Hard Water Flashcards Preview

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Flashcards in Hard Water Deck (22)
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1
Q

What is the difference between hard and soft water, with soap?

A

Hard water produces a scum, so you need more soap.

2
Q

What does hard water produce when heated?

A

Furring or scale.

3
Q

What does scale do to heating systems?

A

Reduces efficiency and can block pipes.

4
Q

What is permanent hardness caused by?

A

Dissolved calcium sulfate.

5
Q

Why is water hard?

A

Rain falls on rocks (limestone, chalk, gypsum etc.) and can dissolve compounds like magnesium sulfate or calcium sulfate

6
Q

What are the benefits of hard water?

A
  1. Ca2+ ions are good for teeth and bones

2. Less risk of heart disease

7
Q

What is temporary hardness caused by?

A

Hydrogencarbonate ion, HCO3-.

8
Q

How can temporary hardness be removed?

A

Boiling.

9
Q

Why does boiling remove temporary hardness?

A

The calcium hydrogencarbonate decomposes to form calcium carbonate.

10
Q

Why does adding washing soda remove hardness?

A

The carbonate ions react with the Ca2+ and Mg2+ ions to make an insoluble precipitate.

11
Q

How do ion exchange columns work?

A

The sodium ions are exchanged for calcium or magnesium ions in the water.

12
Q

How can you compare the hardness of water samples?

A

Titration.

13
Q

What diseases can microbes in water cause?

A

Cholera and dysentry.

14
Q

What are the stages of water treatment?

A
  1. Mesh (e.g twigs)
  2. Chemicals (e.g microbes)
  3. Gravel bed (e.g solids)
  4. Chlorination (e.g microbes)
15
Q

What does carbon do in filters?

A

Removes chlorine taste.

16
Q

What does silver do in filters?

A

Kill bugs.

17
Q

How is pure water produced?

A

Distillation.

18
Q

Why isn’t tap water distilled?

A

Too expensive.

19
Q

Why is fluoride added to drinking water?

A

Reduces tooth decay.

20
Q

Why is chlorine added to drinking water?

A

Prevent disease.

21
Q

What is the problem with adding fluoride to drinking water?

A
  1. Can cause cancer and bone problems.

2. People can’t choose not to use tap-water (mass-medication).

22
Q

What is the problem with adding chlorine to drinking water?

A

Can react with natural substances in water to produce toxic by-products.