A mixture of 100 mmol of Ca(OH)2 and 2 g of sodium
sulphate was dissolved in water and the volume was
made up to 100 mL. The mass of calcium sulphate
formed and the concentration of OH– in resulting
the solution, respectively, are (Molar mass of Ca(OH)2,
Na2SO4 and CaSO4 are 74, 143 and 136 g mol–1,
respectively; Ksp of Ca(OH)2 is 5.5 × 10–6)Na2SO4 + Ca(OH)2 → CaSO4 + 2 NaOH
mmol of Na2SO4 = 2*1000/143
=13.98 m Mol
mmol of CaSO4 formed = 13.98 m Mol
Mass of CaSO4 formed = 13.98 × 10^-3 × 136 = 1.90 g
mmol of NaOH = 28 mmol
Ca(OH)2 → Ca2+ + 2 OH-
[OH–] = 28 mmol / 100ml=0.028 mol/0.1 L =0.28mol L-1
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