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Aqa chem 4/ chem 5 june 2016 thread

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Original post by Fibsy
For the Cl containing ketone and acyl chloride test, although both have a Cl so you would think both would form a white ppt with silver nitrate... is the haloalkane reactive enough to release the Cl?
Do you not have to release the halide first with aqueous NaOH for that to happen?

... just me trying to defend my pitiful case for 3 more marks

Posted from TSR Mobile


Yes, that is exactly what I put and it is right.

The RCH2Cl bond (C-Cl) is not polar enough without a strong base catalyst like NaOH. So, if you put "AgNO3" without NaOH, you will get full marks for white precipitate with the acyl chloride and no change with the RCH2Cl. If you put "AgNO3 with NaOH", CE=0.
Original post by Saldudsjen123
Omg that's what I put too! Literalist ly thought I was the only one,I mentioned it not being too strong a base so it doesn't denture your enzymes


thank god hahahaha, it sounds right but we'll have to wait and see
Original post by shirrushtii
i think this is the answer for the last question

Yup
Original post by emma_1111
Could we say that i2 wasnt included as it was a solid?


Not in rate determining step
Original post by MuaazAnsari
Yh you can


I put with ammonia misty fumes are given off is this wrong?
Does anyone else feel really let down? I have spent the past months revising hard and had done every past paper averaging about 84/85 so was really motivated to go and smash this and then AQA give us this horrendous paper... I think I've lost so many simple marks and now I feel really unmotivated to revise for CHEM5 because if they're this horrible again then anything I revise isn't going to come up :frown:
Chances of getting into uni are now very slim as I needed to average low As in both papers and think I've got low C/high D for CHEM4 :frown:
Original post by shiney101
Is anyone making a change.org petition?


I was literally on the website contemplating 🤔 We need a strong, balanced argument.
Original post by Fibsy
Is this for the acyl chloride and the ketone? I put silver nitrate too, but now I realise that there was a chlorine on both of them so silver nitrate would produce a white ppt with both :/

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there was a similar question on the jan 2007 paper, agno3, acycl chloride white ppt formed , vigorous. with the ch2cl one, could either say no visible change or slow white ppt formed
Hey what did everyone tick for the number of C peaks? was it 9?
Original post by shirrushtii
i think this is the answer for the last question


I thought there was a ch2-o-ch3 group
Reply 1430
Avatar for cowie
cowie
7
was there any question we had to say excess NH3? - can't remember where I put it.. I really hope i didn't put it after KCN in ethanolic solution as the next step was OBVIOUSLY H2/Ni (which I hope I put) and which I have gotten correct every time it has come up in past paper questions.. Mind goes loop-de-loop in exams ffs.
Original post by Medlad101
thank god hahahaha, it sounds right but we'll have to wait and see


Yeah hopefully there will be more than one option other than it being more soluble!!
alsooo you know the very first Q... i put ch3cooh +h2o ----> ch3coo- + h3o+
is that ok?
Original post by Cadherin
I can't see why not - it's the most valid method I've seen so far.

Besides, it was a unit 1 synoptic question and I think AQA were hinting at that by the way they asked the question.


Yeah, thats the only I thought was possible.. Did any others use empirical formula method??
Original post by emilies18
alsooo you know the very first Q... i put ch3cooh +h2o ----> ch3coo- + h3o+
is that ok?


yeah
Original post by emilies18
tests for acyl chloride- can you use sodium hydrogen carbonate?


I used Na2CO3 - No change with Ketone, Effervescence with acyl chloride
Original post by Jackmilne95
Hey what did everyone tick for the number of C peaks? was it 9?

Yeah I put 9 - there were 14 carbons but 5 were the same due to symmetry : C6H3(CH3)2-NH-CH2-C(O)-N-(CH3CH2)2
Original post by Cadherin
Yes, that is exactly what I put and it is right.

The RCH2Cl bond (C-Cl) is not polar enough without a strong base catalyst like NaOH. So, if you put "AgNO3" without NaOH, you will get full marks for white precipitate with the acyl chloride and no change with the RCH2Cl. If you put "AgNO3 with NaOH", CE=0.


Yass! That's the thinking I had too but afterwards nobody else put this so im glad I found this haha
Reply 1438
Avatar for Zaker
Zaker
Original post by Cadherin
It may be possible that they allow more than one answer (but not one with iodine) I would have thought. If lots of candidates offer alternatives (which is possible) and as long as you justify it properly, this may be the case.

Or M1 may be dependent on a properly explained M2.


does anyone remember the exact question for this?
What did everyone write for the question asking why is the initial rate of the reaction used?

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