Question

(i) write reactions showing:

(a) Oxidation of Fe²⁺ ions into Fe³⁺ by hydrogen peroxide in acidic medium.

(b) Oxidation of KMnO₄ into MnO₂ by hydrogen peroxide in basic medium.

(ii) Find the volume strength of 1.6 N H₂O₂ solution?

(iii) Give one use of heavy water.

Answer 1

(i) (a) 2Fe²⁺(aq) + H₂O₂ (aq) + 2H⁺ → 2Fe³⁺(aq) + 2H₂O(l)

(b) 2KMnO₄ (aq) + 3H₂O₂ (aq) → 2MnO₂ (s) + 2KOH(aq) + 3O₂ + 2H₂O(l)

(ii) Strength of 1.6 NH₂O₂ solution

= 1.6 x 17 gL^-1

Now 68 g of H₂O₂ gives 22400 ml O₂ at STP

\(\therefore\) 1.6 × 17g of H₂O₂ will give

= \(\frac{22400}{68}\) x 1.6 x 17

= 8960 ml of O₂ at STP

But 1.6 × 17 g of H₂O₂ are present in 1000 ml of H₂O₂ solution 

Hence 1000 ml of H₂O₂ will give = 8.97 ml of O₂ at STP 

Hence the volume strength of 1.6 N H₂O₂ solution is 

= 8.96 Volume

or

Alternative method:

Apply formula

Volume strength = 5.6 × Normality

= 5.6 × 1.6

= 8.96

(c) Heavy water (D₂O) is extensively used as a moderator in nuclear reactors.