C11 Air and water

Question 1

What is the composition of clean air?

Answer 1

The composition of clean air:
78% Nitrogen
21% Oxygen
Small quantities of noble gases, water vapour and carbon dioxide

Question 2

What are the common pollutants in the air?

Answer 2

Common pollutants in the air:
Carbon monoxide
Sulfur dioxide
Oxides of nitrogen

Question 3

What are the sources of carbon monoxide?

Answer 3

Sources of carbon monoxide:
Incomplete combustion of fossil fuels e.g. incomplete combustion of gasoline.

Question 4

What are the adverse effects of carbon monoxide?

Answer 4

Carbon monoxide is poisonous.
When it combines with the haemoglobin in blood, it prevents it from carrying oxygen.

Question 5

What are the sources of sulfur dioxide?

Answer 5

The sources of sulfur dioxide include the combustion of fossil fuels containing sulfur compounds e.g. power stations.

Question 6

What are the adverse effects of sulfur dioxide?

Answer 6

When sulfur dioxide dissolves in rain, it forms acid rain which causes corrosion to metal structures, buildings and statues made of carbonate rocks, and damages aquatic organisms. It also pollutes crops and water supplies and irritates the lungs, throat and eyes and causes respiratory problems.

Question 7

What are the sources of oxides of nitrogen?

Answer 7

The sources of oxides of nitrogen include the reaction of nitrogen with oxygen in the presence of high temperatures e.g. in car engines, high temperature furnaces and when lightening occurs. it is also a product of bacterial action in soil.

Question 8

What are the adverse effects of oxides of nitrogen?

Answer 8

-Produces photochemical smog.
-Dissolves in rain to form acid rain.
-Corrosion to metal structures, buildings and studs made of abrogate rocks.
-Damage to aquatic organisms.
-Pollutes crops and water supplies.
-Irritates lungs, throats and eyes.
-Respiratory problems.

Question 9

What is the greenhouse effect?

Answer 9

The greenhouse effect is:
-Sun emits energy in form of radiation that enter Earth’s atmosphere.
-Some thermal energy is reflected from the Earth’s surface.
-Most thermal energy is absorbed and re-emitted back.
-However, some is absorbed by greenhouse gases such as carbon dioxide and is re-emitted in all directions.
-This reduces the thermal energy lost into space and traps it within the Earth’s atmosphere, keeping the Earth warm.

Question 10

What is the enhanced greenhouse effect?

Answer 10

The ehanced greenhouse effect is that the concentration of greenhouse gases in the atmosphere increases due to human activity, more thermal energy is trapped within the Earth’s atmosphere causing the Earth’s average temp to rise (global warming).

Question 11

How to reduce the emissions of sulfur dioxide?

Answer 11

Emissions of sulfur dioxide can be reduced by:
-Using fuels which contain low levels of sulfur.
-Flue gas desulfurisation - this involves reacting the sulfur dioxide emitted from burning fuels containing sulfur, with calcium oxide, therefore removing it from the flue gas.

Question 12

How do oxides of nitrogen form?

Answer 12

Oxides of nitrogen are formed when nitrogen and oxygen react in the high pressure and temperature conditions of internal combustion engines and blast furnaces.

Question 13

What are cars fitted with?

Answer 13

cars are fitted with catalytic converters which form a part of they exhaust systems.

Question 14

What do catalytic converters contain?

Answer 14

Catalytic converters contain a series of transition metal catalysts including platinum and rhodium.

Question 15

What are the metal catalysts in within the converter?

Answer 15

The metal catalysts are in a honeycomb within the converter to increase the surface area available for reaction. A series of redox reactions occur which neutralises the pollutant gases.

Question 16

What happens in this stage 2CO + O2 → 2CO2

Answer 16

2CO + O2 → 2CO2 shows carbon monoxide being oxidised to carbon dioxide.

Question 17

What happens in this stage 2NO → N2 + O2

2NO2 → N2 + 2O2

Answer 17

Oxides of nitrogen re reduced to N2 gas.

Question 18

What is the equation that summarises the reaction of nitrogen monoxide and carbon monoxide within a catalytic converter?

Answer 18

2NO + 2CO → N2 + 2CO2

Question 19

What gases go in a catalytic converter and what come out?

Answer 19

Carbon monoxide (CO), Nitrogen oxide (NO) and oxygen (O2) enters.
Carbon dioxide (CO2), Nitrogen (N2) and Oxygen (O2) comes out.

Question 20

What is rusting?

Answer 20

Rusting is a special type of corrosion that occurs when iron (or steel) reacts with water and oxygen.

Question 21

What are the conditions needed for the rusting of iron?

Answer 21

The presence of oxygen and water are needed for rusting.

Question 22

What is the word equation for rusting?

Answer 22

Iron + water + oxygen => hydrated iron oxide

Question 23

How can rust be prevented?

Answer 23

Rust can be prevented by coating iron with barriers that prevent the iron from coming into contact with water and oxygen.
However, if the coatings are washes away or scratched, the iron is once again exposed to water and oxygen and will rust.

Question 24

What are common barrier methods?

Answer 24

-Grease
-Oil
-Paint
-Plastic
These will prevent rusting but only if they completely cover up the iron.

Question 25

How else can iron be prevented from rusting?

Answer 25

Iron can also be prevented from rusting by using the reactivity series.

Question 26

What is sacrificial protection?

Answer 26

Sacrificial protection is when a more reactive metal is attached to a less reactive metal. The more reactive metal will oxidise and therefore corrode first, protecting the less reactive metal from corrosion.
-The more reactive metal is sacrificed to protect the less reactive metal (iron or steel).
For continued protection, the reactive metal needs to be replaced before they completely corrode.

Question 27

What is galvanising?

Answer 27

Galvanising is a process where the iron to be protected is coated with a layer of zinc. This can be done by electroplating or dipping it into molten zinc. If the coating is damaged or scratched, the iron is still protected from rusting by sacrificial protection.

Question 28

By what is carbon dioxide produced?

Answer 28

– as a product of complete combustion of carbon-containing substances
– as a product of respiration
– as a product of the reaction between an acid and a carbonate
– as a product of thermal decomposition of calcium carbonate

Question 29

Explain how carbon dioxide is produced in complete combustion of carbon containing substances.

Answer 29

Most fuels contain carbon and so when they burn they produce carbon dioxide:
CH4(g) + 2O2(g) ———–> CO2(g) + 2H2O(l)
methane + oxygen ——> carbon dioxide + water

Question 30

Explain how carbon dioxide is produced in respiration.

Answer 30

Respiration is the process by by which living beings gain energy from food. Glucose in food combines with the oxygen we breathe in to produce carbon dioxide and water.
C6H12O6 + 6O2 ————> 6CO2 + 6H20
glucose + oxygen ———> carbon dioxide + water

Question 31

Explain how carbon dioxide is produced in the reaction between an acid and a carbonate.

Answer 31

CACWS
When an acid reacts with a carbonate, carbon dioxide is produced along with water and a salt.

Question 32

Explain how carbon dioxide is produced in thermal decomposition.

Answer 32

Thermal decomposition is the breaking down of compounds into two or more products using heat. When compounds containing carbon such as calcium carbonate are thermally decomposed, they produce carbon dioxide.

Question 33

What are carbon dioxide and methane?

Answer 33

Carbon dioxide and methane are greenhouse gases.