Question

A storage battery contains a solution of $H_{2}S{O}_4$ 30% by weight. Find out Molarity?
(Given density of solution $=1.2g/c{m}^3$)

• A. 2.07 M
• B. 5.00 M
• C. 4.67 M
• D. 3.67 M

Answer 1

The correct option is D 3.67 M

Concentration of $H_{2}S{O}_4$ = 30% by weight
Weight percent is the weight in grams of the solute per 100 g of the solution.​
$\Rightarrow W_{\text{solute}}=30g{W}_{\text{solution}}=100g{W}_{\text{solvent}}=70g$

$\text{Density}=\frac{\text{Mass}}{\text{Volume}}$
Given,
Density of solution = $1.2g/c{m}^3$
Therefore,
$V_{\text{solution}}=\frac{100}{1.2}mL$

Molar mass of $H_{2}S{O}_4$ = 98 $gmo{l}^{-1}$
Molar mass of $H_{2}O$ = 18 $gmo{l}^{-1}$
$n_{\text{solute}}=\frac{30}{98}=0.306mol$

Molarity is the number of moles of solute present in 1 litre of the solution.

$\text{Molarity}=\frac{\text{Number of moles of solute}}{\text{Volume of solution in litre}}$

$\text{Molarity}=\frac{n_{\text{solute}}\times 1000}{V_{\text{solution}}}$

$\text{Molarity}=\frac{0.306\times 1000\times 1.2}{100}=3.67M$