Scum is formed, as Calcium or Magnesium ions react with soap to form scum
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What happens when you heat hard water?
Scale is formed (mostly calcium carbonate)
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What are the problems with scale?
Blocks pipes, drains, and reduces the efficiency of heating systems
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Why is scale bad for kettles?
Acts as a thermal insulator so the kettle takes longer to boil
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What causes hard water?
The calcium and magnesium ions that come from dissolved rocks by rain, such as limestone, chalk and gypsum
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Name the two types of hardness
Temporary and permanent
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What are the benefits of hard water?
Ca2+ ions are good for teeth and bones, and hard water has been linked to reduced heart disease risk because of the minerals
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What is temporary hardness caused by?
The hydrocarbonate ion (HCO3-) in calcium hydrocarbonate
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What is permanent hardness caused by?
Dissolved calcium sulfate
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How do you remove temporary hardness?
Boiling. When heated, calcium hydrocarbonate decomposes to make calcium carbonate which is insoluble. Ca(HCO3)2 ---> CaCO3 + CO2
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Why can't you get rid of permanent hardness by boiling?
Heating a sulfate ion does not thermally decompose it.
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How can adding sodium carbonate remove both types of hardness?
Add the sodium carbonate to it. The carbonate ions react with the calcium and magnesium ions to make an insoluble precipitate of calcium carbonate and magnesium carbonate.
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How can an ion exchange column remove both types of hardness?
The columns have sodium or hydrogen ions in them, and when water runs through, and the calcium and magnesium ions are exchanged.
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What is the equation for an ion exchange column with sodium ions?
Na2 RESIN + Ca2 ---> Ca RESIN + 2Na+
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What is the equation for adding sodium carbonate to the calcium ions in hard water?
Ca2+ + CO3 2- ---> CaCo3
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Other cards in this set
Card 2
Front
What happens when you lather hard water?
Back
Scum is formed, as Calcium or Magnesium ions react with soap to form scum
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