Topic 10: Chemistry of the Environment

Question 1

Why is water important?

Answer 1

1. More than 70% of the earth is covered in water
2. Main components of all living things
3. Neutral, colourless, odourless
4. Amphoteric - can act as a base or acid
5. A universal solvent

Question 2

What are the two chemical tests for water?

Answer 2

Test 1:
Anhydrous copper (II) sulfate turns white to blue when water is added
CuSO4 + 5H2O —> CuSO4SH2O

Test 2:
Anhydrous cobalt (II) chloride turns from blue to pink when water/aqueous solution is added
CoCl2 + 6H2O —-> CoCl26H2O

Question 3

How do you test the purity of water?

Answer 3

By measuring its boiling point, since it has a fixed boiling point (100 degrees) and fixed freezing point (0 degrees)

Question 4

How do you know if water is impure?

Answer 4

It won’t boil at exactly 100 degrees.

Question 5

Why is distilled water used in many experiments?

Answer 5

Because it is very pure and does not contain many of these impurities, which may affect the outcome of the experiments.

Question 6

What substances does water dissolve?

Answer 6

1. A variety of gases from the air, such as carbon dioxide and oxygen.
2. Nitrates and phosphates from agricultural waste and detergents
3. Metal compounds from industrial wastewater
4. Human waste from sewage
5. Insoluble impurites such as oil and plastic waste

Question 7

How is water treated?

Answer 7

1. Sedimentation: separates out solids from the water
2. Filtration: separate additional solids from the water. Activated carbon filters remove bad odours. Usage of ultrafiltration
3. Disinfection: chemical disinfectants like chlorine are added to kill remaining harmful microorganisms

Question 8

What do fertilisers contain? Why?

Answer 8

They contain salts of:
Nitrogen
Phosphorous
Potassium

These elements are essential to plant growth and since they can’t be absorbed as a pure element they are used in the form of soluble salts.

Question 9

What are NPK fertilisers?

Answer 9

Fertilisers that contain nitrogen, phosphorous and potassium

Question 10

Why do plants need nitrogen?

Answer 10

To make the leaves grow

Question 11

Why do plants need phosphorous?

Answer 11

Improves fruit/flower production as well as root growth

Question 12

Why do plants need potassium?

Answer 12

For overall plant health

Question 13

What type of salts are used as fertilisers?

Answer 13

Ammonium salts and nitrates.

Question 14

Tell me the composition of air.

Answer 14

78% nitrogen
21% oxygen
1% other gases

Question 15

Why is carbon dioxide harmful?

Answer 15

1. Causes greenhouse effect due to excessive burning of fossil fuels.
2. Increase in greenhouse gases causes the average temperatures to rise, warming the climate

Question 16

Why is carbon monoxide harmful?

Answer 16

1. Poisonous even in low concentrations
2. Reacts with the haemoglobin in the blood and prevents it from carrying oxygen around the body - you will die from oxygen starvation.

Question 17

Why is methane harmful?

Answer 17

1. Primary contributor to the formation of ground-level ozone, a hazardous air pollutant and greenhouse gas
2. 80 times more potent at warming than CO2

Question 18

Why are nitrogen oxides harmful?

Answer 18

1. Causes respiratory problems, and dissolves in the rain to give acid rain

Question 19

Why is sulfur dioxide harmful?

Answer 19

Irritates the eyes and throat and causes respiratory problems.
Dissolves in the rain to form acid rain which attacks stoneworks in buildings, kills trees and insects and lowers the pH of rivers and lakes.

Question 20

Why are particulates harmful?

Answer 20

Long term exposure to particulate matter can be associated with increased rates of chronic bronchitis, reduced lung function and increased mortality from lung cancer and heart disease

Question 21

How do you reduce effects of global warming?

Answer 21

1. Plant more trees
2. Reduce deforestation
3. Reduce livestock farming
4. Burn fewer fossil fuels by using alternative methods
5. Use renewable energy sources
6. Fit a catalytic converter to the exhaust system of the vehicles
7. Use scrubbers to reduce the amounts of sulfur dioxide from flue gases

Question 22

What does a catalytic converter do?

Answer 22

Reduces the amount of nitrogen oxide emitted by car exhausts by converting it into nitrogen and carbon dioxide. Carbon dioxide and nitrogen are much less dangerous to a person’s health than carbon monoxide and nitrogen monoxide (the rationale behind this)