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    (Original post by BackDoorEntry)
    In the exam it asked us for something, and all the arrows were pointing downwards. So you had to reverse the enthalpy change of solution so its arrow was pointing upwards I think, I can't remember the paper.

    But yeah everything below 'Breakdown of the ionic lattice' and the next page kinda suggests the relationship between all three enthalpy changes, so in the exam they were asking you to apply this.
    ah well...I just subbed in some numbers, hit a few buttons on my calc, got a number and wrote it down

    and I pretty much used this method for most of the questions on the paper
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    (Original post by viksta1000)
    Ok, tbf i actually agree with u with the fact it covered most topics

    But where on the syllabus does it teach you to apply chemistry in the way they applied it in the exam paper?

    E.g negative enthalpy change of solution? Recharging cells? Buffer ratios?

    Theres not a single question, spread, paragraph or even a sentence that teaches you to apply these topics in the way they asked in the exam

    Its not long before you add up the marks for these sort of question and find youve lost 20+ marks
    Completely agree with you... revised so hard for this exam did loadsa pass papers revised everything on spec and know without a doubt ive dropped over 20marks .. OCR better drop the boundaries
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    (Original post by peace345)
    Completely agree with you... revised so hard for this exam did loadsa pass papers revised everything on spec and know without a doubt ive dropped over 20marks .. OCR better drop the boundaries
    exactly, same here...worked my ass off all year to get to the point where I needed around 100 ums (about 65%) on this exam...and I honestly think I've flunked it due to the crappy paper
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    (Original post by Rosi M)
    Anybody resitting F324 on Friday like me? Any predictions
    I am! My whole class is lol we ****ed up
    How you feeling about it?
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    Guys the lowest the grade boundaries can be is 65/100 for an A full stop!!! We had the same issue in January when we said the F324 paper was really hard. We thought that they will lower the boundaries where in fact they made them higher because I june 2010 for an A it was 41/60 whereas in Jan 2011 it was 44/60. Let's just hope that they will keep the boundary to 65/100. I also struggled with the paper am just hoping that I'll get an A.
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    To all those complaining about the magic tang question, it really wasn't that difficult.

    There's an example in the OCR textbook (question 9c on page 159) about calculating the ratio of acid/salt needed to form a buffer at a particular pH.

    And on page 153 of the same textbook, the stretch/challenge box explains how the pH of a buffer is equal to the pKa of the acid when the acid exists in a 1:1 ratio with its salt. And then it explains that by altering the ratio from 1:10 to 10:1 you can change the pH +1 or -1. Hence you should initially choose an acid with a pKa close to the required pH and then fine-tune the ratio to get the required pH.

    Once again, the majority of candidates have failed to learn the whole syllabus and then complain at questions they can't answer. Jeez.
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    (Original post by BA1)
    To all those complaining about the magic tang question, it really wasn't that difficult.

    There's an example in the OCR textbook (question 9c on page 159) about calculating the ratio of acid/salt needed to form a buffer at a particular pH.

    And on page 153 of the same textbook, the stretch/challenge box explains how the pH of a buffer is equal to the pKa of the acid when the acid exists in a 1:1 ratio with its salt. And then it explains that by altering the ratio from 1:10 to 10:1 you can change the pH +1 or -1. Hence you should initially choose an acid with a pKa close to the required pH and then fine-tune the ratio to get the required pH.

    Once again, the majority of candidates have failed to learn the whole syllabus and then complain at questions they can't answer. Jeez.
    Finally someone who isn't just out there to have a go at the exam boards. I love the way that as time progresses there is less and less for people to claim thats theres stuff not in the book.
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    (Original post by viksta1000)
    true, but even if they threw just one example in the book, just to give me a heads up, then I wouldn't be bothered

    my main concern was that the paper was predominantly application/stretch and challenge, rather than just a couple of questions

    we'll have to wait until august I guess...hopefully OCR haven't sabotaged my university chances
    This is what my chemistry teacher said. I thought it was fine except for magic tang question but he said that it was fine for those who could do stretch and challenge as most of it did consist of that.
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    (Original post by BA1)
    To all those complaining about the magic tang question, it really wasn't that difficult.

    There's an example in the OCR textbook (question 9c on page 159) about calculating the ratio of acid/salt needed to form a buffer at a particular pH.

    And on page 153 of the same textbook, the stretch/challenge box explains how the pH of a buffer is equal to the pKa of the acid when the acid exists in a 1:1 ratio with its salt. And then it explains that by altering the ratio from 1:10 to 10:1 you can change the pH +1 or -1. Hence you should initially choose an acid with a pKa close to the required pH and then fine-tune the ratio to get the required pH.

