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Thread: Calculating Isotope Abundance

  1. #1 Calculating Isotope Abundance 
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    I've come up against another difficulty in my endeavor for learning basic chemistry.
    As an example, I'll give this equation:

    Element___Isotope___Mass Of Isotope_____Proportion___Mass X Proportion___Sum

    ___________52/24________52.000_____X_____A_____=___52.000 X A
    Cr________________________________________________ __________+= 51.996
    ___________51/24________51.000_____X_____B_____=___51.000 X B



    If you could just envision the problem in the absence of the lines. I tried to make the problem as least confusing as possible and I apologize for the amateur construction of my diagram. I've done a number of problems similar to this and I still can't seem to grasp the concept of what's really going on here. I'd really appreciate some feedback on this as to this.
    Thanks.


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  3. #2  
    Geo
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    Is it based on the isotope abundance in nature?

    There's 250 times as much A, as there is B? - present in nature?


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  4. #3  
    Reptile Dysfunction drowsy turtle's Avatar
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    (The proportions of each isotope added together must equal 1, otherwise the whole mass of the element is not accounted for)


    (previous step multiplied by 51 on both sides of the '=' sign)




    (51B=51-51A, derived from the step above)


    (subtracted the 51A out the brackets, from the original 52A


    (subtracted 51 from both sides)



    (derived from A+B=1)





    Quote Originally Posted by Geo
    There's 250 times as much A, as there is B? - present in nature?
    249 times as much actually. of the element is present as isotope B.



    Edit: assuming there are no other naturally occurring isotopes, which I realised is not explicitally mentioned in the OP.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
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  5. #4  
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    I'm not sure I understand.

    52.000A + 51.000 = 51.996
    52.000A + (51.000 - 51.000A) = 51.996

    How do you know what to do after this step?
    Do you cross out some parts of the equation that leave you with the number you're suppose to use to add to A and find the sum?
    In other words, how do you know to add A to 52.000 instead of 51.000 and vise versa.
    And on some problems, you have to add 2.000A to whichever number.
    How do you know when to add 2.000 A instead of 1.000 A?
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  6. #5  
    Reptile Dysfunction drowsy turtle's Avatar
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    I'll edit my previous post to explain the steps.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
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