10 Chemistry of the Environment

Question 1

Cobalt Chloride test for water

Answer 1

Blue when anhydrous, Pink when hydrated

Question 2

test for purity of water

Answer 2

boils at exactly 100C

Question 3

Why is distilled water used in practical chemistry rather than tap water

Answer 3

Distilled water contains less impurities

Question 4

What will water from natural sources contain?

Answer 4

dissolved oxygen, metal compounds, plastics, sewage, harmful microbes, nitrates from fertilisers, phosphates from fertilisers and detergents

Question 5

What are the beneficial impurities that water from natural resources contain

Answer 5

• dissolved oxygen for aquatic life
• some metal compounds provide essential minerals for life

Question 6

What are the harmful impurities that water from natural resources contain

Answer 6

• some metal compounds are toxic,
• some plastics harm aquatic life
• sewage contains harmful microbes which cause disease
• nitrates and phosphates lead to deoxygenation of water and damage to aquatic life

Question 7

treatment of the domestic water

Answer 7

1) sedimentation and filtration to remove solids
2) use of carbon to remove tastes and odours
3) chlorination to kill microbes

Question 8

What are used as fertilisers?

Answer 8

Ammonium, phosphates, nitrates and potassium salts

Question 9

Composition of gases in the air:

Answer 9

Nitrogen 78%, Oxygen 21%, Argon 0.9%, Carbon dioxide 0.04%

Question 10

Source of carbon dioxide

Answer 10

Complete combustion of carbon containing fuels

Question 11

Source of carbon monoxide

Answer 11

Incomplete combustion of carbon-containing fuels

Question 12

Source of methane

Answer 12

Decomposition of vegetation and waste gases from digestion in animals

Question 13

Source of nitrogen oxides

Answer 13

combustion of air at high temperatures in car engines or produced during thunder storms

Question 14

Source of sulfur dioxide

Answer 14

combustion of fossil fuels which contain sulfur compounds

Question 15

Adverse effects of Carbon dioxide

Answer 15

increased global warming which leads to climate change

Question 16

Adverse effects of carbon monoxide

Answer 16

toxic gas - binds to haemoglobin in the blood, reducing the ability of blood to carry oxygen

Question 17

Adverse effects of particulates (e.g. carbon)

Answer 17

increased risk of respiratory problems and cancer

Question 18

Adverse effects of methane

Answer 18

increased global warming, which leads to climate change

Question 19

Adverse effects of oxides of nitrogen

Answer 19

acid rain, photochemical smog, respiratory problems

Question 20

Adverse effects of sulfur dioxide

Answer 20

acid rain

Question 21

How to reduce the effects of cllimate change?

Answer 21

planting trees, reduction in livestock farming, decreasing use of fossil fuels, increasing use of hydrogen and renewable energy

Question 22

How to reduce the effects of acid rain?

Answer 22

a) use of catalytic converters in vehicles
- removes oxides of nitrogen
b) reducing emissions of sulfur dioxide by using low-sulfur fuels
c) flue gas desulfurisation with calcium oxide
- reacting SO2 with CaO to remove it from the flue gas

Question 23

photosynthesis

Answer 23

reaction between carbon dioxide and water to produce glucose and oxygen in the presence of chlorophyll and using energy from light

Question 24

Explain how oxides of nitrogen form in car
engines and describe their removal by catalytic converters

Answer 24

The high temperature and pressure inside an internal combustion engine causes nitrogen and oxygen to combine. A mixture of different nitrogen oxides are then formed. To remove carbon monoxide and nitrogen oxides, a catalytic converter can be fitted to a car exhaust. By converting the oxides of nitrogen into carbon dioxide and nitrogen. 2CO + 2NO → 2CO2 + N2

Question 25

How do greenhouse gases cause global warming

Answer 25

Greenhouse gases absorb thermal energy from the earth (1)
- energy from the sun is absorbed by the earth’s surface
- Earth emits or reflects thermal energy
- Greenhouse gases reduces or stops thermal energy loss (into space)
- increasing in amount of greenhouse gases results in higher atmospheric temperature