Question

When 400 g of a 20 % solution by weight was cooled, 50 g of the solute precipitates. The percentage concentration of the remaining solution is ___.

• A. 8.57 %
• B. 15.32 %
• C. 12.25 %
• D. 9.51 %

Answer 1

The correct option is A 8.57 %

Weight of solute in solution = $400\times \frac{20}{100}=80$ g
Amount of solute remaining after precipitation = 80 – 50 = 30 g
Mass of solution remaining = 400 – 50 = 350 g
% concentration $=\frac{w_{\text{solute}}}{w_{\text{solution}}}\times 100=\frac{30}{350}\times 100=8.57\%$