Question

Half litre each of three samples of $H_2{O}_2$ labelled $10$ volume, $15$ volume and $20$ volume are mixed and then diluted with equal volume of water. The relative strength of resultant $H_2{O}_2$ solution is:

• A. $2.5$
• B. $5.0$
• C. $7.5$
• D. $10$

Answer 1

The correct option is C $7.5$

Volume strength of $H_2{O}_2=5.6\times \text{N}$ $(\text{N}=$ Normality$)$

Normality of $10$ vol of $H_2{O}_2=\frac{10}{5.6}\text{N}$

Normality of $15$ vol of $H_2{O}_2=\frac{15}{5.6}\text{N}$

Normality of $20$ vol of $H_2{O}_2=\frac{20}{5.6}\text{N}$

Let $500$ ml of each is mixed, then the total volume of mix $=1500$ ml.

Also, this is diluted to double its volume, i.e., $=3000$ ml

$\text{N}\times 3000$ = $\frac{10}{5.6}\times 500+\frac{15}{5.6}\times 500+\frac{20}{5.6}\times 500$

Normality of $H_2{O}_2$ mix $=1.339\text{N}$

Vol. strength of $H_2{O}_2=1.339\times 5.6=7.5$.