JAMB Chemistry 2007 Objective — Question 12

Question 12 of 50 from the Joint Admissions and Matriculation Board (JAMB) Chemistry 2007 Objective paper, with the correct answer and a full explanation.

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

A. calcium trioxocarbonate(IV)Correct
B. calcium tetraoxosulphate (VI)
C. aluminium trioxocarbonate(IV)
D. calcium hydrogen trioxocarbonate (IV)

Explanation

Boiling decomposes calcium hydrogencarbonate, Ca(HCO3)2 -> CaCO3 + H2O + CO2, depositing insoluble calcium trioxocarbonate(IV) (limescale).

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