Sodium Sulphate

The concentration of bivalent lead ions in a sample of polluted of polluted water that aslo contains nitrate ions is determined by adding solid sodium sulphate (M=142) to exactly 500mL water. Calculate the molarity of lead ions if 0.355g is sodium sulphate was nedded for complete precipitation of lead ions as sulphate.

Glauberite is a mineral containing sodium sulphate (M= 142.0) and calcium-sulphate (M=136) only. It is the chief source of sodium sulphate, which is used in making glass. If a 20.00 g sample of glauberite contains 2.88 g of calcium (M = 40), what mass of sodium sulphate can be extracted from 1 ton (1000 kg) of glauberite?

Anhydrous sodium sulphate can absorb water vapour and convert to its decahydrate. By how many gram would the mass of a 1 g sample of the thoroughly dried sodium sulphate increase, if its is exposed to sufficient water vapour to be converted to the decahydrate.

If sodium sulphate is considered to be completely dissociated into cations and anions in aqueous solution , the change in freezing point of water (DeltaT_(f)) when 0.01 mole of sodium sulphate is dissociated in 1 kg of water is : ( K_(f) = 1.86 K kg mol^(-1) )