2.3 the wider impact of chemistry

Question 1

what is the main problem surrounding energy?

Answer 1

• the huge and increasing amounts of energy required that is mostly provided by the combustion of non-renewable fossil fuels with the associated release of carbon dioxide into the atmosphere and oceans

Question 2

due to, at present consumption rates, the fossil fuels will diminish and their cost increase, what alternative sources are being considered?

Answer 2

• include nuclear power, solar energy and biomass fuels
• the aim to achieve carbon neutrality

Question 3

what does carbon neutrality mean?

Answer 3

e.g the CO2 generated in combustion of the biomass is compensated for by that absorbed during the photosynthetic growth of the plants

Question 4

make it very clear when describing atom economy that this is based on mass or relative molecular mass and not on the number of molecules in the equation

Answer 4

do not use the word ‘amount’ since this is connected vie ‘amount of substance’ to the number of moles

Question 5

nuclear power info:

Answer 5

• well established
• contributing around 20% of fuel needs
• efforts now focus on making it safer
• produced by the fission of uranium
• only a small amount of uranium is needed to start the reaction but there can be problems of disposing safely of radioactive waste or of emissions
• fusion of hydrogen to form helium would be a better solution, without creating hazardous products but this requires a huge amount of heat and pressure so a viable way of doing this has yet to be found

Question 6

what does solar power use to obtain increased efficiency and reliability?

Answer 6

• uses semiconductor chemistry

but efficiency varies with sun exposure

Question 7

pros of using hydrogen as fuel?
cons of using hydrogen as fuel?

Answer 7

• no CO2 is produced during its combustion
• howvee hydrogen doesn’t occur naturally on Earth
• costly in terms if the energy needed for the electrolysis process
  (efforts are being made to form it through the electrolysis of water)

Question 8

what is the aim of green chemistry?

Answer 8

• to make the chemicals and products that we need with as little impact on the environment as possible

Question 9

what are some aims of green chemistry?

Answer 9

• using as little energy as possible (and getting this from renewable sources. generally increase energy efficiency)
• using renewable raw materials (feedstock) such as plant-bases compounds whenever possible
• using methods having high atom economy so that a high percentage of the mass of reactants ends up in the product, giving little waste
• developing better catalysts, such as enzymes, to carry out reactions at lower temps and pressures to save energy and avoiding constructing strong plants
• avoid using solvents, especially volatile organic solvents that are bad for the environment
• make products that are biodegradable at the end of their useful lives
• avoid using toxic materials if possible and ensure that no undesirable co-products or by-products are released into the environment to prevent pollution

Question 10

summary of green chemistry aims:

Answer 10

• use renewable energy resources
• keep energy use to a minimum/low temperature/low pressure
• use the most effective catalyst
• use non-toxic materials whenever possible
• the co-products should be non-toxic/or capable of being converted to non-toxic materials
• use renewable feedstocks/sustainable feedstocks
• reuse /recycle waste product
• high atom economy

Question 11

which fuel is potentially carbon neutral?

Answer 11

biomass
it should absorb the same amount of carbon dioxide in its growth cycle as it releases when burnt. howvee there may be additional carbon dioxide emissions created in its use from harvesting and transport

Question 12

examples of non-renewable fuel:

Answer 12

• coal
• oil
• gas

Question 13

what is an environmental problem associated with sulfur dioxide SO2?

Answer 13

it forms acid rain

Question 14

what is an environmental problem associated with carbon dioxide CO2?

Answer 14

contributes to global warming

Question 15

what does a higher atom economy mean for the amount of useful product produced?

Answer 15

higher atom economy = more useful products (so the more sustainable the reaction)

Question 16

what is chemical synthesis?

Answer 16

the process of carrying out specific chemical reactions in order to produce a desired compound

Question 17

what does sustainable chemistry mean?

Answer 17

chemistry that is carried out with the intention to not use up the earth’s resources and to limit the amount of pollutants released

Question 18

what should be considered when choosing a reaction pathway to synthesis a desired product?

Answer 18

• availability of reactants
• least waste produced (high atom economy)
• fewest stages possible
• fastest rate of reaction
• safe reaction conditions

Question 19

how do you calculate atom economy?

Answer 19

Mr of desired product / total Mr of reactants x100

Question 20

explain the economic impacts of chemical synthesis:

Answer 20

• provides jobs for people involved in the production
• there is a demand for the chemical being produced, like medicine, so the product will generally be economically valuable

Question 21

explain the social impacts of chemical synthesis:

Answer 21

• allows for important products like drugs and polymers to be produced which help people in everyday life

Question 22

explain the environmental impacts of chemical synthesis:

Answer 22

the synthesis route with the lowest environmental impact should be chosen:
- if has renewable reactants as this improves sustainability
- highest economy and minimum waste
- where conditions dont require a lot of energy bc less pollutants released

Question 23

explain the environmental effects of energy production:

Answer 23

• energy is commonly produced from the burning of fossil fuels (finite resource so not a sustainable source of energy. they also release harmful gases e.g CO2 when burned which contribute to global warming)
• energy can be produced from renewable sources like solar and tidal, which is good as it’s sustainable and doesnt release harmful gases. but these energy sources are much less common

Question 24

what is a catalytic converter?

Answer 24

• fitted in a car to convert the harmful carbon monoxide (CO) and oxides of nitrogen (NOx) emissions to less harmful carbon dioxide and nitrogen

2CO + 2NO —> 2CO2 + N2

Question 25

what are the environmental impacts of acid rain?

Answer 25

• corrodes buildings and statues made of limestone
• kills vegetation
• lowers the pH of large bodies of water, killing the wildlife

Question 26

NO(g) + CO(g) + O2(g) -> NO2(g) + CO2(g)
the reaction shown is one of many that are catalysed in a catalytic converter. state where in a car a catalytic converter is used and name a suitable catalyst. [2]

Answer 26

catalytic converter used in: exhaust
catalyst used :
- heterogenous
- a transition metal / a transition metal period