AQA Chemistry Hardness of Water

  • Created by: Benjamin
  • Created on: 01-04-13 16:51
Wich two substances does hard water form?
Scum and scale
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How does the time it takes for a quality lather to form in hard water differ for the time it takes to form in soft water from an ordinary bar of soap
Hard water: A long time , Soft water: Very fast
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Name the ions that are present in hard water
Calcium and Magnesium
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When calcuim and magnesium react with soap wich insoluble substance do they form?
Scum
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When hard water is heated, what does it form, and what is this substance mainly made up of?
Sale, mostly calcium carbonate
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Explain why kettle heating elements with a build up of scale are not very efficient
Scale is a thermal insulator, Kettle takes longer to boil, becomes less effiecent
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What charges are present on the Calcium and Magnesium Ions
2+
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Watch a video on rain falling onto limestone, chalk... and how this makes the water hard
:)
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Give two advantages of hard water for your health
Ca 2+ Ions are good for maintaining healthy bones and teeth, Reduced the risk of heart disease
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In simple mans terms, how do we make hard water soft?
By removing the Calcium and Magnesium Ions
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State the two types of hardness
Temporary and permenant
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What is temporary hardness caused by?
The Hydrogencarbonate ion, HCO3 (-1 charge) in Ca(HCO3)2
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What is permenant hardness caused by?
Dissolved calcium sulfate
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By which process can temporary hardness be removed?
By boiling
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What happens to the calcium hydrocarbonate in temporary hard water when we boil it?
It decomposes to form calcium carbonate
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Is calcium carbonate soluble? Thus how does it effect the efficiency of kettles
It is insoluble. It isn't a conductor of heat energy so it takes longer for a kettles heating element to transfer heat energy to the water.
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Both temporary and permanent hardness can be softened. How is this done?
By adding washing soda (sodium carbonate)/ Running water through an ion exchange resin
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What is the formula for washing soda (sodium carbonate)?
Na2CO3
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When the carbonate ions in washing soda react with the calcium and magnesium ions in the hard water, what is formed?
An insoluble precipitate of calcium carbonate and magnesium carbonate.
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Watch a video on the effects of running water through an ion exchange resin
:)
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When Calcium carbonate reacts with a weak acidic solution (rain water, streams) what does it form?
Calcium hydrogencarbonate
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Other cards in this set

Card 2

Front

How does the time it takes for a quality lather to form in hard water differ for the time it takes to form in soft water from an ordinary bar of soap

Back

Hard water: A long time , Soft water: Very fast

Card 3

Front

Name the ions that are present in hard water

Back

Preview of the front of card 3

Card 4

Front

When calcuim and magnesium react with soap wich insoluble substance do they form?

Back

Preview of the front of card 4

Card 5

Front

When hard water is heated, what does it form, and what is this substance mainly made up of?

Back

Preview of the front of card 5
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