Turn on thread page Beta
    Offline

    0
    ReputationRep:
    the reasons for the only very small difference on enthalpies of neutralisation is the fact that, whilst some heat energy must be absorbed to complete ionisation of ethanoic acid molecules, the ethanoate and hydrogen ions formed upon dissociation as a result of hydration by polar water molecules, involving the electrostatic attration of the water's dipole ends with the charged ions. Thus hydration i s an exothermic process and sol the dissociation process is made less endothermic than it would otherwise be
    Offline

    0
    ReputationRep:
    (Original post by mathemagician)
    (Original post by mackin boy)
    step 3 was hot alkaline KMnO4 (NaOH)
    it was the iodoform reaction
    It was hot alkaline (NaOH) KMnO4.
    Offline

    0
    ReputationRep:
    (Original post by mathemagician)
    (Original post by mackin boy)
    i sed iodine was the oxidising agent
    it was acidified potassium dichromate
    it was iodine.
    Offline

    1
    ReputationRep:
    it was iodine, im sure of it now. well, im telling myself that now.
    Offline

    1
    ReputationRep:
    it was iodine
    • Thread Starter
    Offline

    1
    ReputationRep:
    Pretty sure it's iodine but I put iodide ions :mad:
    Offline

    0
    ReputationRep:
    A few questions...

    What did you put for the definition of the rate constant? I said its the number by which the concentrations are multiplied to give the rate, in the rate equation :-\

    Also, for the test to prove there's iodine in CHI3, did you say that when you heat it with NaOH the yellow ppt disappears, and a yellow ppt forms when you add AgNO3 ? Or is there a better (more correct) way to test it?

    With Chemistry I'm always worried that the examiner will only skim through at and even if the answers are correct, if they don't see the key words they'll mark it wrong :-S
    Offline

    0
    ReputationRep:
    i put: the constant of proportionality in the rate equation
    i put the same test to find iodine in CHI3, as its just a funny halogenoalkane!!

    Well, although its biology, in their mark schemes, they put 'if the science is right, mark it right' or words to that effect
    Offline

    0
    ReputationRep:
    (Original post by anish1411)
    Humm.. I wrote Iodine because I thought Halogens = oxidising agents. But then I had a moment of genius mental clarity and changed it to OH- And then on the train home I was thinking about it, and I couldn't figure out WHY I DID THAT AHHH!!
    lol i did just the opposite. couldn't been better :rolleyes:
    Offline

    13
    (Original post by anish1411)
    It was hot alkaline (NaOH) KMnO4.

    there was also a question asking you to write out the iodoform reaction for 3 marks...this also gave the product:

    C6H5-COONa
    • Thread Starter
    Offline

    1
    ReputationRep:
    (Original post by Mathemagician)
    there was also a question asking you to write out the iodoform reaction for 3 marks...this also gave the product:

    C6H5-COONa
    I had memorised that equation as it'd come up in a past paper, great question for 3 marks.
    Offline

    2
    ReputationRep:
    What will be the grade boundries for this? Does any of you know a website or something to look it up?

    I think I've lost a lot of marks from unit 5. Can I catch up with unit 6??? Does any of you know whether we have to memorise the AS Level definitions for unit 6?
    Offline

    2
    ReputationRep:
    (Original post by kpg)
    Pretty sure it's iodine but I put iodide ions :mad:
    I did the same. Any chance they might give us a mark for I- ?
    • Thread Starter
    Offline

    1
    ReputationRep:
    (Original post by Goddess)
    I did the same. Any chance they might give us a mark for I- ?
    Depends how generous they are I guess but I'm doubting it to be honest! Not sure what the grade boundary will be like, most people I've talked to said the paper went ok so possibly will be a bit higher this time. I got 54/75 in a past paper and that was apparently an A so who knows..
    Offline

    0
    ReputationRep:
    (Original post by kpg)
    I had memorised that equation as it'd come up in a past paper, great question for 3 marks.
    Hopefully I got some marks, as I at least got the gist of it, and had triiodomethane as a product. I forgot that water is formed though, and put HI instead of H2O and I-
    Offline

    0
    ReputationRep:
    I- would definetely not get the mark- Iodide is a REDUCING AGENT only it CANNOT be reduced any further so its use as an oxidising agent is inconceivable
    • Thread Starter
    Offline

    1
    ReputationRep:
    (Original post by mr_shoe_uk)
    Hopefully I got some marks, as I at least got the gist of it, and had triiodomethane as a product. I forgot that water is formed though, and put HI instead of H2O and I-
    You definitley get a mark for triiodomethane as a product
 
 
 
Turn on thread page Beta
Updated: June 24, 2005
The home of Results and Clearing

3,398

people online now

1,567,000

students helped last year

University open days

  1. SAE Institute
    Animation, Audio, Film, Games, Music, Business, Web Further education
    Thu, 16 Aug '18
  2. Bournemouth University
    Clearing Open Day Undergraduate
    Fri, 17 Aug '18
  3. University of Bolton
    Undergraduate Open Day Undergraduate
    Fri, 17 Aug '18
Poll
Will you be tempted to trade up and get out of your firm offer on results day?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.