Why does the hardness of water render it unfit for use in a

(i) boiler

(ii) for washing purposes?

(i) The dissolved substance present in the hard water does not convert into steam and gets deposited on the inner walls of the tube. Hence, the tubes become narrower and eventually less steam is produced.

When bore of the tube becomes very narrow, the pressure of steam increases so much that at times the boiler itself bursts. Hence, hard water is unfit for use in boilers.

(ii) If the water is hard, calcium and magnesium ions of the water combine with the negative ions of the soap to form a slimy precipitate of insoluble calcium and magnesium usually called soap curd (scum).

Formation of soap curd will go on as long as calcium and magnesium ions are present. Till then, no soap lather will be formed and cleaning of clothes or body will not be possible. Moreover, these precipitates are difficult to wash from fabrics and sometimes form rusty spots if iron salts are present in water.