Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chemistry > Water (chpt.19) > Flashcards

Water (chpt.19) Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Chemistry flashcards Periodic Table flashcards Chemistry 101 flashcards Organic Chemistry 101 flashcards
1
Q

Hard water

A

Water that will not easily form a lather with soap

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What causes hardness in water

A

Ca 2+ and Mg 2+ ions dissolved in water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Temporary hardness

A

Hardness that can be removed by boiling the water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Permanent hardness

A

Hardness that cannot be removed by boiling the water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Methods of removing hardness from water

A
  1. Distillation → boiling water, then condensing vapour
    ↳ expensive due to cost of boiling
  2. Using washing soda → exchanges Na 2+ ions for Ca 2+ ions
  3. Ion-exchange resin → swaps positive ions for H+ ions and swaps negative ions for OH-
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Advantages of hard water

A

• Provides calcium for teeth and bones
• Nicer taste
• good for brewing & tanning leather

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Disadvantages of hard water

A

• blocks pipes, leaves scale on kettles and boilers
• wastes soap
• produces scum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Distilled water

A

Purest form of water
All dissolved and suspended solids as well as dissolved gases have been removed from the water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Why is deionised water not as pure as distilled water?

A

Deionised water contains dissolved gases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Is deionised or distilled water purer?
Explain

A

Distilled more pure

Deionised water contains dissolved gases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Flocculation

A

The coming together of small suspended particles in water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Flocculating agent

A

A chemical added to water to coagulate suspended particles and this help sedimentation take place

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Steps in water treatment

A
  1. Screening → water passed through wire mesh to remove debris
  2. Flocculation → small suspended particles brought together by flocculating agents
  3. Sedimentation → water passed into settlement tanks, over 90% of suspended particles removed
  4. Filtration → water passed through large beds of sand, removing any remaining suspended solids
  5. Chlorination → chlorine added to water to sterilise
  6. Fluoridation → small quantities of fluorine compounds added to water, helps reduce tooth decay
  7. pH adjustment → optimum pH is 7.2
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How is the pH of water raised?

A

Add calcium hydroxide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How is the pH of water lowered?

A

Add sulfuric acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Example of flocculating agent

A

Aluminium sulfate

17
Q

Example of fluorine compound added to water during fluoridation

A

Sodium fluoride NaF

Hexafluorosilic acid H2SiF6

18
Q

Buffer solution

A

A solution that resists changes in pH in order to keep pH constant

19
Q

Complexometric titration

A

A titration involving the formation of a complex between metal ions and a reagent such as edta

In this type of titration the end point is marked by a sharp decrease in the concentration of free metal ions

20
Q

Biochemical oxygen demand (B.O.D)

A

The amount of dissolved oxygen consumed by biological action when a sample of water is kept at 20°c in the dark for five days

21
Q

In water treatment, what is the purpose of adding aluminium sulphate

A

Clumping / coagulating fine particles

22
Q

In water treatment, what is the purpose of adding chlorine

A

Kills pathogens

23
Q

In water treatment, what is the purpose of adding sodium fluorosilicate

A

Prevents tooth decay / strengthens enamel

24
Q

In water treatment, what is the purpose of adding calcium hydroxide

A

Raises pH

25
Q

In water treatment, what is the purpose of adding sulfuric acid

A

Lowers pH

26
Q

Why is water pollution by heavy metal ions a cause for concern

A

Toxic

27
Q

Name an instrumental technique that could be used to detect and measure the presence of a heavy metal ion in a water sample

A

Atom absorption spectrometry

28
Q

Give an example of a problem that could arise if the pH of a public water supply was too low

A

Corrosion of pipes

29
Q

Define eutrophication

A

Over enrichment of water with nutrients

30
Q

Harmful effect of eutrophication

A

Algae bloom

Fish kill

31
Q

Suggest one possible cause of eutrophication

A

Slurry / fertiliser run-off

Chemistry (22 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions