Question

calculate the mass of sodium sulphate required to prepare its 20% ( mass percent ) solution in hundred gram of water?

Answer 1

 the mass of sodium sulphate required be = x g 

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

x g of solute in (x + 100) g of solution 

20% = ×/x+100 x100 

20 x + 2000= 100 x 

80 x = 2000 

x = 2000/ 80 

= 25 g

Answer 2

If you mean 20% w/w, then: 
xg/(100 g + xg) = 20g/100g 
2000 + 20x = 100x 
x = 25 grams of sodium sulphate added to 100 g water 
This should give 25 grams in 125 grams of solution 
25/125 = 20%

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