    Once again, the majority of candidates have failed to learn the whole syllabus and then complain at questions they can't answer. Jeez.
    Totally agree with you. I personally could not do the magic tang question, but I hadn't done that question in the book, so it was my fault. Everything else in that paper, regardless of whether I could do it or not, I saw in the book, so I agree. If I didn't get the grade I need, I only have myself to blame.
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    (Original post by PhilliChilli)
    I am! My whole class is lol we ****ed up
    How you feeling about it?
    Ah im really scared and we just need to accept the fact that it will be a WIERD paper with WIERD questions.. :eek: Im scared 'cos i tried really hard in Jan, did well in all past papers then got a D.. so im worries it may happen again! In terms of revision, im just going through NMR right now then got pile of papers to get through. Welcome all nighter.
    How about you?
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    I guess they think it's the best way to do the exams, but I do wish they'd give us more time and then up the boundaries. If I had the time to give a decent shot at all the questions I'd feel so much more like it was a fair chance. When you know when you're in that exam that you're never going to have enough time to get through the questions, and you leave having missed out a load of questions, it just makes you feel so so **** but then I do admit I'm not the best at chemistry.
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    my chemistry teacher said it was the hardest exam hes seen in 20 years so all those who say it wasn't that hard, stop talking out your backside, get down from your high horse and accept it was a difficult paper. Btw i was on an A going into that exam and am resigned to the fact i know i got a D in this paper
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    (Original post by Rosi M)
    Ah im really scared and we just need to accept the fact that it will be a WIERD paper with WIERD questions.. :eek: Im scared 'cos i tried really hard in Jan, did well in all past papers then got a D.. so im worries it may happen again! In terms of revision, im just going through NMR right now then got pile of papers to get through. Welcome all nighter.
    How about you?
    omg you aswel! Haha ill have to quote you a lot on ere during my all nighter tonight then I SUCK at analysis im literally just doing all of those questions that i can find. :/
    oh dear....:awesome: i have a feeling theres gonna be a lot of lines in this exam oh no! :eek:
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    (Original post by BA1)
    To all those complaining about the magic tang question, it really wasn't that difficult.

    There's an example in the OCR textbook (question 9c on page 159) about calculating the ratio of acid/salt needed to form a buffer at a particular pH.

    And on page 153 of the same textbook, the stretch/challenge box explains how the pH of a buffer is equal to the pKa of the acid when the acid exists in a 1:1 ratio with its salt. And then it explains that by altering the ratio from 1:10 to 10:1 you can change the pH +1 or -1. Hence you should initially choose an acid with a pKa close to the required pH and then fine-tune the ratio to get the required pH.

    Once again, the majority of candidates have failed to learn the whole syllabus and then complain at questions they can't answer. Jeez.
    I could do the stupid buffer calculation, it's the irrelevant trivia part at the end that annoyed me about that question.
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    (Original post by Unkempt_One)
    I could do the stupid buffer calculation, it's the irrelevant trivia part at the end that annoyed me about that question.
    how did you do it ?
    I chose the weak acid
    and from it's pka
    I calculated Ka.
    then I did

    concentration of acid = (ph required)^2 / ka ( of the weak acid I chose)

    then I used the concentration of the acid
    to find the conc of salt.

    IS that right ?
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    (Original post by RodrigoB)
    how did you do it ?
    I chose the weak acid
    and from it's pka
    I calculated Ka.
    then I did

    concentration of acid = (ph required)^2 / ka ( of the weak acid I chose)

    then I used the concentration of the acid
    to find the conc of salt.

    IS that right ?
    I can't remember the full details of the question, but I got 0.49 for my ratio. I think it was something like use the full expression for Ka (not the simplified one you use for pH calculations) and the ratio is equal to Ka/required concentration of H+.
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    (Original post by Unkempt_One)
    I can't remember the full details of the question, but I got 0.49 for my ratio. I think it was something like use the full expression for Ka (not the simplified one you use for pH calculations) and the ratio is equal to Ka/required concentration of H+.
    god I knew how to calculate the ratio ratio but
    I ended up calculating the ACID and SALT conc !
    I thought that this was what they were asking me to do no ?
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    The paper was fair, the crap before the questions makes the amount of time we get unfair.
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    (Original post by RodrigoB)
    god I knew how to calculate the ratio ratio but
    I ended up calculating the ACID and SALT conc !
    I thought that this was what they were asking me to do no ?
    Sorry dude, I don't think so.
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    This is annoying me now. It was a hard paper, yes, but it was the final paper of the chemistry A2 so it's to be expected, especially when the examiners warned that there would be a pressing time limit and harder questions to differentiate at the top. Get over it, everyone sat the same exam, and the grade boundaries will be adjusted accordingly, whether that be up or down. It is not a conspiracy against you all, so you can take off your tin foil hats. Rant over...

    (Original post by viksta1000)
    true, but even if they threw just one example in the book, just to give me a heads up, then I wouldn't be bothered
    The thing is I'm fairly sure you're entirely missing the point, the stretch and challenge questions were there to make you think, not to remember, that's the entire point. There were past papers and similarly styled questions in the book, so you have nothing really to complain about.
 
 
 
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