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WJEC CH4 June 2010

How did everyone find it? I though it was alright but there were some really awful questions that noone i know seemed to get. Like the three HBr isomers, think it was the two chiral isomers and 1 bromo. Didnt get it in the exam though.... :rolleyes:

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Reply 1

doladoo

I thought it was pretty good, much nicer than the January paper. I couldn't believe there was no nmr spectroscopy or anything on it, such luck! I hate that.

For the 3 isomers i did Br and carbon 1, Br on carbon 2 and a Br on a methyl group on carbon 2. No idea if that's right.

Reply 2

nickyboy

Yooo, i did the same for the Isomers aswell, I thought it wasn't to bad either, was totally unprepared in the Jan exam but think ive done enough for a B maybe :smile:

Bit that got me was the end of question 5..I really had no clue ha.

Reply 3

doladoo

Same for me, I had a U in January but I think I definitely got a C if not a B today. (hope I haven't jinxed myself now haha)

I think I lost it a bit on question 5. I don't think I did the percentage yield part right, I got around 77% if I remember right.

Reply 4

SirAlexander

I sat this exam with the intention to get a higher module grade than what I had in January (A), I don't think did.

I think this exam was toooo synoptic; I hated it. :frown:

Reply 5

rabidmonkey

i did the same but i think the answer was: 1 bromo butane and then 2 bromobutan. As 2 bromobutane is chiral it counts as two. You can then check by shining polarised light through it. One spins it one way, one the other and one not at all.

Having said that in the actual exam i put the same as both of you. It took like 7 of us to figure it out afterwards.

And i got 77% too.

Reply 6

nickyboy

I think my value was wrong, it was all guesswork on that ha..But the benzene question was alright atleast :smile:

What did you put as the test for the Hbr isomers?? I think i put add naoh then lucas test but wasn't to sure

Reply 7

SirAlexander

rabidmonkey

Hm, I'm glad I had that.

In explaining how to distinguish them, I wrote that the two optically active ones rotate plane polarised light in opposite directions and to distinguish the final isomer, CH3CH2CH2CH2BR, I rambled about hydrolysing it with NaOH to change it to a primary alcohol and then oxidise it to an aldehyde and test for the aldehyde using Tollen's reagent.

Reply 8

doladoo

Pretty sure this is wrong but I put add naoh to make corresponding alcohols. then oxidise with acidifed potassium dichromate. the isomer with the Br on the methyl wont oxidise, so no colour change from orange to green. To distinguish between the others tollens or fehlings.

Reply 9

SirAlexander

doladoo

That's partly right, though I don't think there was a methyl group and also they want you to mention the chirality of the other two isomers.

What did everyone get for the question on the second page, about how many double bonds there were?

Reply 10

doladoo

Yeah it completely slipped my mind about optical isomers.
I put one of my isomers with a methyl group so maybe it'll get consecutive marks.

I put 3, I had no idea at all for that.

Reply 11

rabidmonkey

SirAlexander

I got 4 double bonds, one for each mol of H2.

Reply 12

Jade02

SirAlexander

I sat this exam with the intention to get a higher module grade than what I had in January (A), I don't think did.

I think this exam was toooo synoptic; I hated it. :frown:

someone else nutty enough to resit and A in CH4, I was thinking I'd have to check myself into a mental home. I thought it was horrible yet most seem to say ok :frown:

Reply 13

SirAlexander

rabidmonkey

I got 4 double bonds, one for each mol of H2.

How did you work out how many moles?

Reply 14

Lulzman

I didn't mind the big question on Benzene. 6 easy marks :smile:

Reply 15

SerotoninAddict

I thought that exam was quite nice :smile:

Much better than January anyway, which I was totally unprepared for :smile:

I got 4 doubles bonds too

For the test between ethylamine and phenylamine what did everyone put?
I think the answer was adding nitrous acid and ethylamine would produce ammonia gas which would turn red litmus blue?

I didn't put that in the exam though, I said to add nitrous acid to turn ethylamine into ethanol and then add potassium dichromate and there would be a colour change from orange to green?
Think I'll get that?

Reply 16

SirAlexander

Jade02

someone else nutty enough to resit and A in CH4, I was thinking I'd have to check myself into a mental home. I thought it was horrible yet most seem to say ok :frown:

I made so many stupid mistakes, mostly on the 1 mark questions. :mad:

Reply 17

SerotoninAddict

Lulzman

I didn't mind the big question on Benzene. 6 easy marks :smile:

Plus two QWC marks :wink:

Or was the 2 QWC included within the six? :frown:

Reply 18

SerotoninAddict

SirAlexander

How did you work out how many moles?

They said that one mole would be like 22.something dm3

And 22.something times 0.4 was the 8.96 or whatever it was that they gave you.

So it was 0.1 moles to 0.4 moles, which is 1 moles to 4 moles.

Thats how I did it anyway :smile:

Reply 19

SirAlexander

Ian80

I thought that exam was quite nice :smile: