Question

Select from the following a decomposition reaction in which the source of energy for decomposition is light:

• A. 2FeSO4 → Fe2O3 + SO2 + SO3
• B. 2H2O → 2H2 + O2
• C. 2AgBr → 2Ag + Br2
• D. CaCO3 → CaO + CO2

Answer 1

Answer: (C)

2AgBr → 2Ag + Br2

Answer 2

Photolysis refers to a decomposition reaction driven by light energy. Silver bromide ($\text{AgBr}$) decomposes under light to form silver ($\text{Ag}$) and bromine ($\text{Br}_2$):

$2\text{AgBr} \rightarrow 2\text{Ag} + \text{Br}_2$

This reaction is extensively used in photographic films, where light exposure causes the breakdown of silver halides.