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Chemistry > Water Ch. 20 > Flashcards

Water Ch. 20 Flashcards

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1
Q

What is Hard Water?

A

Water that will not form a lather easily with soap.

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2
Q

What is Temporary Hardness?

A

Hardness in water that can be removed by boiling.

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3
Q

What is Temporary Hardness caused by?

A

Hydrogencarbonate anions (Mg(HCO3)2 or Ca(HCO3)2

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4
Q

Chemical formula for temporary hardness

A

H2O + CO2 + CaCO3 -> Ca(HCO3)2

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5
Q

What happens when you boil temporary hardness?

A

Ca(HCO3)2 + Heat -> CaCO3 + CO2 + H2O
Forms Limescale

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6
Q

What is Permanent Hardness?

A

Hardness in water that can only be removed by methods other than boiling (ion exchange, distillation, deionization)

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7
Q

What is Permanent Hardness caused by?

A

Caused by the chlorides and sulfates of calcium and magnesium.

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8
Q

What is Ion Exchange?

A

Involves the water being passed through a resin where the Mg++ or Ca++ is replaced by Na+ ions
2RNa + Ca++ -> R2Ca +2Na+

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9
Q

What is Deionization?

A

Cations that cause Hardness are replaced by H+ ions and Anions are replaced by OH-, they then combine to form H2O resulting in no ions being in the water.

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10
Q

What is Distillation?

A

Removes not only the ions from the water but also the suspended solids and gases contained within the water, resulting in a pure distillate.

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11
Q

How do you distinguish between carbonate and hydrogencarbonate?

A

Add Magnesium Sulfate, the carbonate forms a precipitate while the hydrogencarbonate does not.

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12
Q

How do you test for Sulfate anions?

A

Both Sulfate and Sulfate anions react with Barium Chloride to form a white precipitate, you can then distinguish between the two by adding HCL, Barium Sulfite reacts while the Sulfate does not.

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13
Q

How to test for chlorine anions?

A

Chlorine anions react with silver nitrate to form a white precipitate of silver chloride.

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14
Q

How to test for nitrate anions?

A

Using cold freshly prepared Iron(II) sulfate and slowly adding concentrated sulfuric acid after a few moments a brown ring will form. (Known as “Brown Ring Test”)

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15
Q

How do you test for phosphate anions?

A

Using ammonium molybdate and concentrated nitric acid, you warm the solution gently to no greater than 40°C and a yellow precipitate should form if the anions are present.

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16
Q

What are the steps for water treatment?

A

Flocculation, Sedimentation, Filtration, Chlorination, Fluoridation, pH adjustment

17
Q

Name a flocculating agent

A

Aluminium Sulfate

18
Q

What is Flocculation?

A

Small particles clump together to facilitate settlement

19
Q

What is Sedimentation?

A

Water is allowed to stand in tanks, allowing suspended particles to sink to the bottom.

20
Q

What is Chlorination

A

Chlorine or sodium hypochlorite added to water to kill pathogens and micro organisms

21
Q

What is Fluoridation?

A

Fluoride ions are added to prevent tooth decay

22
Q

How is the pH of water adjusted?

A

Lime is added to acidic water, or sulfuric acid added to alkaline water to adjust the range of the pH to 6-8

23
Q

What is the primary treatment of sewage

A

Involves screening and settlement, and it is a physical process which removes solids.

24
Q

What is secondary treatment?

A

Is a biological process involving the oxidation by micro-organisms of the nutrients present in effluent.

25
Q

What is tertiary treatment?

A

Involves the removal of phosphates and nitrates from the effluent.

26
Q

What is Eutrophication?

A

The presence of excess nutrients in a water body causing over abundant plant growth.

27
Q

What are the causes of Eutrophication?

A

Untreated sewage, run off from farmland of slurry or fertilizers.

28
Q

What is heavy metal pollution caused by?

A

Mercury, cadmium and lead

29
Q

What are some sources of heavy metals?

A

Car batteries containing lead or dry batteries containing cadmium.

30
Q

What are the effects of heavy metals in water?

A

They are cumulative poisons that can cause serious health damage such as foetal abnormalities or minimata disease.

31
Q

How are heavy metals removed from water?

A

By means of precipitation.

Chemistry (8 decks)

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