10 g of a mixture of barium chloride and anhydrous sodium sulphate is dissolved in water. An excess of barium chloride solution is added and 6.99 g of barium sulphate is precipitated according to the equation given below:
Na2SO4 + BaCl2 → BaSO4 +2NaCl
[O = 16, Na = 23, S = 32, Ba = 137]
Calculate the percentage of sodium sulphate in the original mixture.
42.6 %