Question

Calculate the mass of sodium sulphate required to prepare it's 20% solution in 100g of water.

Answer 1

concentration of a solution = weight of solute / weight of solution multiplied 100

So, x /(x +100g) x 100 = 20%

therefore, x = 25g of sodium sulphate

Answer 2

• Given that the mass of water is 100 g.
• Let the mass of sodium be x

20 = [x/(x + 100)] * 100

20/100 = [x/x + 100]

1/5 = x/x + 100

x + 100/5 = x

x + 100 = 5x

5x - x = 100

4x = 100

x = 100/4

x = 25

25g of sodium sulphate is required.