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# OCR Salters (legecy) Chemistry By Design (2854) Revision Thread watch

1. (Original post by Loz17)
I thought was only to say that the reaction was spontaneous
So i just read it up:
- If ∆H sol is -'ve, or slightly +'ve, then the solid dissolves. like you said, entropy change is preferred.
- If ∆H sol is large and +'ve then the solid will NOT dissolve. This is because too much energy is needed.
2. thanks everyone! so helpful , im gonna start revision now, good luck
3. (Original post by l.learner)
Does anyone have some good exam and revision techinique for this paper?
This exam is the most inconsistent and wide ranging answers.

The best technique would be to adjust to the longer theoretical question given to you (as if you're doing an english exam).

The mathematical questions, break it down, and apply formula, this takes practice. But theyre relatively easy part of the exam.

the one mark question, you either know the answer or you don't
4. (Original post by zapstec)
I thought this was the last sitting for this exam?
OCR arent gay like AQA. Theyre running coursework and all A2 units till the summer.
5. (Original post by zapstec)
So i just read it up:
- If ∆H sol is -'ve, or slightly +'ve, then the solid dissolves. like you said, entropy change is preferred.
- If ∆H sol is large and +'ve then the solid will NOT dissolve. This is because too much energy is needed.
That is correct. However I'd love to really understand where entropy comes into it though

I'll look it up somewhere it doesn't explain it in CI
6. (Original post by Loz17)
That is correct. However I'd love to really understand where entropy comes into it though

I'll look it up somewhere it doesn't explain it in CI
The solid is dissolved in solution therefore the entropy has increased as a result of the G>L>S entropy thingy? (more particles hence more combinations stuff also?)
7. (Original post by Fatal_Microbes)
The solid is dissolved in solution therefore the entropy has increased as a result of the G>L>S entropy thingy? (more particles hence more combinations stuff also?)
Ohh right

so simple

Thanks
8. I'm only guessing, but going through oceans now =)
but that would be logical from my readings.
Hence the energy amount preventing it even though its a +entropy change.

But still, they were wrong about the direction of electron flow so who knows =D
9. I've never been through oceans. I never looked at it when we did it in lessons coz I was too busy doing c/w at the time for chem. So it was a bit rushed.

I've only done the actual chemistry for it.
10. (Original post by Loz17)
I've never been through oceans. I never looked at it when we did it in lessons coz I was too busy doing c/w at the time for chem. So it was a bit rushed.

I've only done the actual chemistry for it.
Had a quick question, if we don't get the grades this jan, can we resit again in summer?
11. (Original post by freddyy_poo)
Had a quick question, if we don't get the grades this jan, can we resit again in summer?
I didnt think we could.. but these guys here say we can... since its OCR.
I knew OCR were allowing resits in june, but I didnt realise salters was part of this (Stupid.. i know...)
12. (Original post by freddyy_poo)
Had a quick question, if we don't get the grades this jan, can we resit again in summer?
Yea we can
13. niceeee!
14. I need to basically get revison for this done today, but biology takes priority as I feel less confident in it and its tomorrow. I have tomorrow evening to revise solely chemistry and thats it
15. (Original post by Loz17)
I need to basically get revison for this done today, but biology takes priority as I feel less confident in it and its tomorrow. I have tomorrow evening to revise solely chemistry and thats it
I swear down I'm in the same position as you! Got Snab biology tomorrow and it's the last time they're doing the exam; so I've gotta focus on that today.
16. (Original post by l.learner)
I swear down I'm in the same position as you! Got Snab biology tomorrow and it's the last time they're doing the exam; so I've gotta focus on that today.
It sucks doesn't it I don;t have any of tuesday to revise this module either. I work 9-5 then I have a psychlogy lesson 6-9 in the evening and will have no time in the morning of the exam. I'll do a tiny bit later but as soon as my exam finishes tomorrow I'm home and revising this!!

Anyone know what to do regarding calculations? I am terrible at them (minus the ones where you plug numbers in)
17. (Original post by Loz17)
Anyone know what to do regarding calculations? I am terrible at them (minus the ones where you plug numbers in)
Which ones in particular?
18. (Original post by Fatal_Microbes)
Which ones in particular?
Anything that isn't as I can do all them
19. (Original post by Loz17)
Anything that isn't as I can do all them

Thats all there is though bar what percentage purity and yield?
20. (Original post by Fatal_Microbes)
Thats all there is though bar what percentage purity and yield?
Yea its percentage yields, ratios and that I can't do

Someone on here showed me a good way of doing it but I struggle with the method of it.

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