Question

Pehal and Ishaan we're making 100g sugar solutions with concentration by mass 20% and 50% respectively.Pehal added 20g of sugar in her solution whereas Ishaan evaporated 20g of water from his solution. Now the two solutions were mixed to form a final solution. The concentration by mass of final solution is

A) 28%
B)45%
C)40%
D)60%

Answer 1

20% by mass sugar solution means 20 g of the sugar is dissolved in 100g of solution or 80 g of water. 50 % by mass sugar solution means 50g of the sugar is dissolved in 100g of solution or 50 g of water.
Total mass of sugar is (20+20)+ 50= 90g
Total mass of water is 80g +(50-20)= 110g
Total mass of solution = 90+110 = 200g
The concentration by mass of final solution is : 90g/200g * 100 = 45%
so 45% is the answer