Question

A mixture of $2g$ of sodium sulphate and $100 \, m$ mol of $Ca\left(\right. O H \left.\right)_{2}$ was dissolved in water and the volume was made up to $100 \, mL.$ What are the mass of calcium sulphate formed and the concentration of $OH^{-}$ in resulting solution, respectively?
Given:- (Molar mass of $Ca\left(O H\right)_{2}, \, Na_{2}SO_{4}$ and $CaSO_{4}$ are $74, \, 143 \, $ and $ \, 136g \, mol^{- 1},$ respectively; $K_{s p}$ of $Ca\left(O H\right)_{2}is \, 5.5\times \left(10\right)^{- 6}$ )

• A. $1.9 \, g, \, 0.14 \, mol \, L^{- 1}$
• B. $13.6 \, g, \, 0.28 \, mol \, L^{- 1}$
• C. $1.9 \, g, \, 0.28 \, mol \, L^{- 1}$
• D. $13.6 \, g, \, 0.14 \, mol \, L^{- 1}$

Answer 1

Answer: (C)

Mass of $CaSO_{4}=\frac{14 \times 136}{1000}=1.9 \, g$
$CaSO_{4}=\frac{14 \times 136}{1000}=1.9 \, g$
$\left[O H^{-}\right]=\frac{28}{100}=0.28 \, M$