Question

Ravi has 20% (w/w) aqueous sugar solution which contains 5 g of sugar dissolved in it. The amount of water that he should evaporate in order to make its concentration 25% will be

Answer 1

Given info : Ravi has 20% (w/w) aqueous sugar solution which contains 5 g of sugar dissolved in it.

To find : the amount of water that should evaporate in order to make its concentration 25 % will be...

solution : case 1 : concentration of sugar = mass of sugar/mass of solution × 100

Let mass of water is x g

⇒20 = 5g/(5g + x g) × 100

⇒1 = 25/(x + 5)

⇒x = 20 g

case 2 : Now, let y g of water should be evaporated to make concentration of sugar is 25%

So, 25 = 5g/(20 - x + 5) × 100

⇒1 = 20/(25 - x)

⇒x = 5g

Therefore 5g of water should be evaporated to make conc of sugar is 25.