Question

Consider the following statements:
Hard water does not give lather with soap because hard water contains:
(a) calcium bicarbonate
(b) magnesium bicarbonate
(c) chlorides of calcium and magnesium
(d) sulphates of calcium and magnesium
Which of these statements are correct?

• A. (a) and (b)
• B. (c) and (d)
• C. (a), (b) and (c)
• D. (a), (b), (c) and (d)

Answer 1

Answer: (B)

(c) and (d)

Since, hard water contains soluble chloride and sulphate salts of calcium and magnesium which forms insoluble curdy precipitate.
$\underset{solublesodiumstearate\left(soap\right)}{2C_{17}{H}_{35}COONa}+\underset{calciumchloride\left(inhardwater\right)}{CaC{l}_2}⟶\underset{insolublecalciumstearate}{{\left(C_{17}{H}_{35}COO\right)}_{2}Ca}+2NaCl$
$\underset{solublesodiumstearate}{2C_{17}{H}_{35}COONa}+\underset{Magnesiumsulphate\left(inhardwater\right)}{MgS{O}_4}⟶\underset{Insolublemagnesiumstearate\left(soap\right)}{{\left(C_{17}{H}_{35}COO\right)}_{2}Mg}+{Na}_{2}S{O}_4$