Investigation
Which ions cause hardness in water?
Aim: I want to find out what ions cause hardness in water and the reasons as to why certain ions have an effect and others don't.
Background information: Calcium hydrogen carbonate is the main cause of hard water. It forms when rain falls on rocks of limestone and chalk. These are made of calcium carbonate, which is not soluble in water. But rainwater contains carbon dioxide dissolved from the air, which makes it acidic. So it reacts with the rocks to form calcium hydrogen carbonate which is soluble and ends up in our taps. This reaction is:
H20(l) + C02(g) + CaC03 - Ca(HCO3)2(aq)
(Information taken from Complete Chemistry Book-Oxford University.)
Water that contains salts of calcium and magnesium principally as bicarbonates, chlorides, and sulphates. Ferrous iron may also be present; oxidized to the ferric form, it appears as a reddish brown stain on washed fabrics and enamelled surfaces. Water hardness that is caused by calcium bicarbonate is known as temporary, because boiling converts the bicarbonate to the insoluble carbonate; hardness from the other salts is called permanent. Calcium and magnesium ions in hard water react with the higher fatty acids of soap to form an insoluble gelatinous curd, thereby causing a waste of the soap. This objectionable reaction does not take place with modern detergents.
Which ions cause hardness in water?
Aim: I want to find out what ions cause hardness in water and the reasons as to why certain ions have an effect and others don't.
Background information: Calcium hydrogen carbonate is the main cause of hard water. It forms when rain falls on rocks of limestone and chalk. These are made of calcium carbonate, which is not soluble in water. But rainwater contains carbon dioxide dissolved from the air, which makes it acidic. So it reacts with the rocks to form calcium hydrogen carbonate which is soluble and ends up in our taps. This reaction is:
H20(l) + C02(g) + CaC03 - Ca(HCO3)2(aq)
(Information taken from Complete Chemistry Book-Oxford University.)
Water that contains salts of calcium and magnesium principally as bicarbonates, chlorides, and sulphates. Ferrous iron may also be present; oxidized to the ferric form, it appears as a reddish brown stain on washed fabrics and enamelled surfaces. Water hardness that is caused by calcium bicarbonate is known as temporary, because boiling converts the bicarbonate to the insoluble carbonate; hardness from the other salts is called permanent. Calcium and magnesium ions in hard water react with the higher fatty acids of soap to form an insoluble gelatinous curd, thereby causing a waste of the soap. This objectionable reaction does not take place with modern detergents.