Chapter 10

Question 1

Chemical tests for water: anhydrous copper (III) sulfate

Answer 1

. Method: add a few drops of your test solution to white anhydrous copper (III) sulphate
. Positive test: turns from white to blue

Question 2

Chemical tests for water: anhydrous cobalt (II) chloride

Answer 2

. Method: add a few drops of your test solution to blue cobalt (II) chloride paper
. Positive test: turns from blue to pink (+ gets hot)

Question 3

Test for purity of water

Answer 3

. Pure: contains one substance -> has defined properties
. Method:
1) heat sample in a beaker over a Bunsen
2) use a thermometer to measure the temperature at which the sample changes from a liquid to a gas
. Positive test: if you find boiling point isn’t 100°C (or melting point 0°C -> solid to liquid) then sample isn’t pure

Question 4

Water: water used in practical chemistry

Answer 4

. Distilled water is used rather than tap water as it contains fewer chemical impurities -> These can interfere with reactions and give experiments of false result

Question 5

Water: water from natural resources

Answer 5

• water from natural resources aren’t pure -> contains impurities, which are useful or harmful substances

Question 6

Water: water from natural resources -> useful substances

Answer 6

. Dissolved oxygen: for aquatic life
. Some metal compounds: provide essential minerals for aquatic life

Question 7

Water: water from natural resources -> harmful substances

Answer 7

. Some metal compounds: are toxic
. Sewage: contains harmful microbes, which cause disease
. Some plastics: harm aquatic life
. Nitrate + phosphates: lead to deoxygenation of water and damage to aquatic life

Question 8

Treatment of domestic water supply: filtration and sedimentation

Answer 8

. Removes solids

Question 9

Treatment of domestic water supply: carbon filtration

Answer 9

. Removals tastes and oudours

Question 10

Treatment of domestic water supply: chlorination

Answer 10

. Kills microbes

Question 11

Fertilisers: NPK fertilisers

Answer 11

. Fertlisers containing nitrogen, phosphorus and potassium -> for improved plant growth
- E.g. ammonium salts are nitrates are used as fertilisers

Question 12

Air composition

Answer 12

. 78% nitrogen
. 21% oxygen
. Remaining 1% is a mixture of noble gases and carbon dioxide (0.04%)

Question 13

Air pollutants: carbon dioxide -> source an adverse effect

Answer 13

. Source: complete combustion of carbon containing fuels
. Adverse effect: higher levels of carbon dioxide lead to increased global warming -> climate change

Question 14

Air pollutants: carbon monoxide -> source and adverse effect

Answer 14

. Sources: incomplete combustion of carbon containing fuels.
. Adverse effects: toxic gas

Question 15

Air pollutants: particulates -> source an adverse effect

Answer 15

. Source: incomplete combustion of carbon containing fuels.
. Adverse effect: increase risk of respiratory problems and cancer

Question 16

Air pollutants: methane -> source and adverse effect

Answer 16

. Source: decomposition of vegetation and waste gases from digestion in animals
. Adverse effect: higher levels of methane lead to increased global warming -> climate change

Question 17

Air pollutants: oxides of nitrogen -> source and adverse effect

Answer 17

. Source: car engines
. Adverse effect: acid rain, photochemical smog and respiratory problems.

Question 18

Air pollutants: sulphur dioxide -> source an adverse effect

Answer 18

. Source: combustion of fossil fuels, which contain sulphur compounds
. Adverse effect: acid rain

Question 19

Greenhouse gases

Answer 19

. Greenhouse gases: gases such as methane and carbon dioxide, which cause global warming

Question 20

Greenhouse gases: process

Answer 20

1) the Sun emits thermal energy, which passes through earths atmosphere
2) some of this thermal energy is reflected back into space + rest absorbed by earths surface
3) earths surface then emits thermal energy back out towards space
-> greenhouse gases act like an insulating layer and absorb most of the thermal energy that would normally be lost into space and re-emit it in all directions including back towards the Earth -> this warms the earths surface

Question 21

Reducing climate change: planting trees

Answer 21

. Planting trees: carbon dioxide is removed from the atmosphere by plants during photosynthesis -> in the presence of chlorophyll and using energy from light

Question 22

Reducing climate change: reduction in livestock farming

Answer 22

Lowers methane emissions

Question 23

Reducing climate change: decreasing use of fossil fuels

Answer 23

. Lowers carbon dioxide emissions

Question 24

Reducing climate change: increasing use of hydrogen and renewable energy

Answer 24

(eg wind, solar)
. Lower is carbon dioxide emissions

Question 25

Reducing acid rain: reducing emissions of sulphur dioxide

Answer 25

Use of low-sulphur fuels and flue gas desulfurization with calcium oxide

Question 26

Reducing acid rain: use of catalytic converters in vehicles

Answer 26

. Large amounts of energy released by combustion of fuel causes nitrogen and oxygen in air to react together -> catalytic converters reduce oxides of nitrogen by forming nitrogen and oxygen gas