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WorksheetsEnvironmental Chemistry - Hardness in water
Total questions: 9
Worksheet time: 5mins
Complete the following sentence "Hard water is water that
forms a lather easily with water.
does not form a lather easily with water
Which of the following compounds are responsible for causing temporary hardness in water?
CaCl2
Ca(HCO3)2
CaSO4
Mg(HCO3)2
_________ hardness can be removed by boiling while __________ hardness cannot by removed by boiling.
(a)
Which of the following would be considered to be caused by temporary hardness in water?
Blocking of pipes with limescale
Furring of kettles
Scum formation when using soap
Coating of heating element of dishwasher, shower, washing machine with limescale
Which of the following are methods used to remove permanent hardness in water?
Distillation
Adding washing soda crystals
Boiling the water
Using an ion exchange resin
The removal of temporary hardness in water that is heated, is represented by which of the following equations?
H2O + CO2 ➡️ H2CO3
H2CO3 + CaCO3 ➡️ Ca(HCO3)2
Ca(HCO3)2 ➡️ CaCO3 + CO2 + H2O
When carbon dioxide reacts with water in the air, a weak acid called carbonic acid is produced. What is the formula of carbonic acid?
(a)
Carbonic acid falls as rainwater that is slightly acidic. This reacts with calcium carbonate, which is limestone rock, producing a soluble chemical that causes temporary hardness in water. What is the correct formula for this soluble compound?
(a)
When cold water containing temporary hardness is heated, an insoluble substance precipitates out of the water. What is the formula for this insoluble precipitate?
CaCO3
CaCO3
CO2
H2O
