Air and water

Question 1

What are two chemical tests for water?

Answer 1

Cobalt (II) chloride: turns from blue to pink

Copper (II) sulfate: turns white to blue

Question 2

What are two problems associated with lack of water?

Answer 2

Water used to irrigate crops - Crops cannot grow → lack of food for populations reliant on crops
No safe water for drinking: increased risk of disease

Question 3

Describe the process of treatment of water supply (6)

Answer 3

1. Water passed through metal screens and filtered for twigs/leaves
2. In settlement tank, soil particles settle at bottom
3. Aluminum sulfate added to make small particles in water stick together. Particles fall to bottom of tank
4. Passed through filter made of sand and gravel, removes any insoluble particles not removed
5. Chlorine added to kill bacteria
6. pH of water adjusted, water run off

Question 4

What are the uses of water in industry and in the home?

Answer 4

Generate electricity

Cooking, washing, cleaning

Question 5

What is the composition of clean, dry air?

Answer 5

78% nitrogen, 21% oxygen and remainder: mixture of noble gases/carbon dioxide

Question 6

Describe the separation of oxygen and nitrogen by fractional distillation (4)

Answer 6

1. Water + carbon dioxide removed from air
   - Water by passing it through a drying agent
   - carbon dioxide by reacting it with sodium hydroxide
2. Air is cooled to -23 degrees celcius and compressed
3. Cold compressed air allowed to expand in larger space, air cools when expand until temp. drops to -200 degrees celcius - air is liquid
   - Argon, krypton and xenon are removed from oxygen by further distillation
4. When liquid air is warmed, nitrogen boils off first (lower boiling point) + condenses
5. Mixture fed to top column, oxygen condenses, nitrogen gas residue removed at top

Question 7

What are the four common pollutants in the air?

Answer 7

carbon monoxide
sulfur dioxide
oxides of nitrogen
lead compounds

Question 8

What are the sources + effects of carbon monoxide?

Answer 8

S:
incomplete combustion of carbon-containing substances
E:
reacts w/ haemoglobin, prevents from carrying oxygen, death

Question 9

What are the sources + effects of sulfur dioxide?

Answer 9

S:
combustion of fossil fuels which contain sulfur compounds
E:
irritates eyes and throat, causes respiratory problems and acid rain

Question 10

What are the sources + effects of oxides of nitrogen?

Answer 10

S:
car engines
denitrification
high temperature furnaces
E:
causes respiratory problems and acid rain

Question 11

What are the sources + effects of lead compounds?

Answer 11

S:
burning of petrol
E:
causes damage to brain + nerve cells in young children

Question 12

Describe the process of catalytic conversion of oxides of nitrogen in car engines (5)

Answer 12

Exhaust gases from car engine passed through a honeycomb (surface covered with metal catalysts) in a catalytic converter
Two compartments:
Compartment 1: metals catalyse conversion of nitrogen oxides to nitrogen
2NO(g) → N2(g) + O2(g)
2NO2(g) → N2(g) + 2O2(g)
Compartment 2: Carbon monoxide converted to carbon dioxide
2CO(g) + O2(g) → 2CO2(g)
Carbon monoxide may also react directly with nitrogen oxides (nitric acid + nitrogen dioxide)

Question 13

What is needed for iron to rust?

Answer 13

Water and Oxygen

Question 14

What are the four methods of rust prevention?

Answer 14

Paint
Plastic Coating
Galvanising
Sacrificial Protection

Question 15

What is galvanising?

Answer 15

coating iron with zinc

Question 16

What is sacrificial protection?

Answer 16

blocks of more reactive metal attached to iron surface

Question 17

What are NPK fertilizers used for?

Answer 17

replace essential elements lost when plants are harvested

Question 18

What causes the displacement of ammonia from its salts in soil?

Answer 18

Too much lime put in soil, displaces ammonia from ammonium salts, lost as gas

Question 19

What is ammonia’s function in soil

Answer 19

To neutralise soil acidity

Question 20

What is the Haber process?

Answer 20

Industrial manufacture of ammonia NH3

Question 21

What is the equation for the Haber process?

Answer 21

N2 (g) + 3H2 (g) ⇌ 2NH3 (g)

Question 22

What are the raw materials required for the Haber process?

Answer 22

Nitrogen: from the air

Hydrogen

Question 23

What are the essential conditions required for the Haber process?

Answer 23

Temperature: 450°C
Pressure: 200 atm
Catalyst: Iron

Question 24

How does methane cause global warming?

Answer 24

Absorb heat energy and prevent it escaping into space - global warming

Question 25

How does carbon dioxide cause global warming?

Answer 25

heat is absorbed by carbon dioxide and becomes trapped within the Earth’s atmosphere → Earth becomes hotter

Question 26

What are the three ways carbon dioxide is formed?

Answer 26

Product of complete combustion of carbon containing substances
Product of respiration
Production of reaction between an acid and a carbonate

Question 27

What is the function of the carbon cycle?

Answer 27

keeps concentration of carbon dioxide in atmosphere constant

Question 28

What are the three main processes in the carbon cycle?

Answer 28

combustion, respiration, photosynthesis

Question 29

What is the equation for testing of water? (copper sulfate)

Answer 29

CuSO4(s) + 5H2O => CuSO4.5H2O(s)

Question 30

What is the equation for testing of water? (cobalt (II) chloride)

Answer 30

CoCl2 (s) + 6H2O (l) => CoCl2.6H2O

Question 31

Is treated water pure?

Answer 31

No

Question 32

What are the two oxides of nitrogen formed in internal combustion engines?

Answer 32

Nitric oxide: N2 + O2 → 2NO(g)

Nitrogen oxide: N2 + 2O2 → 2NO2(g)

Question 33

Why do oxides of nitrogen form in internal combustion engines?

Answer 33

Due to the high temperature and pressure inside an internal combustion engine which causes nitrogen and oxygen to combine