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JAMB Chemistry 1997 Question 15

Question 15

Water

A major process involved in the softening of hard water is the

  1. A.conversion of a soluble calcium salt to its trioxocarbonate (IV)
  2. B.decomposition of calcium trioxocarbonate (IV)
  3. C.conversion of an insoluble calcium salt to its trioxocarbonate (IV)
  4. D.oxidation of calcium atoms to its ions.
Show the answer and explanation

Answer: A (conversion of a soluble calcium salt to its trioxocarbonate (IV))

Explanation

Hardness is caused by dissolved calcium salts. Softening (by boiling or adding washing soda) changes these soluble salts into insoluble calcium trioxocarbonate(IV), which settles out and removes Ca2+ from the water.