When excess lead nitrate solution was added to a solution of sodium sulphate, 15.15 g of lead sulphate were precipitated.
What mass of sodium sulphate was present in the original solution?
Na2SO4 + Pb(NO3)2 → PbSO4 + 2NaNO3
[Na = 23, S = 32, O = 16, Pb = 207, N = 14]