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OCR A2 CHEMISTRY F324 and F325- 14th and 22nd June 2016- OFFICIAL THREAD watch

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    (Original post by pezhman)
    Number of mole of HNO2 was 0.04
    Number of mole of NaNO2 was 0.05
    0.05-0.04=0.01 [NO2-]
    [H+]= (Ka*0.04)/0.01
    -log [H+] =pH
    I don't remember the Ka
    why do you subtract 0.05-0.04? nothing is neutralised
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    (Original post by lai812matthew)
    same as what you do
    i'm confident that's the right thing; there was nothing neutralised; it was simply the case of mixing an acid and it's conjugate base.
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    (Original post by MilkFriend)
    Ok, thanks, So does that means 10.76 is more likely to be the right answer?
    I think so, but I mightve misread it.
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    (Original post by ThatPerson2)
    I think so, but I mightve misread it.

    prerty sue its 10.76 dont worry.
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    (Original post by lawlieto)
    why do you subtract 0.05-0.04? nothing is neutralised
    No you don't subtact.You just use 0.05 and 0.04.
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    What percentage of the exam was repeat questions and what percentage of questions needed guessing
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    (Original post by Bilal2015)
    Has anyone done the paper? Unofficial mark scheme?


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    What percentage of the exam was repeat questions and what percentage of questions needed guessing
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    (Original post by Slenderman)
    In comparion to 2015. Harder or easier? Am I retarded to think the grade boundaries will be 75 for an A?
    What percentage of the exam was repeat questions and what percentage of questions needed guessing
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    (Original post by Shakikila)
    What percentage of the exam was repeat questions and what percentage of questions needed guessing
    what do u mean by guessing
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    Any unofficial mark schemes?
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    (Original post by Dinasaurus)
    I just did this and I expected there to be more to it, the fact she filled the water up to 100.0, had no relevance?
    Its because you have the same number of moles in more volume of water because its been diluted so your concentration changes
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    Think 70/100 will be a B?
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    (Original post by MrZebraCookie)
    Think 70/100 will be a B?
    Very likely.
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    My sister took the exam yesterday and she looks anxious..I just want to know how much of the exam was repeated questions..how much are new questions..thanks
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    (Original post by pezhman)
    [H+]= square root of Kw at 60c
    [H+]= square root 9.313*10^-14
    [H+]= 3.05*10^-7
    -log 3.05*10^-7= 6.5
    Since 6.5<7 so pH 7 is alkaline
    hey i did exactly this is this right or?
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    (Original post by lai812matthew)
    what do u mean by guessing
    My sister took the exam yesterday and she looks anxious..I just want to know how much of the exam was repeated questions..how much are new questions..thanks
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    Did anyone use redox systems 6 and 7 in that 6 marker?
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    (Original post by Shakikila)
    My sister took the exam yesterday and she looks anxious..I just want to know how much of the exam was repeated questions..how much are new questions..thanks
    if you are good enough, you actually don't have to guess any of them. it is an easy paper with f325 standards. (even though i made a lot of mistakes......)
    it's normal to feel anxious after the exam if you need a very good grade, one careless mistake could cause everything.
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    (Original post by yiz)
    Did anyone use redox systems 6 and 7 in that 6 marker?
    I can't remember the numbers but were 6 and 7 the dichromate one and the complicated Fe one? I used those, I'm pretty sure u had to to show Cr 3+ acting as a reducing agent


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    (Original post by 1lilypad1)
    I can't remember the numbers but were 6 and 7 the dichromate one and the complicated Fe one? I used those, I'm pretty sure u had to to show Cr 3+ acting as a reducing agent


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    I did that too. I was just wondering cos I saw that someone used 5 and 6 and I got a bit worried haha
 
 
 
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