Chemistry of the environment Details/Definitions

Question 1

Chemical reaction of water and anhydrous copper(II) sulfate

Answer 1

CuSO₄(s) + 5H₂O(l) → CuSO₄.5H₂O(s)

Question 2

Water turns anhydrous copper(II) sulfate…

Answer 2

from white to blue

Question 3

Chemical reaction of water and anhydrous cobalt(II) chloride

Answer 3

CoCl₂(s) + 6H₂O(l) → CoCl₂.6H₂O(s)

Question 4

Water turns anhydrous cobalt(II) chloride…

Answer 4

from blue to pink

Question 5

How to test for the purity of water using melting and boiling points

Answer 5

-Heating it and observing when it boils(pure water should have a boiling point of 100°C; If we heat a liquid and it begins to boil either below or above 100°C, the liquid contains impurities)

-Cooling it and observing when it freezes(pure water should have a freezing point of 0°C; If we cool a liquid and it begins to freeze either below or above 0°C, the liquid contains impurities.)

Question 6

Why is distilled water used instead of practical water in chemistry

Answer 6

Distilled water contains fewer chemical impurities

Question 7

Substances in water

Answer 7

-Dissolved oxygen
-Metal compounds
-Plastics
-Sewage
-Harmful microbes
-Nitrates from fertilizers
-Phosphates from fertilizers and detergents

Question 8

Beneficial substances in water

Answer 8

-Dissolved oxygen(for aquatic life)
-Some metal compounds(provide essential minerals for life)

Question 9

Potentially harmful substances in water

Answer 9

-Some metal compounds(are toxic)
-Some plastics(harm aquatic life)
-Sewage(contain harmful microbes which cause disease)
-Nitrates and phosphates(lead to deoxygenation of water and damage to aquatic life)

Question 10

Process of treatment of domestic water supply

Answer 10

-Sedimentation and filtration(to remove solids)
-Use of carbon(to remove tastes and odours)
-Chlorination(to kill microbes)

Question 11

Chlorination

Answer 11

The process of adding chlorine to drinking water in order to kill parasites, bacteria and viruses

Question 12

Ammonium salts and nitrates are used as…

Answer 12

fertilisers

Question 13

Use of NPK(nitrogen/phosphorus/potassium) fertilizers

Answer 13

Provide the elements nitrogen, phosphorus and potassium in the soil for improved plant growth

Question 14

Percentage of nitrogen in clean, dry air

Answer 14

78%

Question 15

Percentage of oxygen in clean, dry air

Answer 15

21%

Question 16

Apart from nitrogen and oxygen, clean air also contains…

Answer 16

a mixture of noble gases and carbon dioxide

Question 17

Source of carbon dioxide

Answer 17

The complete combustion of carbon-containing fuels

Question 18

Source of carbon monoxide and particulates

Answer 18

The incomplete combustion of carbon-containing fuels

Question 19

Source of methane

Answer 19

-The decomposition of vegetation and waste gases from digestion in animals
-Cracking hydrocarbons

Question 20

Source of oxides of nitrogen

Answer 20

Car engines

Question 21

Source of sulfur dioxide

Answer 21

Acid rain

Question 22

How greenhouse gases carbon dioxide and methane cause global warming

Answer 22

They absorb, reflect and emit thermal energy into the atmosphere, hence reducing the amount of thermal energy lost to space

Question 23

Strategies to reduce the effect of climate change

Answer 23

-Planting trees
-Reduction in livestock farming
-Decreasing use of fossil fuels
-Increasing use of hydrogen and renewable energy(eg. wind, solar, etc.)

Question 24

Strategies to reduce the effect of acid rain

Answer 24

-Use of catalytic converters in vehicles
-Reducing emissions of sulfur dioxide(by using low sulfur fuels and flue gas desulfurization with calcium oxide)

Question 25

Photosynthesis

Answer 25

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

Question 26

Word equation for photosynthesis

Answer 26

Carbon Dioxide + Water → Glucose + Oxygen

Question 27

Symbol equation for photosynthesis

Answer 27

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Question 28

How catalytic converters remove oxides of nitrogen

Answer 28

They catalyse the reaction between carbon monoxide and nitrogen monoxide, forming nitrogen and carbon dioxide.

Question 29

How oxides of nitrogen form in car engines

Answer 29

NB: Nitrogen does not react with oxygen at room temperature
-Despite this, the high temperatures in car engines exceeds the activation energy of the reaction, causing nitrogen and oxygen to react together to form oxides of nitrogen

Question 30

Chemical reaction at catalytic converters

Answer 30

2CO + 2NO → 2CO₂+ N₂