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AQA CHEM2 ~ May 23rd 2012 ~ AS Chemistry

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Original post by Mocking_bird
I was just making a comparison to the different types of nucleophillic substitution.

& No, but I would like high UMS. :smile:


All you need to do is remember that CN is the only type of nucleophillic substitution that results in a longer carbon chain.

Of course. :smile:

I expect you to continue working hard next year anyway though, and so higher UMS on this unit won't make a jot of difference to your overall grade.
Original post by IchHabDichLieb
can someone help me out...why is 8a (i) NaCl and not NaBr if a cream ppt is formed:confused:



Original post by Mocking_bird
It was a horrible question..
Basically, because you have 2 sodium halides in the same solution and it makes a cream ppt, it must be AgI (yellow) and AgCl (white), because AgBr (already cream) and AgI would just make a yellow-y colour ppt still.



Actually I thought it was because the colour changed after adding dilute ammonia, and NaBr doesn't dissove in dilute ammonia, so it must be NaCl which does dissolve?

Agreed though, horrible question
Original post by TaraBelle
Actually I thought it was because the colour changed after adding dilute ammonia, and NaBr doesn't dissove in dilute ammonia, so it must be NaCl which does dissolve?

Agreed though, horrible question


NaBr is slightly soluble.

:dontknow:
The way I said is the way my chem teacher explained it.
Original post by Mocking_bird
NaBr is slightly soluble.

:dontknow:
The way I said is the way my chem teacher explained it.


and I said what my teacher told me too haha :L but would it be soluble enough for the colour to change that much? :/
Is it national **** day on TSR today?

Edit: he deleted his post, i wasnt saying that to you Tara :tongue:
(edited 11 years ago)
i was under the impression that AgBr dissolved in dilute ammonia but AgI doesnt. AgI requires concentrated ammonia to dissolve? could be wrong though, if so please someone point it out lol .
Original post by cuckoo99
i was under the impression that AgBr dissolved in dilute ammonia but AgI doesnt. AgI requires concentrated ammonia to dissolve? could be wrong though, if so please someone point it out lol .


This isn't quite right.
AgCl - dissolves in dilute ammonia
AgBr - dissolves in conc ammonia
AgI - does not dissolve in ammonia
Reply 667
Avatar for erniiee
erniiee
13
Hey does anyone have the Jan 12 mark scheme for Chem2?
does anyone have anything on analytical techniques? i dont really get it...
Original post by cheesecake11
does anyone have anything on analytical techniques? i dont really get it...


http://www.a-levelchemistry.co.uk/AQA%20Chemistry/AQA%20AS%20Chemistry/Unit%202/2.11%20Analytical%20Techniques/2.11%20Analytical%20Techniques%20home.htm

Original post by erniiee
Hey does anyone have the Jan 12 mark scheme for Chem2?


http://www.thestudentroom.co.uk/showthread.php?t=1960030

Tullias post :smile:
Original post by Mocking_bird


thanks!
Original post by clownfish
This isn't quite right.
AgCl - dissolves in dilute ammonia
AgBr - dissolves in conc ammonia
AgI - does not dissolve in ammonia


ah thank you :smile: i've been poor at the halogen experiments :/
Original post by Tullia
All you need to do is remember that CN is the only type of nucleophillic substitution that results in a longer carbon chain.

Of course. :smile:

I expect you to continue working hard next year anyway though, and so higher UMS on this unit won't make a jot of difference to your overall grade.


interesting, thanks for this :smile: now when it comes to naming nitriles i wont balls it up. That is if it even comes up ;p
Anyone want to start asking each other questions? :dontknow:
Do we need to know anything about fragmentation (last topic)
other than what it is?
Original post by Mocking_bird
Anyone want to start asking each other questions? :dontknow:


give 1 way how you can increase the yield of ammonia in the habar process. Explain your answer:
Reply 676
Avatar for erniiee
erniiee
13
Original post by Mocking_bird


Thanks :biggrin:
Original post by cuckoo99
give 1 way how you can increase the yield of ammonia in the habar process. Explain your answer:

Spoiler



Some questions:
1. Why is it not favourable to use Hydrogen as a reducing agent in metal extraction?
2. What is roasting (when referring to metal extraction)
3. What effect does a catalyst have on a reaction at dynamic equilibrium
4. What type of alcohol is butan-2-ol
5. What is a hydroxide ion acting as in a elimination reaction?
Original post by cuckoo99
give 1 way how you can increase the yield of ammonia in the habar process. Explain your answer:


Spoiler



Original post by Spellstheend

Spoiler



Some questions:
1. Why is it not favourable to use Hydrogen as a reducing agent in metal extraction?
2. What is roasting (when referring to metal extraction)
3. What effect does a catalyst have on a reaction at dynamic equilibrium
4. What type of alcohol is butan-2-ol
5. What is a hydroxide ion acting as in a elimination reaction?


Spoiler



Q's:
1)What is the test for sulfate ions?
2)When alkenes join up what kind of polymers do they form?
3)How do you ensure you make a carboxylic acid instead of an aldehyde?
4) State Le Chateliers principle
5) What effect does adding a catalyst have on most probable energy level?
Original post by Spellstheend

Spoiler



Some questions:
1. Why is it not favourable to use Hydrogen as a reducing agent in metal extraction?
2. What is roasting (when referring to metal extraction)
3. What effect does a catalyst have on a reaction at dynamic equilibrium
4. What type of alcohol is butan-2-ol
5. What is a hydroxide ion acting as in a elimination reaction?


Spoiler

(edited 11 years ago)

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