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    So how would we know the colours of a solution or a precipitate? Is there like a general rule?

    eg. Silver chloride
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    (Original post by Me14)
    So how would we know the colours of a solution or a precipitate? Is there like a general rule?

    eg. Silver chloride
    Unless you have a computer and some pretty advanced software there is no way to know. You have to learn them.
    There are trends in groups of similar compounds and these trends can be rationalised but that is way, way above A-level
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    (Original post by Me14)
    So how would we know the colours of a solution or a precipitate? Is there like a general rule?

    eg. Silver chloride
    Memorise the ones you need to know for A2 - that's all I can suggest, really
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    (Original post by thegodofgod)
    Memorise the ones you need to know for A2 - that's all I can suggest, really
    I think it's a little bit better than that.

    For example, you can predict the colour of any Cu2+ salt or complex (I say "predict", of course) - you don't need to memorize the different colours for copper sulphate, copper nitrate, copper hydroxide, etc. (I realize I've actually picked a bad example with Cu2+ because there are exceptions you might need to know at A2.)
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    (Original post by Big-Daddy)
    I think it's a little bit better than that.

    For example, you can predict the colour of any Cu2+ salt or complex (I say "predict", of course) - you don't need to memorize the different colours for copper sulphate, copper nitrate, copper hydroxide, etc. (I realize I've actually picked a bad example with Cu2+ because there are exceptions you might need to know at A2.)
    Well I suppose that's true when it comes to some transition metal ions such as Cr3+, where all (I think) salts and ions are green, but the point I'm making is that there are pretty much always exceptions to rules, which just have to be learned; they cannot always be guessed intuitively
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    (Original post by thegodofgod)
    Well I suppose that's true when it comes to some transition metal ions such as Cr3+, where all (I think) salts and ions are green, but the point I'm making is that there are pretty much always exceptions to rules, which just have to be learned; they cannot always be guessed intuitively
    It would probably help if there was a list, comprehensive for UK A-level at least, of all the main solutions and their colours. I can remember a day I spent with JMaydom and charco just blasting through ion after ion and what colour they are likely to be when you've got a precipitate containing them and a solution. So it's not that simple an issue
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    (Original post by Big-Daddy)
    It would probably help if there was a list, comprehensive for UK A-level at least, of all the main solutions and their colours. I can remember a day I spent with JMaydom and charco just blasting through ion after ion and what colour they are likely to be when you've got a precipitate containing them and a solution. So it's not that simple an issue
    Which is exactly what I said in my original post

    (Original post by thegodofgod)
    Memorise the ones you need to know for A2 - that's all I can suggest, really
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    (Original post by thegodofgod)
    Which is exactly what I said in my original post
    Yeah but I was lamenting the lack of any list available for you to memorize ... I wish there was (in fact, not just solution colours, but all of the observational details you need to pick up at A-level). That would save me from a lot of scrounging around near exam time.
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    (Original post by Big-Daddy)
    Yeah but I was lamenting the lack of any list available for you to memorize ... I wish there was (in fact, not just solution colours, but all of the observational details you need to pick up at A-level). That would save me from a lot of scrounging around near exam time.
    Well if you've got a decent text book / revision guide which is endorsed by the exam board, it should have a comprehensive list of all compounds and colours you need to know
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    (Original post by thegodofgod)
    Well if you've got a decent text book / revision guide which is endorsed by the exam board, it should have a comprehensive list of all compounds and colours you need to know
    I don't :mad: Finally I just made one off ChemGuide but I don't know if there's anything missing from it (i.e. either not covered from ChemGuide or which I skipped - I was short of time then and as an AS student I sometimes have to make judgement calls on what I shouldn't bother putting, out of the A2 material, on my revision notes).

    I'll busy myself making a comprehensive A-level list (maybe slightly beyond) - with help from TSR of course - after my AS exams.
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    (Original post by Big-Daddy)
    I don't :mad: Finally I just made one off ChemGuide but I don't know if there's anything missing from it (i.e. either not covered from ChemGuide or which I skipped - I was short of time then and as an AS student I sometimes have to make judgement calls on what I shouldn't bother putting, out of the A2 material, on my revision notes).

    I'll busy myself making a comprehensive A-level list (maybe slightly beyond) - with help from TSR of course - after my AS exams.
    If you do AQA and you have the Nelson Thornes A2 text book, there's a comprehensive table at the end of the transition metals topic in unit 5

    Ah, you're an AS student, so I guess you'll probably have to learn the redox silver halide reactions and AgX colours
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    (Original post by thegodofgod)
    If you do AQA and you have the Nelson Thornes A2 text book, there's a comprehensive table at the end of the transition metals topic in unit 5

    Ah, you're an AS student, so I guess you'll probably have to learn the redox silver halide reactions and AgX colours
    Yeah, standard AgF is soluble (colourless solution), AgCl is a white precipitate, AgBr is cream precipitate, AgI is yellow precipitate (that's GCSE!) What's not GCSE and yet still on our AS syllabus is that AgCl dissolves in NH3, AgBr in conc NH3 or excess of dilute NH3, and AgI does not dissolve in NH3 (in all cases this is due to the complex ion [Ag(NH3)2]+ being formed); and on exposure to sunlight, all AgX decompose, with AgCl decomposing slowest and AgI fastest (again obviously AgF doesn't decompose - it's already dissolved into the solution, you won't get a precipitate except at really high concentrations).

    That was a nice bit of AS revision But what it should tell the OP is the futility of trying to work out the colours as opposed to memorizing them.

    I don't do AQA, so I'm a bit hesitant to buy the Nelson Thornes book just for the list. Could you send/link me it in some way?
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    (Original post by Big-Daddy)
    Yeah, standard AgF is soluble (colourless solution), AgCl is a white precipitate, AgBr is cream precipitate, AgI is yellow precipitate (that's GCSE!) What's not GCSE and yet still on our AS syllabus is that AgCl dissolves in NH3, AgBr in conc NH3 or excess of dilute NH3, and AgI does not dissolve in NH3 (in all cases this is due to the complex ion [Ag(NH3)2]+ being formed); and on exposure to sunlight, all AgX decompose, with AgCl decomposing slowest and AgI fastest (again obviously AgF doesn't decompose - it's already dissolved into the solution, you won't get a precipitate except at really high concentrations).

    That was a nice bit of AS revision But what it should tell the OP is the futility of trying to work out the colours as opposed to memorizing them.

    I don't do AQA, so I'm a bit hesitant to buy the Nelson Thornes book just for the list. Could you send/link me it in some way?


    I don't have the text book any more as I gave it back in last year, but you should be able to find similar tables on line
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    (Original post by Big-Daddy)
    Yeah, standard AgF is soluble (colourless solution), AgCl is a white precipitate, AgBr is cream precipitate, AgI is yellow precipitate
    Thank you, any other ions which I can memorise the colours of?
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    (Original post by Me14)
    Thank you, any other ions which I can memorise the colours of?
    Loads. Like I said, I'd love a full list as much as you!
 
 
 
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