Hey there! Sign in to join this conversationNew here? Join for free

Edexcel A2 Chemistry Exams -6CH04 (14th June) and 6CH05 (22nd June) Discussion Thread Watch

    Offline

    3
    ReputationRep:
    (Original post by narcotica)
    I wasn't expecting some of the multiple choice questions and the first mass spectrum question about naming 2 different ions. I had 20 mins extra to check over the paper but I had to waste that time trying to guess those multiple choice questions. Did you manage to find an unofficial mark scheme btw?
    Which multiple choice questions in particular did you not expect? I assume those are the same ones which you had to guess? No I haven't looked for an unofficial mark scheme. Are you retaking unit 2?
    Offline

    2
    ReputationRep:
    (Original post by sabahshahed294)
    Yes, you'll find them here.
    https://56leomessiphotoshop.blogspot...materials.html

    Thank you so much
    Offline

    10
    ReputationRep:
    (Original post by dpoojaraa)
    Which multiple choice questions in particular did you not expect? I assume those are the same ones which you had to guess? No I haven't looked for an unofficial mark scheme. Are you retaking unit 2?
    I only remember two now. One was which molecule has the same empirical and molecular formula, and the other one asked for the volume of gas produced in the reaction they gave but they only gave the volume of the reactants. Yeah, I did have to guess. I can't find one anywhere. Nope, I'm not retaking unit 2.
    Offline

    12
    ReputationRep:
    (Original post by ayvaak)
    Thank you so much
    Np.
    Offline

    12
    ReputationRep:
    Hi. I have two questions from Unit 4. It would be helpful if you can answer them.

    1-In a Reaction Profile Diagram for Multi Step reactions, it is said that the intermediate formed has a greater activation energy than the products. What makes it greater actually? Is it something to do with stability of the intermediate?
    2-In a Pseudo Zero Partial Order reaction, what's the main concept behind it? Is it assumed to be a reaction which has a reaction order of zero?
    • Thread Starter
    Offline

    10
    ReputationRep:
    (Original post by Funky_Giraffe)
    Hey guys, I've got a couple of multiple choice queries -

    this first one, I guessed right as D but I have no idea why it couldn't be some of the others... what are you supposed to look at? number of shared pairs or something...?? tbh I have no idea

    then for the second question, is there a rule about how to determine how fast a pair of compounds will react to form the polymer? (ans is B)

    thanks guys!

    Attachment 540983Attachment 540983540985
    For the first one, you need to look at what the ox state of titanium would be in the compound - the structure of the titanium suggests that it is unlikely for it to form anything further than +4, as there are 4 electrons in the 4s and 3d. For part 2, we can either react a carboxylic and an amine or an acyl chloride and an amine. From unit 4 we know that acyl chlorides tend to be much more reactive than carboxylic acids so hence the polymer forms faster
    • Thread Starter
    Offline

    10
    ReputationRep:
    (Original post by sabahshahed294)
    Hi. I have two questions from Unit 4. It would be helpful if you can answer them.

    1-In a Reaction Profile Diagram for Multi Step reactions, it is said that the intermediate formed has a greater activation energy than the products. What makes it greater actually? Is it something to do with stability of the intermediate?
    2-In a Pseudo Zero Partial Order reaction, what's the main concept behind it? Is it assumed to be a reaction which has a reaction order of zero?
    Question 2 isn't something you need to worry about for the spec - from what I know I believe it typically happens for something like water, e.g. if the reaction takes place in aqueous solution and is first order wrt water, the water is going to be in such excess that the reaction takes place at the same rate the whole time anyway. The first one again isn't really on the spec, but is normally to do with the mechnism of the reaction - to form the intermediate is normally where a lot of bonds are broken whereas the second hump tends to be where the bonds start to be reformed
    • Thread Starter
    Offline

    10
    ReputationRep:
    (Original post by Funky_Giraffe)
    Thank you! By the way, an unrelated question but why can potassium manganate oxidise alkenes to diols, yet potassium dichromate, which is also an oxidising agent, cannot?
    I suspect it is because manganate is a much stronger oxidising agent than dichromate is
    Offline

    2
    ReputationRep:
    Name:  20160531_145150.jpg
Views: 114
Size:  502.6 KBcould someone please explain what they mean in the first purple box - I don't understand why the total Ecell value would be lowered by an increase in Zn2+
    • Thread Starter
    Offline

