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

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Original post by Kvothe the arcane
I put saturated

But was nervous as the following questions were about it.


I put saturated as well but I didn't describe it. I just said Stearic acid as it as a saturated fat. Would I get the mark?
i got propanoic acid as well
Original post by jadder1224
1465919140947-1446831368.jpg did anyone get these ?


Got something like that except I got ethanoic acid instead of propanoic acid. 60 was the Mr

COOH Mr is 45 so there is 15 as remaining which is CH3

Am I right?

Unless I calculated the Mr wrong :frown:
(edited 7 years ago)
Original post by four4
If you get the compound F wrong, but were able to to do all the other compounds with ecf marks, how many marks out of 7 would you get?


I think 4 or more out of 7, each of the structures were probably one mark, the carboxylic acid was unrelated so one mark for that, one ECF mark for the ketone, one ECF mark for the ester, and one mark (or more) for the explanation. That's just my guess though
Original post by jadder1224
1465919140947-1446831368.jpg did anyone get these ?


That's exactly what I got, and i'm pretty sure what a lot of people got too, so as long as your reasoning for H was good, 7/7 :biggrin:
Original post by ShannonD_1697
I got something like that too I think! Everyone else seems to have got 2.66g but I have no clue how! Can anyone explain how they did it?


You must have mixed up the actual and theoretical values. I made that mistake in unit 2 last year so it was definitely not happening again
Original post by TheDimpleboy
Think I'm the only that got 2.56 for the mass where you were given the percentage yield lol, looks like the right answer is 2.66. I must have made an mr error but hopefully I'll still get 2 working marks.

Also I said Kevlar for the polyamide question, but I don't think I'll get the mark, clothing fibres is what I should have put.

Other than that; the paper was a lot nicer than last years.


Weird, I got 2.56 at first, but then realised I'd made an error calculating the Mr of the product so I recalculated and got 2.66.. Sorry😁 Lets hope for ecf
Original post by MrKmas508
Is displayed formula okay?


Yeh. They should allow all kinds. I did it displayed too. It's just on my phone I have to draw it skeletaly
Reply 1928
Avatar for Amy322
Amy322
for this question on compounds h f g ... did you have to draw out skeletal
Reply 1929
Avatar for lanah_
lanah_
Is there an unofficial mark scheme?
Original post by Amy322
for this question on compounds h f g ... did you have to draw out skeletal


No, any formula showing the structure is fine.
Original post by ShannonD_1697
I got something like that too I think! Everyone else seems to have got 2.66g but I have no clue how! Can anyone explain how they did it?


Mass of the reagent was 3g, with a Mr of 93.
So mass / molar mass is 3/93 = 0.03225... So that's how many moles we had
Percentage yield was 61% so the above x0.61 is 0.19677...moles were formed
Multiply that by the molar mass of the product (135 I think it was?) and you get 2.66g
Original post by sakuraton
Got something like except I got ethanoic acid instead of propanoic acid. 60 was the Mr

COOH Mr is 45 so there is 15 as remaining which is CH3

Am I right?


Had Mr as 74

Think it was 22.8/1000 x 0.125 for the moles then 0.211 over that answer games 74. 0something


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Original post by sakuraton
Got something like except I got ethanoic acid instead of propanoic acid. 60 was the Mr

COOH Mr is 45 so there is 15 as remaining which is CH3

Am I right?


The MR was 74... the molecular ion peak was at 74. Relative mass of carboxyl group is 45. 74-45= 29, which obviously indicates a CH3CH2-R group, so yeah, it's definitely propanoic acid, sorry :/

Edit: just had a brain fart, you had to calculate 74 using the values for reaction between C.A. and NaOH :tongue:
(edited 7 years ago)
Original post by FluffyCommie
The MR was 74... the molecular ion peak was at 74. Relative mass of carboxyl group is 45. 74-45= 29, which obviously indicates a CH3CH2-R group, so yeah, it's definitely propanoic acid, sorry :/


Okay then, I don't know how I got 60 as Mr whoops
Original post by greenorange
I put 1.2 ppm
2.6 ppm
3.6 ppm


It was all under 2 I thought. As it was a 3 Carbons. Doublet, Doublet, Multiplet
I said nylon used in rope not clothing, technically I'm right but would they give the mark :/
Original post by grannyG
Lactic acid has a chiral carbon, meaning chemical synthesis produces optical isomers whereas biological synthesis (fermentation) doesn't

Did you also state the number of possible isomers (2)? They wanted to see the actual number of possibilities in the Jun15 paper.
Original post by sakuraton
Got something like that except I got ethanoic acid instead of propanoic acid. 60 was the Mr

COOH Mr is 45 so there is 15 as remaining which is CH3

Am I right?

Unless I calculated the Mr wrong :frown:


I got the Mr as 74 hence proanoic acid
Original post by ShannonD_1697
I got something like that too I think! Everyone else seems to have got 2.66g but I have no clue how! Can anyone explain how they did it?


I got 2.66g - I did it by working out the moles of Phenylamine (which came to 0.03something), then did:

61% = A/0.03something x 100

Rearranging gave the moles of A as 0.01something, which I then multiplied by 135 to get 2.66g.

The logic I used was that we started with 3g of reagent so we couldn't possibly have 7+g of product because that's more than 3g!

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