You are Here: Home

# OCR A2 CHEMISTRY F324 and F325- 14th and 22nd June 2016- OFFICIAL THREAD Watch

1. (Original post by AqsaMx)
Attachment 538013

Can anyone explain this pls

Henderson-Hasselbalch equation:

pH = pKa + log(A-/HA)

3 = 4 + log(A-/HA)

log(A-/HA) = -1

So the ratio must be 1/10 as 10^-1 = 1/10

Your second answer would be the opposite so 10/1 as you need log(A-/HA) = 1.

I think anyway, I could be missing something.

Posted from TSR Mobile

Henderson-Hasselbalch equation:

pH = pKa + log(A-/HA)

3 = 4 + log(A-/HA)

log(A-/HA) = -1

So the ratio must be 1/10 as 10^-1 = 1/10

Your second answer would be the opposite so 10/1 as you need log(A-/HA) = 1.

I think anyway, I could be missing something.

Posted from TSR Mobile
Thanks!
3. Can someone explain why the reaction between phenol and Na is classed as a redox/reduction reduction, is it become the Carbon oxidation number decreases??

4. Can anyone explain why CH3CH2COCl hydrolysed more readily than CH3CH2CH2Cl??
5. Did a mock for F324 today - it was the June 2015 paper. RIP.
6. (Original post by itsConnor_)
Did a mock for F324 today - it was the June 2015 paper. RIP.
7. (Original post by itsConnor_)
Did a mock for F324 today - it was the June 2015 paper. RIP.
How did it go? I also did it recently and I thought it was hard, but the difficulty was a bit over-hyped.
8. (Original post by Kamara7)
Have you done it? How did you do if so?
9. (Original post by marioman)
How did it go? I also did it recently and I thought it was hard, but the difficulty was a bit over-hyped.
I had a look at it and it was a bit more difficult but if you understood the content it would be fine.
10. (Original post by marioman)
How did it go? I also did it recently and I thought it was hard, but the difficulty was a bit over-hyped.
We're going to get the papers back on Friday but I found it very hard compared to the other past papers (done all F324 and Jan '02-'05 chains, rings, spec) :/

I found the timing really difficult with it also
11. (Original post by itsConnor_)
Have you done it? How did you do if so?
Timing was an issue for me in that particular exam. The NMR was hard to analyse in the amount of time I had left, but looking at it afterwards, I could've got the molecule if I didn't panic and assign one peak stupidly The other question I screwed up was the one where it told you to find the structure of some amino acids and polymers. If I realised that aldehydes can be oxidised to carboxylic acids and not just primary alcohols, then I wouldn't have screwed up the rest of that question I just didn't know what to do because the hydrogens weren't adding up Other than that, it was... meh
12. (Original post by marioman)
How did it go? I also did it recently and I thought it was hard, but the difficulty was a bit over-hyped.
This. The only issue I had with the paper was timing, I think that there were too many questions.
13. (Original post by marioman)
How did it go? I also did it recently and I thought it was hard, but the difficulty was a bit over-hyped.
You're right but you didn't sit the real exam. It's a lot different when your actual grade depends on it and you're sweating in the exam hall with 10 minutes to do the last question.
That's why you always see people claiming they've messed the paper up despite getting 90+% on past papers

Posted from TSR Mobile
You're right but you didn't sit the real exam. It's a lot different when your actual grade depends on it and you're sweating in the exam hall with 10 minutes to do the last question.
That's why you always see people claiming they've messed the paper up despite getting 90+% on past papers

Posted from TSR Mobile
It's not really that different.
15. (Original post by rory58824)
This. The only issue I had with the paper was timing, I think that there were too many questions.
do u print out ur papers or do it on the computer, i advice u print them out somewhere! because i would honestly spent a whole hour more for the unit 5 chem when using computer, when i started printing i finished on time.

Posted from TSR Mobile
16. (Original post by ranz)
do u print out ur papers or do it on the computer, i advice u print them out somewhere! because i would honestly spent a whole hour more for the unit 5 chem when using computer, when i started printing i finished on time.

Posted from TSR Mobile
I print most of them.
17. (Original post by alow)
It's not really that different.
Of course it is. There's no pressure doing past papers.

Posted from TSR Mobile
Of course it is. There's no pressure doing past papers.

Posted from TSR Mobile
If you're confident you've worked hard enough and revised effectively there should be no pressure in the exam.
19. A mixture was prepared using 1.00 mol of propanoic acid, 2.00 mol of ethanol and 5.00 molof water. At a given temperature, the mixture was left to reach equilibrium according to thefollowing equation.CH3CH2COOH + CH3CH2OH CH3CH2COOCH2CH3 + H2O ΔH = –22 kJ mol–1The equilibrium mixture contained 0.54 mol of the ester ethyl propanoate.

Calculate moles of ethanol, propanoic acid and water. I dont get why the moles of water formed is 5.54?? I thought 0.54 would be used up from the reactants but then also formed from the products giving 5 moles?
20. (Original post by AqsaMx)
A mixture was prepared using 1.00 mol of propanoic acid, 2.00 mol of ethanol and 5.00 molof water. At a given temperature, the mixture was left to reach equilibrium according to thefollowing equation.CH3CH2COOH + CH3CH2OH CH3CH2COOCH2CH3 + H2O ΔH = –22 kJ mol–1The equilibrium mixture contained 0.54 mol of the ester ethyl propanoate.

Calculate moles of ethanol, propanoic acid and water. I dont get why the moles of water formed is 5.54?? I thought 0.54 would be used up from the reactants but then also formed from the products giving 5 moles?
The water isn't used to produce the ester. 0.54 moles of the ester are produced, so an additional 0.54 moles of water are produced in the reaction, bringing the total amount of water in the equilibrium mixture up to 5.54 moles

Posted from TSR Mobile

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: September 26, 2016
Today on TSR

### Anxious about my Oxford offer

What should I do?

### US couple arrested - 13 children chained up

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Useful resources

Can you help? Study Help unanswered threadsStudy help rules and posting guidelines

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE