Green Chemistry

Question 1

What is GWP?

Answer 1

Global Warming Potential: a measure of how much a given gas can contribute to global warming over a given time period.

Question 2

State the factors that affect GWP

Answer 2

1. The ability of a gas to absorb infrared radiation

2. The half life of a greenhouse gas

Question 3

What is the difference between natural climate change and anthropogenic climate change?

Answer 3

Natural climate change is caused by nature (e.g. Volcanic eruptions, sunspot activity)
Anthropogenic climate change is climate change caused by human activity (e.g. Deforestation, agriculture, burning fossil fuels - CO2 levels rise & ice caps melt)

Question 4

What does carbon neutral mean?

Answer 4

An activity where the amount of CO2 absorbed by plants in producing the fuel is equal to the amount of CO2 released when the fuel is burnt.

Question 5

What is a greenhouse gas?

Answer 5

A gas that absorbs infrared radiation from the earth, and changes its polarity when it’s bonds vibrate by stretching or bending.

Question 6

What is a biofuel?

Answer 6

A liquid or gas fuel derived from biomass. Can be made from methanol and algae in transesterification.

Question 7

State two advantages and two disadvantages of biofuels.

Answer 7

Advantages

1. CO2 is absorbed from growing plant
2. Renewable resource

Disadvantages

1. Energy is required to transport fuel
2. Land used to grow fuel reduces food supply

Question 8

What is hydrogen fuel and is it renewable?

Answer 8

Fuel made from natural gas or the electrolysis of water.

No CO2 emissions produced when fuel is burnt but CO2 is produced in manufacturing & distribution.

Question 9

What is meant by carbon footprint?

Answer 9

A measure of the impact of human activity on the environment.

Question 10

Explain how carbon offsetting works.

Answer 10

It involves reducing the effect of of carbon footprint by paying the cost, planting new trees.
Carbon capture, using renewable fuels

Question 11

State the advantages and disadvantages of CFCs

Answer 11

Advantages:
1. CFCs have several uses in aerosols, refrigerants, polystyrene, fire retardants
(Use in retardants may be supported because CFCs with strong C-F bonds don’t release fluorine radicals)
2. High volatility, non-flammable, non-toxic and extremely unreactive

Disadvantages:

1. CFCs build up in the atmosphere and cause depletion of the ozone layer
2. CFCs are greenhouse gases - contribute to global warming

Question 12

What is sustainability?

Answer 12

Development that encourages the design of processes to reduce the generation of hazardous substances.
It involves conserving resources for future generations.

Question 13

State and explain two principles of sustainability.

Answer 13

1. Changing to renewable resources - reduce the use of non-renewable resources like fossil fuels by producing biofuels from wheat, fermentation etc.
2. Reducing waste - improve atom economy (use by-products)
3. Reduce pollution - reduce waste

Question 14

What is ozone?

Answer 14

A poisonous (toxic) gas that filters out the sun's UV radiation.
In the lower atmosphere ozone is a pollutant that contributes to the formation of smog.

Question 15

How is ozone formed from UV light?

Answer 15

O2 + UV light -> O + O
O + O2 -> O3
Ozone also reforms oxygen in:
O3 + UV light -> O2 + O
Rate of formation = rate of removal

Question 16

How do NOx contribute to the depletion of the ozone layer?

Answer 16

NO + O3 -> NO2 + O2
NO2 + O -> O2 + NO
Overall: O3 + O -> 2O2

Question 17

What are the problems with scaling up a laboratory process?

Answer 17

1. Lower yield
2. More toxic reagents
3. Energy costs of separating product
4. Cost of reagent