    10
    ReputationRep:
    (Original post by n2697)
    Name:  20160531_145150.jpg
Views: 114
Size:  502.6 KBcould someone please explain what they mean in the first purple box - I don't understand why the total Ecell value would be lowered by an increase in Zn2+
    Ecell is a measure of the equilibrium they show - the more negative the ecelll the more that species tends to form ions and release electrons. If we add zn2+ we shift the equilibrium back towards the Zn, meaning there are less electrons so since in a copper zinc cell the zinc electrode is the negative one if there are less electrons that electrode is less negative so the potential difference is smaller
    Offline

    2
    ReputationRep:
    But i thought that since the equilibrium shifts to the right when more Zn2+ is added, electron gain becomes easier(as more Zn2+ is combining with 2e-) so as electron gain becomes easier the value is more negative as it's getting reduced and so ecell value is more positive
    Offline

    3
    ReputationRep:
    Does anyone know how strict they are on awarding the QWC mark? Idk, the mark scheme mostly has two or three line answers for these
    Offline

    12
    ReputationRep:
    (Original post by samb1234)
    Question 2 isn't something you need to worry about for the spec - from what I know I believe it typically happens for something like water, e.g. if the reaction takes place in aqueous solution and is first order wrt water, the water is going to be in such excess that the reaction takes place at the same rate the whole time anyway. The first one again isn't really on the spec, but is normally to do with the mechnism of the reaction - to form the intermediate is normally where a lot of bonds are broken whereas the second hump tends to be where the bonds start to be reformed
    Oh okay! Thank you so much!
    Offline

    9
    ReputationRep:
    (Original post by Ayman!)
    Does anyone know how strict they are on awarding the QWC mark? Idk, the mark scheme mostly has two or three line answers for these
    I think it's literally just checking that you are using terms in the correct way and spelling them correctly, with clear and correct grammar and punctuation throughout. To be honest Edexcel don't take it as seriously as some of the other boards (where a separate mark is awarded for QWC). There is no standalone mark for QWC in Edexcel papers.
    • Thread Starter
    Offline

    10
    ReputationRep:
    (Original post by Ayman!)
    Does anyone know how strict they are on awarding the QWC mark? Idk, the mark scheme mostly has two or three line answers for these
    Probably not very. As long as you are using proper terms and aren't writing stuff like 'alcohols have a higher gasing point because they have hydrogen thingies' or similar than they probably aren't going to dock you any marks - I believe it is more about using proper scientific vocab rather than whether you have used 4 semi colons and an exclamation mark in your answer
    Offline

    2
    ReputationRep:
    Name:  Screen Shot 2016-06-01 at 6.41.37 PM.png
Views: 90
Size:  17.5 KBAttachment 541491541493Why is the cell potential the same for reactions with same overall equation?
    Attached Images
     
    Offline

    12
    ReputationRep:
    (Original post by tgygt)
    Name:  Screen Shot 2016-06-01 at 6.41.37 PM.png
Views: 90
Size:  17.5 KBAttachment 541491541493Why is the cell potential the same for reactions with same overall equation?

    I have the same question as you. Found out while studying..but I guess the type of reaction is same and maybe that's why Ecell is the same!
    Offline

    12
    ReputationRep:
    Hey! need some help in these MCQs please
    http://qualifications.pearson.com/co...e_20150610.pdf

    6(a)- How come the answer is D instead of B?
    6(b)-Not getting correct answer so just want to know my mistake here.
    12(c)-Why is the answer C? Shouldn't it be D?
    Offline

    2
    ReputationRep:
    Just out of curiosity how many chemistry past papers can people get through in a day? I would love to have done them all before the exam but I'm not sure theres enough time. Instead I might just tackle the tough ones. Any recommendations for difficult both Unit 5 and 4 past papers?
    • Thread Starter
    Offline

    10
    ReputationRep:
    (Original post by ayvaak)
    Just out of curiosity how many chemistry past papers can people get through in a day? I would love to have done them all before the exam but I'm not sure theres enough time. Instead I might just tackle the tough ones. Any recommendations for difficult both Unit 5 and 4 past papers?
    when i do papers usually 2 chem and 2 maths in a day
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Has a teacher ever helped you cheat?
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • 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.