Hard Water

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  • Created by: EllieR15
  • Created on: 15-02-15 19:02
What makes hard water?
Calcium Ions and Magnesium Ions
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What two things does hard water create?
Scale and scum
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What happens when soft water and hard water react with soap?
Soft water and soap creates a lather. Hard water and soap creates scum.
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Why does hard water and soap create scum?
The dissolved calcium ions and magnesium ions, in the water, react with the soap to create scum which is insoluble - meaning that it is impossible to dissolve.
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What is formed when hard water is heated?
Scale
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Where is scale usually produced?
Pipes, boilers, kettles etc.
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Why is scale bad?
It reduces the efficiency of heating systems and so boilers, for example, may need to be replaced which costs money.
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Hard water isn't always a bad thing. Why?
Calcium ions are good for healthy teeth and bones. It also reduces the risk of developing heart disease. This could be to do with the minerals in the water.
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How can you make hard water soft?
Remove the calcium ions and magnesium ions.
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What are the two types of hardness?
Temporary and permanent.
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What causes temporary hardness and permanent hardness?
Temporary = The hydrogencarbonate ion. Permanent = Dissolved calcium sulfate (among other things)
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How can you remove temporary hardness?
Boiling. When heated, the calcium hydrogencarbonate decomposes to form calcium carbonate which is insoluble. The solid formed is 'limescale'. This won't work for permanent hardness, however. Heating a sulfate ion does not do anything!
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What is the equation for this?
calcium hydrogencarbonate --> calcium carbonate + water + carbon dioxide
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How can you soften both types of hardness?
Add washing soda (sodium carbonate) to it. The added carbonate ions react with the calcium and magnesium ions to make an insoluble precipitate of calcium carbonate and magnesium carbonate. Another way is by running it through an ion-exchange column.
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What is an ion-exchange column?
Both types of hardness can be softened by running the water through an ion-exchange column. These columns contain lots of sodium ions (or hydrogen ions) and 'exchange' them for calcium or magnesium ions in the water that runs through them.
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How can you compare the hardness of water samples?
Titration
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Other cards in this set

Card 2

Front

What two things does hard water create?

Back

Scale and scum

Card 3

Front

What happens when soft water and hard water react with soap?

Back

Preview of the front of card 3

Card 4

Front

Why does hard water and soap create scum?

Back

Preview of the front of card 4

Card 5

Front

What is formed when hard water is heated?

Back

Preview of the front of card 5
View more cards

Comments

nadiya dabharia

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helped me a lot thanx  :)

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