Air and water

Question 1

Describe chemical tests for water

Answer 1

Anhydrous copper (II) sulphate turns white to blue
Cobalt (II) chloride turns blue to pink

Question 2

Describe, in outline, the treatment of the water

Answer 2

filtration

chlorination (kills bacteria) (pg181)

Question 3

Name some of the uses of water in industry and in

the home

Answer 3

Home: cooking and drinking, washing, cleaning
Industry: solvent for chemicals, as coolant to prevent overheating processes, generate electrical power

Question 4

Describe the composition of clean air

Answer 4

79 % nitrogen, 20 % oxygen 1% as being a mixture of noble gases, water
vapour and carbon dioxide

Question 5

Name the common pollutants in the air

Answer 5

carbon monoxide, sulfur dioxide, oxides of nitrogen

and lead compounds

Question 6

Separation of oxygen and nitrogen from liquid air by

Answer 6

fractional distillation

Question 7

State the source of each of these pollutants:
– carbon monoxide
– sulfur dioxide
– oxides of nitrogen

Answer 7

– carbon monoxide from the incomplete
combustion of carbon-containing substances
– sulfur dioxide from the combustion of fossil fuels
which contain sulfur compounds lead to acid rain
– oxides of nitrogen from car exhausts

Question 8

Use of catalytic converters (cc)

Answer 8

Fitted into a car exhaust to remove poisonous gas

• Exhaust gases are passed through honeycomb in the cc which is covered with a thin layer of catalyst made of platinum, rhodium or palladium.
• React with these catalysts
• First compartment: metals catalyse the conversion of nitrogen oxides to nitrogen
• Second: carbon monoxide is converted to co2

Question 9

Describe methods of rust prevention

Answer 9

• Paint/oil/coat in plastic
• Electroplating/galvanising
• Sacrificial protection: when using more reactive metal to protect a less reactive metal from corrosion. For example: zin is more reactive -> oxidised -> forms zinc ions -> zinc ions corrodes rather than iron.

Question 10

State the 2 greenhouse gases and may contribute to climate change

Answer 10

methane and carbon dioxide

Question 11

Describe the essential conditions for the

manufacture of ammonia by the Haber process including the sources of the hydrogen and nitrogen

Answer 11

• Eq: N2 + 3H2 -> 2NH3 (reversible reaction)
• Nitrogen (extracted by fr.dist.) : Hydrogen (CH4 +H2O -> CO +3H2) = 1:3
• High pressure shifts the equilibrium in the direction of lower volume => moves right. But high pres is expensive => 200atm (compromise rate, yield and cost)
• High temperature: increase in temp favour endothermic => moves to left. However, low temp -> low rate of reaction => 450 degrees celsius.

Question 12

Describe the formation of carbon dioxide

Answer 12

– as a product of complete combustion of carboncontaining
substances
– as a product of respiration
– as a product of the reaction between an acid and
a carbonate
– from the thermal decomposition of a carbonate

Question 13

State the sources of methane

Answer 13

decomposition of vegetation and waste gases from

digestion in animals