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    Not sure how to work this out even though it's only worth one mark.
    Bromine has two isotopes BR-79 and Br-81 the relative atomic mass of br is 79.9 calculate the percentage of br-79 atoms in a sample of bromine.


    Hopefully you can follow those workings through!
    Essentially, it's just letting the abundances = x and y, using your knowledge about how to calculate it the regular way, but instead using some algebra and basic simultaneous equations
    It looks like a new spec question to me - they like to ask questions like this in the NEW AS chemistry, and just for one mark, so harsh I know!
    Either way, any questions, ask me Hopefully that's the right answer It's either that or 45% if I've gotten mixed up.

    Good luck in your exam, presumably on Friday next week!
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