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

Reply 320

itsConnor_

11

Original post by Kamara7

Have you done it? How did you do if so? :redface:

Reply 321

alow

19

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.

Reply 322

itsConnor_

11

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

Reply 323

Professor L

14

Original post by itsConnor_

Have you done it? How did you do if so? :redface:

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 :facepalm:

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 :tongue:

I just didn't know what to do because the hydrogens weren't adding up :lol:

Other than that, it was... meh

Reply 324

rory58824

2

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.

Reply 325

thad33

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.

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

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Reply 326

alow

19

Original post by thad33

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

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It's not really that different.

Reply 327

ranz

5

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.

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Reply 328

rory58824

2

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.

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I print most of them.

Reply 329

thad33

12

Original post by alow

It's not really that different.

Of course it is. There's no pressure doing past papers.

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Reply 330

alow

19

Original post by thad33

Of course it is. There's no pressure doing past papers.

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If you're confident you've worked hard enough and revised effectively there should be no pressure in the exam.

Reply 331

AqsaMx

5

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?

Reply 332

pineneedles

14

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

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Reply 333

pineneedles

14

Original post by AqsaMx

Can anyone explain why CH3CH2COCl hydrolysed more readily than CH3CH2CH2Cl??

CH3CH2COCl has a carbonyl group, so the electronegative oxygen atom draws carbon's electrons away from it. This means that the carbocation of CH2CH2CH2Cl is less positive than that of CH3CH2COCl, therefore it is less attractive to nucleophiles, such as the oxygen atom of water in hydrolysis.

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Reply 334

pineneedles

14

Original post by AqsaMx

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??

It's redox because sodium loses an electron (and is oxidised) and the proton of the OH group of phenol gains an electron and is reduced to hydrogen.
2CH6H5OH +2Na > 2CH6H5O-Na+ + H2

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Reply 335

AqsaMx

5

Can anyone explain y u would multiply the concentration by 100?? In the last question

Reply 336

AqsaMx

5

Original post by pineneedles

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

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Oh I see, what's the water used for then?