JAMB - Chemistry (2002 - No. 20)

The furring of kettles or boilers - this is as a result of the decomposition of \(Ca(HCO_3)_2\) into \(CaCO_3\), and this\(CaCO_3\) coats the inside of a kettle or boiler used in heating water containing dissolved \(Ca(HCO_3)_2\).

When a kettle has been used to boil temporary hard water for quite some time, the inner surfaces become coated with a white fur-like layer. This layer (furring of the kettle) is due to the gradual deposition of calcium trioxocarbonate(IV), from the decomposition of Calcium hydrogentrioxocarbonate (IV).