JAMB Chemistry 2012 Question 14

Question 14

Water

The chemicals used to soften hard water involves the addition of

A.insoluble sodium compounds which form soluble solutions of calcium and magnesium
B.soluble sodium compounds which form soluble solutions of calcium and magnesium ions
C.soluble sodium compounds which form insoluble precipitates of calcium and magnesium ions
D.insoluble precipitates of calcium and magnesium ions.

Show the answer and explanation

Answer: C (soluble sodium compounds which form insoluble precipitates of calcium and magnesium ions)

Explanation

Washing soda (soluble Na₂CO₃) removes Ca²⁺ and Mg²⁺ as insoluble trioxocarbonates(IV).