Unit 11: Air and Water

Question 1

What are two methods of testing for water?

Answer 1

1. Water will turn anhydrous copper sulfate from white to blue.
2. Water will turn anhydrous cobalt chloride from blue to pink.

Question 2

How is the water supply purified?

Answer 2

1. The water is filtered through coarse sand to remove the larger insoluble particles. It is then filtered through a finer sand.
2. Chlorine gas is added to kill any remaining bacteria.

Question 3

What are the uses of water used for industrial purposes?

Answer 3

Mainly for cooling and irrigation purposes.

Question 4

What is the composition of air?

Answer 4

1. 78% nitrogen
2. 21% oxygen
3. 1% a mixture of carbon dioxide and noble gases.

Question 5

What are the main pollutants in the air?

Answer 5

1. Carbon monoxide
2. Sulfur dioxide (can contribute to acid rain)
3. Oxides of nitrogen (can also contribute to acid rain)
4. Lead compounds

Question 6

What is the main source of the pollutant carbon monoxide?

Answer 6

The incomplete combustion of carbon containing substances.

Question 7

What is the main source of the pollutant sulfur dioxide?

Answer 7

From the combustion of fossil fuels which contain sulfur compounds.

Question 8

What is the main source of the polluting oxides of nitrogen?

Answer 8

From car engines.

Question 9

What is the main source of the polluting lead compounds?

Answer 9

The combustion of leaded petrol.

Question 10

What are the main affects of the pollutants in the air?

Answer 10

Acid rain can dissolve some cement products and the mortar in brick work, it can also attack some metals. Lead compounds and carbon monoxide are poisonous. Sulfur dioxide and nitrogen oxides can cause problems for asthmatics.

Question 11

What are the conditions required for the rusting of iron?

Answer 11

Water and oxygen.

Question 12

How can rusting and corrosion be prevented?

Answer 12

1. Painting.
2. Covering in grease.
3. Plastic covering (mainly for wires).
4. Plating in another metal.

Question 13

How are oxygen and nitrogen separated from the air?

Answer 13

The air is compressed and cooled below the b.p. of both oxygen and nitrogen so the air becomes a liquid.
The air is allowed to warm slowly and the nitrogen boils off before the oxygen because it has a lower boiling point.

Question 14

How are nitrogen oxides formed in car engines?

Answer 14

Under the high pressures and temperatures in the engines of motor vehicles, nitrogen and oxygen can combine to form oxides of nitrogen.

Question 15

How are nitrogen oxides removed from car exhausts?

Answer 15

A catalytic converter converts the oxides of nitrogen into less harmful gases like nitrogen and carbon dioxide. Catalytic converters only work with unleaded petrol because lead will harm the catalytic converter.

Question 16

What is sacrificial protection and how does it work?

Answer 16

Where iron is galvanised with zinc. Zinc is higher on the reactivity series so is more reactive than iron so will corrode and go into solution first, only when all of the zinc has corroded will the iron begin to rust.

Question 17

Why are nitrogen, phosphorus and potassium fertilisers needed?

Answer 17

Plants need things like nitrogen to make plant proteins. It must be absorbed into the soil in a soluble form (ex. nitrates). When plants are harvested, this nitrogen is taken away from the soil in the plants, so the soil needs fertilisers to add these nutrients back to the soil.

Question 18

How is ammonia displaced from its salts?

Answer 18

Look back at older topic.

Question 19

What are the essential conditions for the manufacture of ammonia in the Haber process?

Answer 19

Look back at older topic.

Question 20

How do carbon dioxide and methane contribute to climate change?

Answer 20

They interact with infrared radiation and slow down heat loss to space from the atmosphere, with more carbon dioxide and methane, less heat is escaping so temperatures are rising.

Question 21

What are the ways in which carbon dioxide can be formed?

Answer 21

1. As a product of the complete combustion of carbon-containing substances.
2. As a product of respiration.
3. As a product of the reaction between an acid and a carbonate.
4. From the thermal decomposition of a carbonate.

Question 22

What are the sources of methane?

Answer 22

1. The decomposition of vegetation.

2. As a waste gas from digestion in animals.

Question 23

What are the steps in the carbon cycle?

Answer 23

1. Carbon enters the atmosphere as carbon dioxide from respiration and combustion.
2. Carbon dioxide is absorbed by producers to make carbohydrates in photosynthesis.
3. Animals feed on the plant passing the carbon compounds along the food chain. They exhale carbon dioxide formed during respiration. The animals and plants eventually die.
4. The dead organisms are eaten by decomposers and the carbon in their bodies is returned to the atmosphere as carbon dioxide. The plant and animal material may then be available as fossil fuel in the future for combustion.

Question 24

What are some tests for ammonia?

Answer 24

1. It turns damp red litmus blue.

2. It forms a white smoke when it reacts with hydrochloric acid fumes.

Question 25

What are some of the uses of ammonia?

Answer 25

1. To make nitric acid.

2. To make fertilisers ammonium nitrate and ammonium sulfate.

Question 26

What is the water of crystallisation?

Answer 26

Ionic solids often have molecules of water bonded into their ionic crystal lattice. This water is called the water of crystallisation.

Question 27

What is deliquescence?

Answer 27

Substances that absorb water from the atmosphere sufficiently enough to form a solution are said to be deliquesent. Ex. Calcium chloride hexahydrate CaCl2 . 6H2O and sodium hydroxide, NaOH.

Question 28

What is efflorescence?

Answer 28

Substances that are efflorescent lose some or all of their water of crystallisation upon exposure to the atmosphere. Ex. Sodium carbonate decahydrate, Na2CO3 . 10H2O.

Question 29

What is a hydroscopic substance?

Answer 29

A substance that gains water from the atmosphere, but not enough to form a solution. Ex. Na2CO3.

Question 30

What are dehydrating agents?

Answer 30

Substances that remove the atoms required to make up water from certain substances. Ex. Sulfuric acid.