Question

5.34g of salt of formula M2SO4 were dissolved in water the sulphate ion was precipitated by adding excess barium chloride solution during which 4.66 barium sulphate were obtained. How many moles of M2SO4 were in the solution?

Answer 1

BaSO4 precipitates 1:1 with SO4^2-, so moles M2SO4 = moles BaSO4.

M(BaSO4) ≈ 137.33 + 32.06 + 4×16.00 = 233.39 g·mol^-1

moles = 4.66 g / 233.39 g·mol^-1 ≈ 0.020.

So 2.0×10^-2 mol of M2SO4 were present.