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What is Hard Water?
Hard water contains dissolved compounds, usually of
calcium or magnesium.
The compounds are dissolved when water comes into
contact with rocks.
Rainwater is naturally acidic and so it can dissolve minerals
that are in rocks to make a solution containing ions such
as Ca 2+, Mg 2+ and hydrogencarbonate HCO - and
3
Sulfate.…read more

Slide 3

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Hard water reacts Scum is formed by
with soap to precipitation of insoluble
form scum and metal salts of these acids:
so more soap is
needed to form Stearate ions+calcium ions
lather. calcium stearate
Soap is the sodium A lather forms only after the
salt of long chain soap has reacted with the
organic acids, for
example, sodium
metal ions in the water
stearate, C 17
H
COONa 35
Soft water readily forms a lather
with soap-there are few
dissolved ions to react with the
soap.…read more

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Soapless detergents do not Permanent and Temporary hardness
-Permanent hard water remains hard when its
form scum-there are no boiled.
stearate ions with Temporary hard water hard water is softened
dissolved metal ions. by boiling.
Permanent hard water is caused by rainwater
rainwater dissolving the sparingly soluble rock
gypsum, which is calcium sulfate.
Benefits of Hard Water Drawbacks of Hard Water
· Calcium compounds are good for · increase costs- more soap is needed
the development and maintenance of ·Produces scale that reduces the
bones and teeth and also help to efficiency of heating systems and
reduce heart disease. kettles.…read more

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Questions
What is hard water?
How is scum formed?
Which type of hard water can be softened by
boiling?
Explain how boiling hard water softens it
What are the advantages and disadvantages of
living in a hard water area?…read more

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