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JAMB Chemistry 2002 Question 22

Question 22

Water

The furring of kettles is caused by the presence in water of

  1. A.calcium tetraoxosulphate (VI)
  2. B.calcium hydrogentrioxocarbonate (IV)
  3. C.calcium hydroxide
  4. D.calcium trioxocarbonate (IV).
Show the answer and explanation

Answer: B (calcium hydrogentrioxocarbonate (IV))

Explanation

Temporary hard water contains dissolved Ca(HCO3)2. On boiling it decomposes: Ca(HCO3)2 → CaCO3 + H2O + CO2, and the insoluble CaCO3 forms the fur.