The hardness of water

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  • Created by: jfawdon26
  • Created on: 12-03-16 15:59
What does soft water form with soap?
A lather
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What 2 things does hard water form with soap?
Scum and scale
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Is scum soluble or insoluble?
Insoluble
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When will scale form?
When hard water is heated
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Where is scale usually found?
Inside of kettles
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What kind of ions are found in hard water that make it hard?
Magnesium and calcium ions
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How does hard water become hard?
When the water runs off rocks such as limestone and chalk, it dissolves magnesium and calcium ions into the water
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True or false, hard water is said to reduce tooth decay when drank?
True
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What ion causes temporary hard water?
Hydrogencarbonate ions
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What causes permanent hard water to be permanent?
Dissolving calcium sulfate into it.
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How is temporary hardness removed from water?
By boiling the water. This causes the hydrogencarbonate to decompose to form calcium carbonate (limestone) which makes limescale. Once the hydrogencarbonate ions have been removed, it is no longer considered as hard water.
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What happens when sodium carbonate is added to any kind of hard water?
the carbonate ions react with the magnesium and calcium ions forming an insoluble precipitate of calcium carbonate and magnesium carbonate, so the calcium and magnesium ions are no longer left meaning that it cannot be classed as hard water anymore.
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How do ion exchange columns work?
The columns contain sodium/hydrogen ions which are exchanged for magnesium and calcium ions when the hard water runs through them. Once there is no longer any calcium or magnesium ions in the water then it is not technically classed as hard water.
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Explain the brief steps in the titration of water samples to compare their hardness?
1.Soap is added to the burette 2. Water is added to the flask underneath. 3. Measure how many cm^3 of soap needs to be added to the water to produce a good lather (where bubbles remain on the surface of the water for at least 30 seconds.)
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What would happen if the samples of water for titration were boiled?
This would get rid of any temporary hard water.
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True or false, the more soap needed to form the lather the softer the water?
False
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What most water be rid of before it is safe to drink?
Poisonous salts and microbes
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What is the first stage in water treatment?
Water passed through mesh screen to get rid of twigs and bits of dirt
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What is the 2nd stage of water treatment?
Chemicals are added so that bits of microbes stick together and fall to the bottom.
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What is the 3rd stage of water treatment?
Water is filtered through gravel beds to get rid of these solids.
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What is the 4th stage of water treatment?
Chlorine is added to get rid of any leftover microbes.
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Why is distillation not used to filter out tap water?
Because it would take too much energy to boil all the water and energy equates to money.
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What is the advantage of having fluoride in our tap water?
It is good for our teeth.
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What is the disadvantage of having fluoride in our tap water?
It can supposedly cause bone cancer.
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Other cards in this set

Card 2

Front

What 2 things does hard water form with soap?

Back

Scum and scale

Card 3

Front

Is scum soluble or insoluble?

Back

Preview of the front of card 3

Card 4

Front

When will scale form?

Back

Preview of the front of card 4

Card 5

Front

Where is scale usually found?

Back

Preview of the front of card 5
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