OCR AS Salters May 23rd Exam Thread 2014

What's nuclear fission, I don't remember doing this at all? Is it just where radioactive isotopes break down releasing radiation?

Reply 26

OP

Original post by 7jdrabble

I am doing this paper tomorrow as well as the F332 and both A2 papers. I don't think tomorrows paper will be too bad providing it doesn't vary from much from previous years, It seemed the physics one on tuesday which i took was a little different from expected but even then it wasn't horrendous! Last minute advice which i'm sure you know already, DO THE PAST PAPERS! Having done them all, and now working through them again, the similarities are so obvious. The same 2,3, or even 4 mark questions come up constantly so be sure to know the answers from the markschemes! Good luck to everyone tomorrow!

Have you done the past papers before 2009?

Reply 27

OP

Original post by BrokenS0ulz

What's nuclear fission, I don't remember doing this at all? Is it just where radioactive isotopes break down releasing radiation?

I don't think we have to know that. Just nuclear fusion.

Reply 28

BrokenS0ulz

Original post by EggsterminateMe

I don't think we have to know that. Just nuclear fusion.

Oh ok!

You seem smart so could you give me bullet point answers to these? :smile:

Benefits and risks of alternative fuels: "nuclear"
and what are the benefits and risks of fossil fuels?

Reply 29

OP

Original post by BrokenS0ulz

Oh ok!

You seem smart so could you give me bullet point answers to these? :smile:

Benefits and risks of alternative fuels: "nuclear"
and what are the benefits and risks of fossil fuels?

I want to laugh at you for calling me smart.

Advantages of nuclear fuel:
Does not produce carbon dioxide or other kinds of air pollution
Disadvantages: radioactive waste produced, public fear of possibility of a nuclear disaster
Advantage of fossil fuels:
Abundance of them
Disadvantages: burning fuels produces sulfur dioxide which leads to acid rain.
Unburnt hydrocarbons and oxides of NOx contribute to smog

Reply 30

BI0

7

Hi, I'm taking this exam too! ^_^ I would suggest revising reforming/isomerisation/cracking since that comes up quite a bit.

Reply 31

BrokenS0ulz

Original post by EggsterminateMe

I want to laugh at you for calling me smart.

Advantages of nuclear fuel:
Does not produce carbon dioxide or other kinds of air pollution
Disadvantages: radioactive waste produced, public fear of possibility of a nuclear disaster
Advantage of fossil fuels:
Abundance of them
Disadvantages: burning fuels produces sulfur dioxide which leads to acid rain.
Unburnt hydrocarbons and oxides of NOx contribute to smog

Thankyou very much :smile:

!
What do we say for the source of unburnt hydrocarbons? Incomplete combustion of hydrocarbons?
Final question is do we just have to know that oxygenates increase the octane rating and therefore decrease chance of auto ignition and engine damage?

Reply 32

username1082804

Can someone explain to me thermal decomposition/stability?
And why it increases down the group? I really don't get it.

Reply 33

username1082804

Original post by BrokenS0ulz

Thankyou very much :smile:

!
What do we say for the source of unburnt hydrocarbons? Incomplete combustion of hydrocarbons?
Final question is do we just have to know that oxygenates increase the octane rating and therefore decrease chance of auto ignition and engine damage?

The source of unburnt fuel is just unburnt hydrocarbon
And yes, you do! Good luck :smile:

Reply 34

BI0

7

Original post by chococup123

Can someone explain to me thermal decomposition/stability?
And why it increases down the group? I really don't get it.

Yes. This part is a little weird to explain.

Basically, thermal stability refers how stable the (group 2 elements in this context) are when heated. If they are more stable they will require more heat to undergo thermal decomposition

Why it increases down the group: carbonate ions (CO3-) can be distorted in the presence of a positively charged ion (e.g Mg2+). As we go down the group, there is less distortion (because larger atoms have a smaller charge density) which leads to a higher thermal stability.

Reply 35

OP