Question

The weight percentage of a solution is $10$. Calculate the amount of solute to be added to $1$kg of the solution in order to saturate it. The solubility of the solute at that temperature is $25$.

• A. $100$g
• B. $25$g
• C. $125$g
• D. $225$g

Answer 1

The correct option is C

$125$g

Explanation of the correct option:
$\mathrm{Weight}\mathrm{percent}\mathrm{of}\mathrm{solution}=\frac{\mathrm{Weight}\mathrm{of}\mathrm{solute}}{\mathrm{Weight}\mathrm{of}\mathrm{solution}}\mathrm{x}100$

⇒$\mathrm{Weight}\mathrm{percent}\mathrm{of}\mathrm{solute}=\frac{\mathrm{Weight}\mathrm{percentage}\mathrm{of}\mathrm{solution}\mathrm{x}\mathrm{Weight}\mathrm{of}\mathrm{solution}}{100}$

⇒ $\mathrm{Weight}\mathrm{of}\mathrm{solute}=\frac{10\mathrm{x}1000\mathrm{g}}{100}$

⇒ $\mathrm{Weight}\mathrm{of}\mathrm{solute}=100\mathrm{g}$

Now, $\mathrm{Solubility}\mathrm{of}\mathrm{a}\mathrm{solute}=\frac{\mathrm{Amount}\mathrm{of}\mathrm{solute}\mathrm{in}\mathrm{saturated}\mathrm{solution}}{\mathrm{Amount}\mathrm{of}\mathrm{solvent}}\mathrm{x}100$

⇒$\mathrm{Amount}\mathrm{of}\mathrm{solute}\mathrm{in}\mathrm{saturated}\mathrm{solution}=\frac{\mathrm{Solubility}\mathrm{of}\mathrm{a}\mathrm{solute}\mathrm{x}\mathrm{Amount}\mathrm{of}\mathrm{solvent}}{100}$

⇒$\mathrm{Amount}\mathrm{of}\mathrm{solute}\mathrm{in}\mathrm{saturated}\mathrm{solution}=\frac{25\mathrm{x}900\mathrm{g}}{100}=225\mathrm{g}$

Now, to make the solution saturated we have to add $(225-100)\mathrm{g}=125\mathrm{g}$.

Hence, the correct option is (C).