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    (Original post by samb1234)
    Yeah 37/40 is an A. Its pretty worrying that 1 mark on the practical can cost you 1% of your as course

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    That's ridiculous.
    I'll have to smash unit 1 and 2...
    My average is 118UMS over 7 unit 1 I've done so I should be okay but unit 2 idk lol I got some time but still


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    (Original post by C0balt)
    That's ridiculous.
    I'll have to smash unit 1 and 2...
    My average is 118UMS over 7 unit 1 I've done so I should be okay but unit 2 idk lol


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    Yeah unit 1 is normally very basic but unit 2 can be a bit more unpredictable

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    (Original post by C0balt)
    Which is what I said XD


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    Yeah lol xD
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    The jump from unit 1 to unit 2 is 10x bigger than the jump from gcse to unit 1...
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    Hi everyone.
    OCR Chemistry AS level
    lovin' the thread
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    (Original post by BBeyond)
    The jump from unit 1 to unit 2 is 10x bigger than the jump from gcse to unit 1...


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    Agreed,I'm so nervous for the exams.
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    (Original post by BBeyond)
    The jump from unit 1 to unit 2 is 10x bigger than the jump from gcse to unit 1...
    I don't understand how they have the same weighting and time is the same for edexcel. I'd have preferred if it was like physics, where they split units by topics.


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    (Original post by C0balt)
    I don't understand how they have the same weighting and time is the same for edexcel. I'd have preferred if it was like physics, where they split units by topics.


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    At least unit 2 is after half term

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    (Original post by Kadak)
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    Agreed,I'm so nervous for the exams.
    Ikr so close now

    (Original post by C0balt)
    I don't understand how they have the same weighting and time is the same for edexcel. I'd have preferred if it was like physics, where they split units by topics.


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    I find it beyond stupid that I can go from 77-80 on unit 1 papers to struggling to reach 60 on unit 2 papers when I've put far more time into unit 2...
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    (Original post by samb1234)
    At least unit 2 is after half term

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    My school doesn't have half term this term.


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    (Original post by BBeyond)
    Ikr so close now



    I find it beyond stupid that I can go from 77-80 on unit 1 papers to struggling to reach 60 on unit 2 papers when I've put far more time into unit 2...
    And funnily enough the grade boundaries aren't that much lower


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    (Original post by C0balt)
    And funnily enough the grade boundaries aren't that much lower


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    If lower at all, quite a lot of papers seem to have higher boundaries, it truly puzzles me tbh.
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    We did another unit 1 and unit 2 mock for chem, i think it was unit 1 2013 may paper and last years unit 2 paper. The unit 1 seemed far harder than the unit 2 one, the unit 2 one was pretty easy.
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    hey guys can you help me out with something,
    let's say in a practical you were given a few unknown substances and you had to do these tests on them:
    1. add barium chloride, record result then add dilute nitric acid + record result
    2. add silver nitrate, record result then add dilute nitric acid + record result
    and the results were white, cream, yellow precipitates that either dissolves after the dilute nitric acid or didnt, and one substance which showed fizzing...what would any of this mean. hypothetically.
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    (Original post by wil97)
    hey guys can you help me out with something,
    let's say in a practical you were given a few unknown substances and you had to do these tests on them:
    1. add barium chloride, record result then add dilute nitric acid + record result
    2. add silver nitrate, record result then add dilute nitric acid + record result
    and the results were white, cream, yellow precipitates that either dissolves after the dilute nitric acid or didnt, and one substance which showed fizzing...what would any of this mean. hypothetically.
    Barium chloride tests the presence of sulphate ion. Positive result gives a white precipitate of barium sulphate. Don't you add nitric acid before addition of barium chloride to eliminate he possibility of carbonate or hydrogen carbonate ions. If carbonate or hydrogen carbonate ions are present there will be fizzing, which is carbon dioxide.

    Silver nitrate is the test for halide ions. With the presence of chloride ion white precipitate forms, with bromide cream precipitate, and with iodide yellow precipitate. White precipitate dissolves in both dilute and concentrated ammonia, cream precipitate only dissolves in concentrated ammonia and yellow precipitate does not dissolve in ammonia. Nitric acid is added BEFORE the addition of silver nitrate to eliminate the possibility of other ions as said above.


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    (Original post by wil97)
    hey guys can you help me out with something,
    let's say in a practical you were given a few unknown substances and you had to do these tests on them:
    1. add barium chloride, record result then add dilute nitric acid + record result
    2. add silver nitrate, record result then add dilute nitric acid + record result
    and the results were white, cream, yellow precipitates that either dissolves after the dilute nitric acid or didnt, and one substance which showed fizzing...what would any of this mean. hypothetically.


    If you add barium chloride and get a white precipitate, your original sample contained sulphate (SO4^2- ions).

    When you add dilute nitric acid then silver nitrate and you get:

    White precipitate = chloride ions (Cl-)

    Cream precipitate = bromide ions (Br-)

    Yellow precipitate = iodide ions (I-)

    If you aren't confident with the colours, you can do another test with the silver halides, as they have different solubilities in aqueous ammonia.

    AgCl dissolves in dilute and concentrated ammonia

    AgBr is partially soluble/doesn't dissolve in dilute aqueous ammonia but does dissolve in conc aqueous ammonia.

    AgI doesn't dissolve in either

    Hope this helps!
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    Doing a physics past paper and my inner chemist was stimulated.

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    (Original post by C0balt)
    Doing a physics past paper and my inner chemist was stimulated.

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    Haha 😄.When we did semi conductors my inner chemistry was stimulated.
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    (Original post by Kadak)
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    Haha 😄.When we did semi conductors my inner chemistry was stimulated.
    Oh yeah :lol: same with excitation - I was like "flame tests :mmm:"


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    Hello again, so I came across a question that im confused on
    I calculated the molar mass of a compound to be 200 and then it asks you to
    Suggest the formula of the acid HX given that it only contains C, H and O
    Please show your working out.
    Thank you

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