Question

10. Pehal and Ishaan were making 100 g sugar solutions with concentration by mass 20% and 50% respectively. Pehal added 20 g of sugar in her solution whereas Ishaan evaporated 20 g of water from his solution. Now, the two solutions were mixed to form a final solution. The concentration by mass of final solution is (1) 28% (3) 40% (2) 45% (4) 60%

Answer 1

Answer:The correct option (2).

Solution:

In Pehal 20% sugar solution , she added 20 g of sugar more.

Amount of sugar present = 20 grams

Amount of sugar added from outside in the solution= 20 grams

Amount of sugar after addition = 20+20=40 grams

Amount of water = 80 grams

$M_{pehal}$= Total mass of solution= 80+40= 120 grams

In Ishaan 50% sugar solution, he evaporated 20 g of water.

Amount of sugar present = 50 grams

Amount of water present= 50 grams

Amount of water evaporated= 20 grams

Amount of water after evaporation = 50 - 20 = 30 grams

$M_{ishan}$ = Total mass of solution=50 + 30= 80 grams

After mixing both the solution

Total amount of sugar after the mixing of solutions,(M) = 40+50 = 90 grams

Percentage of sugar after mixing=$\frac{\text{ Total mass of sugar after the mixing of solutions}\times 100}{M_{ishan}+M_{pahel}}$

$\frac{90\times 100}{200}=45\%$

Mass percentage of sugar in final solution= 45%