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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 rory58824)
    Just remember guys, questions like that disulfide bond are the most challenging ones. That one was only 2 marks out of 100. If you get a similar situation in the real one just move on and try to score best on the other 98 marks. You're better off getting 5 easy marks on a buffer solution than spending a long time on a 2 mark question.
    Yeah that's true, but I'd still like to understand it
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    (Original post by AqsaMx)
    Yeah that's true, but I'd still like to understand it
    Check this video out, I don't have the time to explain it at the moment but I think this is a pretty good explanation. Go to 33:32 in the video if you want the explanation for that question:

    https://www.youtube.com/watch?v=pwrLHwFh4KM
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    Can someone please help me out with this?
    I dont understand enthalpy change of solution and enthalpy change of hydration

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    To those who helped me in the Kc questions, thank you guy! Now for the 2nd question:

    In the UK, almost all the sulphuric acid manufactured uses sulphur as a startingmaterial for SO2 production. In some countries, metal ores such as zinc sulphide,ZnS, are used instead to form SO2 by heating with air.(i) Construct a balanced equation to show the reaction that takes place whenzinc sulphide is heated in air.

    Obviously I thought:

    ZnS + O2 ---> SO2 + Zn

    However the mark scheme only rewards one mark for this but rewards the two full marks for this:

    2ZnS + 3O2 → 2ZnO + 2SO2

    Anyone know how and why??
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    Is anyone able to give me tips/advice on the evaluative for the relative strengths of weak acids?
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    (Original post by Hunnybeebee)
    To those who helped me in the Kc questions, thank you guy! Now for the 2nd question:

    In the UK, almost all the sulphuric acid manufactured uses sulphur as a startingmaterial for SO2 production. In some countries, metal ores such as zinc sulphide,ZnS, are used instead to form SO2 by heating with air.(i) Construct a balanced equation to show the reaction that takes place whenzinc sulphide is heated in air.

    Obviously I thought:

    ZnS + O2 ---> SO2 + Zn

    However the mark scheme only rewards one mark for this but rewards the two full marks for this:

    2ZnS + 3O2 → 2ZnO + 2SO2

    Anyone know how and why??
    Im not sure but isnt sulfuric acid h2SO4 so you would need 2 SO2? im probs wrong

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    (Original post by AqsaMx)
    Is anyone able to give me tips/advice on the evaluative for the relative strengths of weak acids?
    Anyone please?
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    Guys I'm soo scared for chemistry; what's everyone doing at this point? Notes or have you guys started doing past papers; I'm retaking both f321 and f322 aswell Sitting A2 this summer👀😭


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    (Original post by AqsaMx)
    Anyone please?
    I don't remember doing it but calculating ph would defo come up make sure you know all the mathy part of it? Maybe go over indicators aswell?


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    (Original post by AqsaMx)
    Anyone please?
    Know about acids, bases, indicators inside out - know ranges of indicators, remember how to work out strong acid, strong base, weak acid. Practise your moles questions, etc, and underline words in question, won't be too difficult, youll know EVERYTHING on the test so dont worry
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    (Original post by totabatouta)
    I don't remember doing it but calculating ph would defo come up make sure you know all the mathy part of it? Maybe go over indicators aswell?


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    You know with regards to indicators do you actually need to know colour changes and stuff?
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    (Original post by zirak46)
    Know about acids, bases, indicators inside out - know ranges of indicators, remember how to work out strong acid, strong base, weak acid. Practise your moles questions, etc, and underline words in question, won't be too difficult, youll know EVERYTHING on the test so dont worry
    Thank you so much, I appreciate it
    But you know cos the paper is relative strength of weak acids, could they still ask about bases and strong acids?
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    Does anyone have the f325 2015 past paper & mark scheme? I really need it for revision!
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    Your teachers should have it, ask your head of department. Otherwise, its not important till youve done all the other past papers tbh

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    (Original post by AqsaMx)
    You know with regards to indicators do you actually need to know colour changes and stuff?
    No, you'll be given any sort of colour changes in the exam. All you need to do is identify the most suitable indicator to use (they might give you 3 to choose from).
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    Can anyone explain why it's difficult to determine the lattice enthalpy of sodium carbonate using a Bourne harbour cycle? The MS says because you need to CO32- ions but I don't get what this means? :/
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    (Original post by AqsaMx)
    Can anyone explain why it's difficult to determine the lattice enthalpy of sodium carbonate using a Bourne harbour cycle? The MS says because you need to CO32- ions but I don't get what this means? :/
    Carbonate ion is composed of two elements


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    (Original post by zirak46)
    Your teachers should have it, ask your head of department. Otherwise, its not important till youve done all the other past papers tbh

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    What about if your teachers refuse to give it to you yet and you have completed all past papers?
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    Can anyone with the ocr endorsed book help me on page 89 and explain the carbon environments in the last 3 benznes pls bc I thought they'd only be 4 I the second one as it's symmetrical?

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    Actually dw I worked it out lol

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