2.3 Green Chemistry

Question 1

What is the greenhouse effect?

Answer 1

• occurs when greenhouse gases in a planet’s atmosphere trap some of the heat radiated from the planet’s surface, raising its temperature
• contributes to climate change and global warming

Question 2

Name some greenhouse gases

Answer 2

• water vapour
• carbon dioxide
• methane
• CFCs and nitrous oxides

Question 3

How do greenhouse gases become harmful?

Answer 3

• specific bonds within substances absorb IR radiation causing molecules to vibrate and emit energy as radiation

Question 4

Origins and impact of sulphur dioxide

Answer 4

• combustion of fossil fuels
• forms acid rain

Question 5

Origins and impact of carbon monoxide

Answer 5

• incomplete combustion of hydrocarbons
• toxic as impacts O2 transport around body

Question 6

Origins and impact of nitrogen oxides

Answer 6

• car engines
• acid rain and respiratory irritant

Question 7

What are storage options for CO2 produces?

Answer 7

• inject deep underground where converted to liquid and stored in porous rock, ie geological formations and empty oil fields
• react CO2 with stable minerals to from carbonate (v energy intensive)
  —> carbon capture storage

Question 8

What is shale gas and what impact can collecting it have?

Answer 8

• produced by fracking which is used in power stations to make electricity
• subsidence, collapsed grounds, water contamination

Question 9

Name low carbon energy and give some pros/cons

Answer 9

• wind: destroy landscape, noise pollution
• solar: takes up farm land, eyesore
• HEP: disrupts aquatic habitats
• nuclear: radioactive waste, terrorist threat, funding storage, huge structures
  —> lots are v expensive and manufacturing process itself can be damaging

Question 10

Explain the use of biodiesel in cars

Answer 10

• slightly less efficient than current fuel and produces lots of smog
• produced from oil extracted from plants
• replace or added to diesel
• classed as carbon neutral and less exhaust pollution
• crops and farmland used for fuel instead of food

Question 11

Outline hydrogen fuel

Answer 11

• electrolysis of water
• produce v explosive hydrogen gas
• water contamination?

Question 12

Methanol fuel cells are in development. What are pros and cons of this over hydrogen fuel?

Answer 12

Pros: liquid fuel easier to transport than gas, methanol from biomass is renewable
Cons: storing and transporting hydrogen, limited life, high production cost, use of toxic chemicals in production

Question 13

What is a heterogeneous catalyst?

Answer 13

Catalyst that has different physical state to its reactants

Question 14

What is a homogenous catalyst?

Answer 14

Catalyst which has the same physical state to its reactants

Question 15

What is a catalytic converter? How does it work?

Answer 15

• a device used to reduce the emissions from an internal combustion engine
• used in exhaust systems to provide a site for the oxidation and reduction of toxic by-products (like nitrogen oxides, carbon monoxide, and hydrocarbons) of fuel into less hazardous substances such as carbon dioxide, water vapor, and nitrogen gas.

Question 16

Outline the adverse effects of the use of CFCs

Answer 16

• produce chlorine radicals which destroy ozone layer
• ozone layer protects us from UV radiation which causes skin cancer/mutatioms

Question 17

Why have hydrocarbons replaced CFCs in their uses?

Answer 17

• C-C bonds would need to be broken to form radicals
• too strong to be broken by UV radiation

Question 18

What is meant by a carbon neutral fuel

Answer 18

• renewable
• no net change in atmospheric CO2 levels
• ie plant release then absorb