hardness of water Flashcards
what is the hardness of water caused by?
ca2+ and mg2+ ions and rain falling on some rocks which dissolves to form the compound magnesium sulfate
ads of ca2+ ions?
- healthy for teeth and bones
- less risk of developing heart disease
what is temporary hard water caused by?
- caused by HCO-3 in Ca(HCO3)2
- removed by boiling
- when heated calcium hydrogencarbonate will decompose to become insoluble CaCO3
what does hard water form?
nasty scum unless you’re using soapless detergents
what do calcium ions and magnesium ions form?
scum (when added to soap) = insoluble
what happens when you heat hard water?
scale forms on insides of pipes, boilers and kettles which blocks pipes and reduces efficient of appliance
what is scale?
a thermal insulator
what does scale do?
it takes longer to boil as it is less efficient
what does distilled water contain?
little or no hardness
imported water is..
more hard than local water
what is local water?
it is temporarily hard, all hardness is removed by boiling
what is imported water?
temporary and hard (permanent)
what is permanent water caused by?
dissolved calcium sulfate
how are both softened?
by adding washing soda (Na2CO3)
what does adding a carbonate to calcium and magnesium ions form?
an insoluble precipitate of Ca carbonate and Mg carbonate
