Chemistry Unit 1 and 2 exams

Sorry? Most of the long-answer questions seem to be on topics of green chemistry or sustainability of reactions. I'm doing the AS syllabus.

Long answer? Biggest I've seen is like 4 marks. This is Unit 2?
Well, I guess just evaluate the case study. Always use the information they give you. If it's not common sense from your Chemistry textbook then it's probably in the text they give you in the exam. Lookout for greenhouse gases, and how to explain their effect, and look out for CFC's and chlorine compounds and be able to explain the risks, uses and benefits of CFC's, eg. they aren't flammable, aren't reactive, are used as refrigerents.

They can link Green chemistry to polymer manufacture and addition polymerisation, so have a look at that. Hope this helps.

Thanks

What are the risks of using CFCs? And why might we want to use an alternative as a refrigerant instead?

Well, even though they're unreactive, if UV light breaks the Carbon Fluorine bond, you're going to generate Chlorine free radicals which you can explain the dangers and effects of. It's so important to read the case study.
Then, also learn definitions such as Greenhouse Gas, Carbon Neutral, Carbon Footprint, examples of Biofuels. Sustainable alternatives to manufacturing things from fossil fuels. What are the problems associated with transporting hydrogen for electrolysis etc.

If you're asked to give uses of CFCs, you can include propellents, aerosols, refrigerants.

You wouldn't have to know chemicals/alternatives off the top of your head. They'll give you a case study and ask you to evaluate it compared to current methods (ie, the CFCs). Just use what you know to sift through the information, like look for positives of other chemical processes that they give you. Does it have a high atom economy? Percentage yield?

What other benefits might it have; how many moles of CO2 does it produce compared to other methods they give you? Look for financial and environmental benefits.

Well, even though they're unreactive, if UV light breaks the Carbon Fluorine bond, you're going to generate Chlorine free radicals which you can explain the dangers and effects of. It's so important to read the case study.
Then, also learn definitions such as Greenhouse Gas, Carbon Neutral, Carbon Footprint, examples of Biofuels. Sustainable alternatives to manufacturing things from fossil fuels. What are the problems associated with transporting hydrogen for electrolysis etc.

If you're asked to give uses of CFCs, you can include propellents, aerosols, refrigerants.

You wouldn't have to know chemicals/alternatives off the top of your head. They'll give you a case study and ask you to evaluate it compared to current methods (ie, the CFCs). Just use what you know to sift through the information, like look for positives of other chemical processes that they give you. Does it have a high atom economy? Percentage yield?

What other benefits might it have; how many moles of CO₂ does it produce compared to other methods they give you? Look for financial and environmental benefits.

Good key point.

Well, even though they're unreactive, if UV light breaks the Carbon Fluorine bond, you're going to generate Chlorine free radicals which you can explain the dangers and effects of. It's so important to read the case study.
Then, also learn definitions such as Greenhouse Gas, Carbon Neutral, Carbon Footprint, examples of Biofuels. Sustainable alternatives to manufacturing things from fossil fuels. What are the problems associated with transporting hydrogen for electrolysis etc.

If you're asked to give uses of CFCs, you can include propellents, aerosols, refrigerants.

You wouldn't have to know chemicals/alternatives off the top of your head. They'll give you a case study and ask you to evaluate it compared to current methods (ie, the CFCs). Just use what you know to sift through the information, like look for positives of other chemical processes that they give you. Does it have a high atom economy? Percentage yield?

What other benefits might it have; how many moles of CO₂ does it produce compared to other methods they give you? Look for financial and environmental benefits.

Less moles of CO₂ (or any greenhouse gas) is what we would aim for from any reaction, correct?



Thanks, this is great stuff. Do you have anything else to say? (James A?)

Moles? Wouldn't it be better to talk about the mass/volume of CO2 given off?

When you see cars advertised, they usually give the CO2 output (efficiency of an engine) as in Kg (mass) per mile or km. Moles is always the same for CO2, but mass and volume varies



Nope, that's all

Moles? Wouldn't it be better to talk about the mass/volume of CO2 given off?

When you see cars advertised, they usually give the CO2 output (efficiency of an engine) as in Kg (mass) per mile or km. Moles is always the same for CO2, but mass and volume varies

Nope, that's all

Yeah, it's all relative, but what you've said makes better sense
It doesn't really make too much of a difference surely though, what I meant was let's say one method of combustion produces 2 moles of CO2 per mole of fuel burnt, and another method produces 1 mole of CO2 per mole of fuel burnt, surely the second option is the better one to use with regards to emission of Greenhouse gases?

I understand it's a bit weird to be talking about moles of gases when volume makes more sense.

Remember as well, the issues discussed in Unit 2 about fuels, concern everyday members of the public, therefore moles would be confusing to them, but mass given off, or volume given off, gives a clear cut about which fuel has more of a greenhouse effect on the environment. It's sounds silly me saying this because after all, it is a chemistry paper we're doing, but these topics concern everyone, not just people who study/take an interest in chemistry.

2 days till unit 1 exam guys. I'm not feeling very confident. How are you guys feeling?


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