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    How did you people find it? I think it was quite easy apart of that question on solutions A and B. Why B is not a buffer :confused: .
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    I found it quite hard, especially parts of question 4. For the A and B buffer question I said that B wasn't a buffer because the NaOH concentration was twice as concentrated as A, which affects its dissociation. couldn't think of much else!
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    for part of question 4 what did every one get for the percentage, and what was the chemcial label, im pretty sure i got both of those wrong!
    Apart from that and a few little bits it was okay, actually that and a few little bits is quite a lot, its only out of 60! arghhhhh
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    i could not do that qu AT ALL!!! meeesch: that answer seems sensible so i wouldnt worry about it too much!! i just left it out...

    why were there soooo many HARD calculations?!!!!! what was with the water of crysallisation thing?? and balancing the equation....

    i got 77.1 %
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    I got 77% and Cu(NO2)2 .3H20 for the label
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    The water of crystalisation think was needed to write the label part, it was not required for calculation bit
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    yep, got them 2 wrong...
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    I got 77% and Cu(NO2)2 .3H20 for the label
    thats what i got.

    And did anyone balance that equation it was soo hard to do i spent 15 mins on those 3 marks alone.
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    (Original post by dreamer86)
    yep, got them 2 wrong...
    no worries! i got the lot wrong probs :p:
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    And did anyone balance that equation it was soo hard to do i spent 15 mins on those 3 marks alone.
    Just step by step thing.
    Cu changed oxidation state from 0 to 2, nitrogen from 5 to 2. You write to half equqtions, balance those with H+ and H2o and then add them up. One minute job.
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    Yeh, I hated the last question, grrr! What was the gas in experiment 3 of the last question??
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    SO2
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    (Original post by belis)
    SO2
    belis rox :-p! i got all those oxidation state changes belis! but not the equation! think ill get a mark?
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    I came out thinking it was easy. But then after I was talking to people I realised how many I've probably done wrong - especially the easy ones strangely. Anyway, fortunately that was only half of one module, and the practical went ok. Plus there were some easy qus like what is the rate determining step etc...and I thought the last few questions were ok. fingers crossed its a b.
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    I found it quite hard, especially parts of question 4. For the A and B buffer question I said that B wasn't a buffer because the NaOH concentration was twice as concentrated as A, which affects its dissociation. couldn't think of much else!
    I think B wasn't a buffer because all of the acid would have reacted with the base because they were is 1:1 molar ratio. Therefore, the only species present in the solution would have been the salt, so if any base was added there would be no acid to 'mop it up', therefore the would be an increase in pH, so the solution wasn't acting as a buffer as it wasn't minimising change in pH.

    However, in solution A there would have been acid present too because there was double the amount of acid: base. So it could act as a buffer.

    Anyone else agree?
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    i got all those oxidation state changes belis! but not the equation! think ill get a mark?
    I think you will get 2 out of 3 marks if you got the oxidation numbers. Aspecialy if you have writen half equations right.

    I agree with Jan05 by the way. What a pity I did it totaly wrong in the exam lol.
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    (Original post by Jen05)
    I think B wasn't a buffer because all of the acid would have reacted with the base because they were is 1:1 molar ratio. Therefore, the only species present in the solution would have been the salt, so if any base was added there would be no acid to 'mop it up', therefore the would be an increase in pH, so the solution wasn't acting as a buffer as it wasn't minimising change in pH.

    However, in solution A there would have been acid present too because there was double the amount of acid: base. So it could act as a buffer.

    Anyone else agree?
    sensible suggestion! i found that Q odd!
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    (Original post by belis)
    SO2
    :eek: I wrote that. And then.. crossed it out
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    (Original post by violet)
    :eek: I wrote that. And then.. crossed it out
    for what? :confused: i hope you dont say nothing! and add me to msn haha :p: mean! i gave my address in ya PM's

    belis: i didnt write half eq's...

    but i wrote the reaction out showing the increase/decrease in ox numbers to exactly what you said!
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    I wrote that. And then.. crossed it out
    Never cross things out. First thought is always the best one. What did you write then instead of SO2?
 
 
 
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