Question

Kamal prepared 300 g of 20% (w/w) aqueous solution of common salt. Teacher asked him to make the concentration of solution 5% (w/w). Calculate the amount of water that should be added to the solution and choose the correct option.​

Answer 1

Answer:

900g

Explanation:

x÷300×100=60

x=60

now,

adding y to make concentration 5 percent

60÷300+y×100=5

60÷300+y=5÷100

300+y÷60=100÷5

300+y=1200

y=1200-300

y=900g

Answer 2

Given info : Kamal prepared 300 g of 20% (w/w) aqueous solution of common salt. Teacher asked him to make the concentration of solution 5% (w/w).

To find : the amount of water that should be added to the solution is ...

solution : Kamal prepared 300g of 20% (w/W) aqueous solution of common salt.

now the mass of common salt = 20 % of 300g = 60g

now the teacher asked him to make the concentration of solution is 5 %.

it means, he should dilute the solution by adding water.

let x g amount of water to the solution.

after adding, mass of solution = (300 + x) g

but the mass of common salt remains constant and that is 60 g

now the percentage of common salt in the solution = 5 % [given]

⇒ mass of common salt/mass of solution × 100 = 5

⇒ 60/(300 + x) = 1/20

⇒ 1200 = 300 + x

⇒ x = 900 g

therefore 900g of water should be added to the solution to make it 5% (w/W).