Question

what happens when aqueous solution of sodium sulphate and barium chloride are mixed​

Answer 1

When an aqueous solution of sodium sulphate reacts with an aqueous solution of barium chloride, precipitate of barium sulphate is formed and following reaction takes place
Na2SO4 + BaCl2 ->BaSO4 + 2NaCl

Answer 2

When aqueous solution of sodium sulphate and barium chloride is mixed then then white precipitate of barium sulphate is formed along with the formation of sodium chloride.

i.e.,

BaCl2 + Na2SO4—–> BaSO4 + 2NaCl