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Chemistry AQA CHM4 (old spec) post exam discussion watch

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    was it just me or where there two questions asking for the mechanism of electrophillic substitution- one for nitro benzene the one using an acyl chloride (AlCl3 as the catalyst)
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    (Original post by frosty25)
    anyone get [A]- = 0.50 mol.dm-3??? on the acid dissociation question
    I think I got something else but I cant remember to be honest. I must be wrong because I worked it out in a weird way. I converted the PH given into [H+] and used [HA] value and Ka given in the question and rearranged it to work out [A-]. I'm not sure if that was what you were meant to do lol.

    I think you probably had to convert PH into [H+] and use Kw to work it out.

    So I might have it wrong. Great.
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    (Original post by silva228)
    was it just me or where there two questions asking for the mechanism of electrophillic substitution- one for nitro benzene the one using an acyl chloride (AlCl3 as the catalyst)
    You're right. There were two.

    One was benzene with NO2 with a + on the N
    One was benzene with CH3CO with a + on the middle C

    Do you remember what you got for the organic products?

    I think I got N-ethylethanamide and Phenylethanone Or something like that.
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    (Original post by zaf1991)
    I think I got something else but I cant remember to be honest. I must be wrong because I worked it out in a weird way. I converted the PH given into [H+] and used [HA] value and Ka given in the question and rearranged it to work out [A-]. I'm not sure if that was what you were meant to do lol.

    I think you probably had to convert PH into [H+] and use Kw to work it out.

    So I might have it wrong. Great.
    No mate I worked it out like this as well, buffer calculations always seem to use a rearrangement of Ka which is what this was I tihnk- I didnt get 0.50 but I might be wrong :confused:
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    HOLD ON!!! QUESTION TEN??? IM SURE ILOOKED BACK AND THERE WAS NO QUESTION TEN!!! im freaking out right now, please get back to mee soon!!!!
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    (Original post by silva228)
    No mate I worked it out like this as well, buffer calculations always seem to use a rearrangement of Ka which is what this was I tihnk- I didnt get 0.50 but I might be wrong :confused:
    Well we definitely used the correct method then. We should get the marks, god willing. provided we don't have mathematical errors obviously.
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    (Original post by SomeStudent)
    HOLD ON!!! QUESTION TEN??? IM SURE ILOOKED BACK AND THERE WAS NO QUESTION TEN!!! im freaking out right now, please get back to mee soon!!!!
    Chillax. It was a joke someone played. lol.
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    (Original post by mlo90)
    Oooo zaf1991 or shall I say sherlock lol!

    There wasn't a question 10 just wanted to see how long I could convince that there was one
    oh my god I almost had a minor heart attack... I'm not even joking, my head felt so dizzy after reading your posts :p:
    huusaaaah... don't do that again! :p:
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    lol. I almost went into a panic attack too.
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    (Original post by zaf1991)
    You're right. There were two.

    One was benzene with NO2 with a + on the N
    One was benzene with CH3CO with a + on the middle C

    Do you remember what you got for the organic products?

    I think I got N-ethylethanamide and Phenylethanone Or something like that.
    yh i got the exact same...
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    (Original post by zaf1991)
    You're right. There were two.

    One was benzene with NO2 with a + on the N
    One was benzene with CH3CO with a + on the middle C

    Do you remember what you got for the organic products?

    I think I got N-ethylethanamide and Phenylethanone Or something like that.
    I wrote n ethyethanamine ... and for the other one phenylethanoate - i knew it wasn't an ester, but phenylethanone sounded weird :|
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    (Original post by zaf1991)
    I think I got something else but I cant remember to be honest. I must be wrong because I worked it out in a weird way. I converted the PH given into [H+] and used [HA] value and Ka given in the question and rearranged it to work out [A-]. I'm not sure if that was what you were meant to do lol.

    I think you probably had to convert PH into [H+] and use Kw to work it out.

    So I might have it wrong. Great.
    i think the equation went:

    [A-]= (Ka x HA) /[H+]

    i worked out H+ via antilog
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    (Original post by SomeStudent)
    I wrote n ethyethanamine ... and for the other one phenylethanoate - i knew it wasn't an ester, but phenylethanone sounded weird :|

    what did you get for the simple test tube reactions?
    the ones with aldehyde + carbon and ketone + carboxylic acid?
    WHAT?!?!?

    I thought one was an alcohol and the other was an aldehyde

    and the other was an Ester and the other was a carboxylic acid??

    OMG
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    I got the feeling grade boundaries will be higher than they have ever been before. The highest I have seen is 73 for an A. I was getting 73's at home lol.
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    (Original post by Circularmover)
    i think the equation went:

    [A-]= (Ka x HA) /[H+]

    i worked out H+ via antilog
    Yeah dude. I did the same.
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    (Original post by zaf1991)
    Yeah dude. I did the same.
    ur applyin for optom? whats ur stats?
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    (Original post by SomeStudent)
    I wrote n ethyethanamine ... and for the other one phenylethanoate - i knew it wasn't an ester, but phenylethanone sounded weird :|

    what did you get for the simple test tube reactions?
    the ones with aldehyde + carbon and ketone + carboxylic acid?
    Again I got the same as zaff, if an N has a group attached to it with a C=O i think its an amide.

    With the test tube reactions the aldehyde one I said Tollen reageant- silver mirror

    The one with the carboxylic acid in the next question (and I thought the other was an ester btw but it was irrelevant if you used the reageant I did) I used NaHCO3 and said the carboxylic acid gave effervesence
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    (Original post by Circularmover)
    WHAT?!?!?

    I thought one was an alcohol and the other was an aldehyde

    and the other was an Ester and the other was a carboxylic acid??

    OMG
    It was a secondary alcohol so I assumed you could not use acidified potassium dichromate. So I said Fehlings lol.

    For the carboxylic acid one I said NaHCO3 - Effervescence (even though I think I spelt it wrong on the paper lol) of CO2
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    (Original post by Circularmover)
    WHAT?!?!?

    I thought one was an alcohol and the other was an aldehyde

    and the other was an Ester and the other was a carboxylic acid??

    OMG
    lol, I don't even know what I'm writing (Carbon???) Yeah, that's is what it was... sorry :o:
    what did you get?
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    (Original post by Circularmover)
    ur applyin for optom? whats ur stats?
    Nothing special.

    I'm on ABB... 1 UMS off an A in Chem lol

    I'm doing work experience in a opthalmic surgery this year. I didnt apply for 2009 because I messed my AS up bad... Had some severe personal problems... and thought I was not going to get good grades last year either but I didnt do that bad. . I like module 4 so I did it again. Plus I hope it will get me in the mood for the beast - CHM5.
 
 
 
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