Chapter 19: Water

Question 1

Hard water

Answer 1

Water that does not easily form a lather in soap

Causes by Ca2+ or Mg2+ ions I’m water

Question 2

How is Scum formed

Answer 2

Calcium or magnesium ions react with stearate ions to form calcium stearate (scum)

Question 3

Temporary Hardness

Answer 3

One that can be removed by boiling water

• Caused by calcium hydrogen carbonate

Question 4

Permanent Hardness

Answer 4

Hardness that cannot be removed by boiling

Magnesium sulfate, calcium sulfate

Question 5

Methods of Removing Hardness

Answer 5

Distillation
Zeolites
Washing soda
Ion-exchange resin

Question 6

Distilled water

Answer 6

Purest form

All dissolved and suspended solids and all dissolved gases removed

Question 7

Buffer Solution

Answer 7

A solution that resists changes in pH

Question 8

Water Treatments Stages

Answer 8

Screening 
Flocculation 
Sedimentation 
Filtration 
Chlorination 
Fluoridation 
pH adjustment

Question 9

Flocculation

Answer 9

The coagulating of small suspended particles in water

Aluminium sulfate

Question 10

Primary Treatment

Answer 10

Screening

Channels Settlement

Question 11

Secondary Treatment

Answer 11

Oxidation and aeration of sewage

Micro-organisms decompose sewage

Question 12

Tertiary Treatment

Answer 12

Prevention of eutrophication by removing nitrates and phosphates

Question 13

Instruments to Analyse Water

Answer 13

pH measurement
AAS - Atomic Absorption Spectrometry
Colorimetry

Question 14

Colorimetry

Answer 14

Amount of absorbance of light is proportional to the concentration of the solution

Question 15

Free Chlorine

Answer 15

Chlorine that exists in the water as hypochlorous acid and hypochlorite ion

Question 16

What produces hypochlorous acid

Answer 16

Calcium hypochlorite

Question 17

Combined chlorine

Answer 17

Chemicals combined with ammonia or organic nitrogen compounds in water