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JAMB Chemistry 2007 Question 45

Question 45

Water

When temporary hard water is boiled for some time in a kettle, the inner surface of the kettle becomes coated with a deposit of

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

Answer: B (calcium trioxocarbonate(IV))

Explanation

Boiling decomposes dissolved Ca(HCO3)2 into insoluble CaCO3, CO2 and water; the CaCO3 forms the fur in the kettle.