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    (Original post by TeaAndTextbooks)
    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

    Posted from TSR Mobile
    Have you got the full question to post up? There must be additional information given in earlier parts of the question that will help in getting the answer for this part.

    When they say HX I assume it must be a hydrogen halide but that clearly isn't the case if it only contains Carbon, Hydrogen and Oxygen.

    It possible could be an alcohol with an OH group (or even multiple OH groups!); a carboxylic acid.
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    (Original post by TeaAndTextbooks)
    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

    Posted from TSR Mobile
    Name:  ImageUploadedByStudent Room1429478496.579058.jpg
Views: 77
Size:  159.4 KB
    See the attached.
    Assumed the acid to be carboxylic acid (it could've been carbonic acid but it doesn't add up to 200). It is weird that it is shown to be HX though.


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    (Original post by C0balt)
    Oh yeah :lol: same with excitation - I was like "flame tests :mmm:"


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    Haha for me it was the other way round. In one chemistry paper it asked why different elements burned with different colours so I obviously had to include the formula giving the wavelength of the emitted photon

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    (Original post by C0balt)
    Assumed the acid to be carboxylic acid (it could've been carbonic acid but it doesn't add up to 200). It is weird that it is shown to be HX though.

    (Original post by James A)
    When they say HX I assume it must be a hydrogen halide but that clearly isn't the case if it only contains Carbon, Hydrogen and Oxygen.
    Things like HA and HX are often used in secondary school chemistry to represent hypothetical carboxylic acids that dissociate into H+ and A- respectively.
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    (Original post by samb1234)
    Haha for me it was the other way round. In one chemistry paper it asked why different elements burned with different colours so I obviously had to include the formula giving the wavelength of the emitted photon

    Posted from TSR Mobile
    Hahaha
    That flame test thought was in lesson though. We learnt excitation later than flame tests that's why

    I haven't come across with the flame test question yet, so I'll see if I get the urge.
    But I'm pretty sure I will now say photons instead of electromagnetic wave which I used to say at the beginning of the year.


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    (Original post by Hype en Ecosse)
    Things like HA and HX are often used in secondary school chemistry to represent hypothetical carboxylic acids that dissociate into H+ and A- respectively.
    Never come across that lol only HX I have seen was halides in my AS course
    Now I won't randomly assume in my exams, great


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    (Original post by C0balt)
    Hahaha
    That flame test thought was in lesson though. We learnt excitation later than flame tests that's why

    I haven't come across with the flame test question yet, so I'll see if I get the urge.
    But I'm pretty sure I will now say photons instead of electromagnetic wave which I used to say at the beginning of the year.


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    I do the same thing with coulombs law for any ionisation energy question

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    (Original post by samb1234)
    I do the same thing with coulombs law for any ionisation energy question

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    What board are you with for physics?

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    Thanks alot that was helpful I think I understand it now. It was just a class question so my teacher probably worded it wrong but I'm sure your answer is correct.
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    (Original post by C0balt)
    What board are you with for physics?

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    Aqa

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    (Original post by samb1234)
    I do the same thing with coulombs law for any ionisation energy question

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    Btw we don't do coulombs law I just happen to know it

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    (Original post by TeaAndTextbooks)
    Thanks alot I get it now
    Glad to be of help

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    (Original post by samb1234)
    Btw we don't do coulombs law I just happen to know it

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    Yeah I was like "were we examined in the law???"

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    (Original post by C0balt)
    Yeah I was like "were we examined in the law???"

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    You learn a lot of random stuff when one of your best friends read the entire Feynman lectures

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    (Original post by C0balt)
    Never come across that lol only HX I have seen was halides in my AS course
    Now I won't randomly assume in my exams, great


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    Yeah it's really common in Scotland, but the giveaway in that question was " ... the acid HX".
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    (Original post by Hype en Ecosse)
    Yeah it's really common in Scotland, but the giveaway in that question was " ... the acid HX".
    Yea said acid so just assumed carboxylic :yy:

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    (Original post by samb1234)
    You learn a lot of random stuff when one of your best friends read the entire Feynman lectures

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    I'd read about the law before but didn't quite get the equation so I kinda got scared when you mentioned it lol

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    (Original post by C0balt)
    I'd read about the law before but didn't quite get the equation so I kinda got scared when you mentioned it lol

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    The only bit that is useful really is the fact that it means that the attraction is inversely proportional to r^2

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    (Original post by samb1234)
    The only bit that is useful really is the fact that it means that the attraction is inversely proportional to r^2

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    As far as chemistry goes anyway

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    (Original post by samb1234)
    As far as chemistry goes anyway

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    Ah so further apart the electron the less attraction there is so less ionisation energy and all that argument

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