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    Doing a bit of chemistry revision and ive come across a section that i havnt been able to understand, and was hoping for some feedback

    When it gives you an acid, how do you know wether its a strong or weak acids? I know the definition of a weak acid is it dissociates its Hydrogen ions incompletely, but i still dont understand how you tell from just the formula.

    Hcl for example.. how do i know wether its weak or strong?

    Thanks
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    hmm, I think for most of the syllabus' (syllabi?) you are just to know the main acids and whether they are strong or not.

    HCl (hydrochloric), H2SO4 (sulfuric) and HNO3 (nitric) acids are the main strong ones.
    and organic acids such as ethanoic or propanoic are weak.

    my teacher/textbook has taught me nothing more than that they fully ionise in water and dissociate completely to H+ ions etc
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    I think you just have to know, or use the acid dissociation constant
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    (Original post by Mally-xo)
    hmm, I think for most of the syllabus' (syllabi?) you are just to know the main acids and whether they are strong or not.

    HCl (hydrochloric), H2SO4 (sulfuric) and HNO3 (nitric) acids are the main strong ones.
    and organic acids such as ethanoic or propanoic are weak.

    my teacher/textbook has taught me nothing more than that they fully ionise in water and dissociate completely to H+ ions etc
    Thanks so much for the quick reply
    I'll just learn it like that then Thankyou
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    (Original post by LukeNunn)
    Thanks so much for the quick reply
    I'll just learn it like that then Thankyou
    that is alright let me know if you need any more help, I am revising acids at the moment for my exam in january.
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    For HCl I think you are just supposed to know that it is a strong acid..
    You'll know if somethings a weak acid since they'll ask you for the Ka of the acid I would think.

    Just make sure you can do everything it says on this specification: http://store.aqa.org.uk/qual/gce/pdf/AQA-2420-W-SP.PDF

    Assumed you're doing chem4 with AQA
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    HBr and HI are also strong I think, and phenol is weak. This is all I know
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    (Original post by LukeNunn)
    Doing a bit of chemistry revision and ive come across a section that i havnt been able to understand, and was hoping for some feedback

    When it gives you an acid, how do you know wether its a strong or weak acids? I know the definition of a weak acid is it dissociates its Hydrogen ions incompletely, but i still dont understand how you tell from just the formula.

    Hcl for example.. how do i know wether its weak or strong?

    Thanks
    When the anion produced (also called the conjugate base) is a something stable, like a halide, sulphate or nitrate, you get a strong acid. Where the anion is less stable, like carboxylate from carboxylic acid groups or alkoxide from alcohol groups, it is a weak acid.
 
 
 
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