical is heated, it breaks down into simpler substances, a process known as thermal breakdown.

\[\ce{CaCO3 -> CaO + CO2}\]

When heated, calcium carbonate decomposes into calcium oxide and carbon dioxide in a thermal decomposition reaction.

\[\ce{2KClO3 -> 2KCl + 3O2}\]

In this additional thermal breakdown reaction, when potassium chlorate is heated, it breaks down into potassium chloride and oxygen gas.

On the other hand, reactions (i) and (iii) show electrolysis and photochemical breakdown.