Question

calculate the mass of sodium sulphate required to prepare its 20÷( mass percent ) solution in 100g of water?

Answer 1

Mass of the solution = mass of solute + mass of solvent
Given that the mass percent of sodium sulphate solution is 20%.
Let the mass of sodium sulphate which is required to prepare this solution be x grams.
Given that the mass of water is 100 g.
So,
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
Thus, 25g of sodium sulphate is required.

Answer 2

$\red{\bf{\underline{\underline{Correct\:Question:}}} }$

$<b>Calculate the Mass of sodium sulphate required to prepare its 20%(mass percent) solution of 100g of water ? </b>$

$\green{\bf{\underline{\underline{SOLUTION:}}}}$

Let,

The mass of sodium sulphate required be = $xg$

The mass of sodium would be = $(x + 100)g$

$xg$ of solute in $(x + 100)g$ of solution,

$⟹{{20}={\dfrac{x}{x+100}}×100}$

$⟹{2x + 2000} = {100x}$

$⟹{80x} = {2000x}$

$⟹ {x=\dfrac{\cancel{2000}}{\cancel{80}}=\bf{25g}}$

Hence, to prepare 20% solution in 100 gram of water 25 gram of sodium sulphate is needed.