A solution of sodium sulphate is made in 100 g of water of mass by mass percentage 20. Calculate the mass of sodium sulphate in this solution.

Explanation

Suppose the mass of solute (sodium sulphate) = x g
The mass of solvent (water) = 100 g
`therefore` The mass of solution = (x + 100)g
`therefore` Mass percentage of solution
= `("Mass of solute")/("Mass of solution")xx100`
`20=x/((x+100))xx100`
`20(x+100)=100x`
`20x+2000=100x`
2000 = 100x - 20x
2000 = 80x
`2000/80=x`
25 = x
x = 25g
25 g of sodium sulphate would be added in the solution.