Unit 2- Green chemistry

Question 1

What are the 5 key principles of green chemistry?

Answer 1

• Changing to renewable sources
• Using energy more efficiently
• alternatives to hazardous materials
• Developing new catalyst
• Reducing waste and preventing pollution

Question 2

What are greenhouse gases?

Answer 2

• Gases which have polar bonds allowing the molecule to absorb IR radiation
• Can be a result from bond vibration and bending allowing the molecule to absorb IR
• e.g. Water vapour and methane

Question 3

What is the greenhouse effect?

Answer 3

• When the suns ultraviolet radiation is emiited
• Either reflected back into space, absorbed by greenhouse molecules or reaces the earths surface
• The energy that is radiated back into space, some is absorbed by the greenhouse gases as the energy is reflected back as IR
• The greenhouse gases trap the IR , thus trapping the heat
• Keeps the earth at a stable temperature

Question 4

What is the enhanced greenhouse effect?

Answer 4

• An increase in the greenhouse effect
• Can be due to an increased number of greenhouse gases
• Causes the earth surface to heat up too much
• leads to global warming

Question 5

What is anthroprogenic changes?

Answer 5

• Change brought out by human activity
• e.g. deforestation, burning fossil fuels and use of CFC’s

Question 6

What is a carbon footprint?

Answer 6

• measures the total amount of greenhouse gases produced by a process

Question 7

What is carbon neutrality?

Answer 7

• Actions for when the amount of greenhouse gases released is balanced by the amount of greenhouse gases taken in
• e.g. plants through photosynthesis

Question 8

Why are biofuels argued about?

Answer 8

• Said to be carbon neutral
• Due to photosynthesis
• Therefore only releases the amount of carbon dioxide that was taken in
• However other cost of bio fuels
• e.g. producing the biofuel, running and using machinery

Question 9

What is the ozone layer?

Answer 9

• a layer in the earths atmopshere made up of O₃

Question 10

How is ozone formed?

Answer 10

• O₂ is split up into O free radicals under UV light
• The O free radicals react with O₂ to form ozone (O₃)
• Ozone is affected by UV light breaking up into O₂ and O free radicals
• Continual process breaking and reforming ozone

Question 11

Why have CFC’s been banned?

Answer 11

• CFC’s along with other halogen compounds are highly unreactive
• Does not break down
• Goes into the stratosphere, where it is broken down by UV light forming compounds such as hydrogen chloride (HCl)

Question 12

What is the reaction between chlorine and ozone?

Answer 12

• Chlorine formed from the reactions with CFC’s will break down ozone in sunlight
• Cl₂ breaks down into Cl free radicals under UV light
• The Cl free radical reacts with ozone to form ClO free radicals and O₂
• ClO free radicals react with O free radicals to form Cl free radicals and O₂
• The overall reaction is O free radical reacting with Ozone to form 2O₂

Question 13

What is the alternative to CFC’s used?

Answer 13

• HCFC (hydrochlorofluorocarbons)
• Used as solvents and refrigerants

Question 14

What is the reaction between Ozone and nitrogen oxide?

Answer 14

• ​Ozone breaks down under UV light to form O₂ and O free radical
• NO reacts with ozone to form NO₂ and O₂
• The NO₂ reacts with O free radicals to form NO and O₂
• The overall reaction is 2O₃ breaks down into 3O₂

Question 15

How is NO formed?

Answer 15

• From microorganisms in the soil and oceans
• Reduces nitrogen compounds