Ncert Exercises & Solutions

1. Draw the gas phase and solid phase structure of H₂O₂.

2. H₂O₂ is a better oxidising agent than water. Explain.

(i) H₂O₂ has a non-planar structure. The molecular dimensions in the gas phase and solid phase are given below

(a) H₂O₂ structure in gas phase, dihedral angle is

111.5 °

(b) H₂O₂ strucutre in solid phase at 110 K, dihedral angle is

90.2 °

(ii) H₂O₂ is better oxidising agent than water as discussed below

(a) H₂O₂ oxidises an acidified solution of KI to give I₂ which gives blue colour with starch solution but H₂O does not.

2 KI + H_{2} {SO}_{4} + H_{2} O_{2}

K_{2} {SO}_{4} + 2 H_{2} O + I_{2}

(b) H₂O₂ turns black PbS to white PbSO₄ but H₂O does not

PdS + 4 H_{2} O_{2} \to {PbSO}_{4} + 4 H_{2} O