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  1. #1
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    chemistry question

    An element containing only 2 isotopes , 50P and 53P (50 and 53 are the nucleon numbers) have been analysed in a mass spectrometer . If the relative atomic mass of P is 51.9 , what is the relative abundance of 50P ?

    THanks ..
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  2. #2
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    e^(i*pi)'s Avatar
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    Quote Originally Posted by thereddevils View Post
    An element containing only 2 isotopes , 50P and 53P (50 and 53 are the nucleon numbers) have been analysed in a mass spectrometer . If the relative atomic mass of P is 51.9 , what is the relative abundance of 50P ?

    THanks ..
    If an element X has isotopes of X_a \: , \: X_{b} \: , \: X_c \: ... \: X_n and relative abundance n_a \: , \: n_{b} \: , \: n_c \: ... \: n_n respectively (note that the sum of relative abundances is always 1) then the relative atomic mass ( M_r) is given by:

    M_r = {X_an_a + X_bn_b + X_cn_c + ... + X_nn_n}

    --------

    As a rough check you can check the location of 50, 51.9 and 53 on a number line from 50 to 53. Note that 51.9 lies about 2/3 of the way along it thus it would follow that it will be roughly 1/3 of 50 and 2/3 of 53.

    In your case

    • M_r = 51.9
    • X_a = 50
    • n_a = n_a
    • X_b = 53
    • n_b = (1-n_a)


    51.9 = 50n_a + 53 - 53n_a

    Solve for n_a. Express in whichever method your teacher wants.
    Last edited by e^(i*pi); June 9th 2009 at 09:58 AM. Reason: putting in a small check for answer
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  3. #3
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by thereddevils View Post
    An element containing only 2 isotopes , 50P and 53P (50 and 53 are the nucleon numbers) have been analysed in a mass spectrometer . If the relative atomic mass of P is 51.9 , what is the relative abundance of 50P ?

    THanks ..
    you are missing information. i believe when you typed "P", you meant to type either "50P" or "53P". please make the necessary changes and make sure there are no other errors
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  4. #4
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    Quote Originally Posted by Jhevon View Post
    you are missing information. i believe when you typed "P", you meant to type either "50P" or "53P". please make the necessary changes and make sure there are no other errors
    that 50 should be higher(its the nucleon number) . I cant find a way to post it here .
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  5. #5
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    Quote Originally Posted by thereddevils View Post
    An element containing only 2 isotopes , 50P and 53P (50 and 53 are the nucleon numbers) have been analysed in a mass spectrometer . If the relative atomic mass of P is 51.9 , what is the relative abundance of 50P ?

    THanks ..
    Chemistry questions can be posted here: http://www.chemistryhelpforum.com/chemistry-help/
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