sblock Elements 1 Question 5
5. The strength of 11.2 volume solution of $\mathrm{H} _{2} \mathrm{O} _{2}$ is [Given that molar mass of
$\mathrm{H}=1 \mathrm{~g} \mathrm{~mol}^{-1}$ and $\mathrm{O}=16 \mathrm{~g} \mathrm{~mol}^{-1}$ ]
(a) $1.7 $%
(b) $34 $%
(c) $13.6 $%
(d) $3.4 $%
(2019 Main, 8 April II)
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Answer:
Correct Answer: 5. (d)
Solution:
- 11.2 volume of $\mathrm{H}_2 \mathrm{O}_2$ means that $1 \mathrm{~mL}$ of this $\mathrm{H}_2 \mathrm{O}_2$ will give $11.2 \mathrm{~mL}$ of oxygen at STP. $$ \begin{array}{ccc} 2 \mathrm{H}_2 \mathrm{O}_2(l) & \mathrm{O}_2(g) \ 234 \mathrm{~g} & 22.4 \mathrm{~L} \text { at STP } \end{array} \quad 2 \mathrm{H}_2 \mathrm{O}(l) $$
$22.4 \mathrm{~L}$ of $\mathrm{O}_2$ at STP is produced from $\mathrm{H}_2 \mathrm{O}_2 \quad 68 \mathrm{~g}$
$11.2 \mathrm{~L}_2$ of $\mathrm{O}_2$ at STP is produced from $$ \begin{array}{llll} \mathrm{H}_2 \mathrm{O}_2 & \frac{68}{22.4} & 11.2 \quad 34 \mathrm{~g} \end{array} $$
$34 \mathrm{~g}$ of $\mathrm{H}_2 \mathrm{O}_2$ is present in $1000 \mathrm{~g}$ of solution
%$w / w \quad \frac{34}{1000} \times 100 = 3.4 $%
