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anonymous

  • one year ago

Naturally occurring copper exists in two isotopic forms. 63Cu and 65Cu. The atomic mass of copper is 63.55 amu. What is the approximate natural abundance of 63Cu?

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  1. aaronq
    • one year ago
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    It's a weighted average. Atomic mass = (abundance of 63Cu* mass of 63Cu)+ (abundance of 65Cu* mass of 65Cu)

  2. anonymous
    • one year ago
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    But how do you find the abundance? All I was given was in the question.

  3. anonymous
    • one year ago
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    Use algebra. \[63x+65y=63.55\] \[x+y=1\] It would be 1 and not 100 because natural abundance is in percentage. 80% would be 0.80 and 70% would be 0.70 Natural abundance of both isotopes would need to be at 100% since those are the only isotopes for copper. 100%=1

  4. anonymous
    • one year ago
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    There is another method but I forgot.

  5. anonymous
    • one year ago
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    Alright. Thanks.

  6. anonymous
    • one year ago
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    No problem! But what did you get for each?

  7. anonymous
    • one year ago
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    I got 63 Cu = 62.925989 and 65 Cu = 64.9277929

  8. anonymous
    • one year ago
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    Then I did all the math and got x=.689

  9. anonymous
    • one year ago
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    Sorry about the late replies.

  10. anonymous
    • one year ago
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    63Cu = 68.95% 65 Cu = 31.05%

  11. anonymous
    • one year ago
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    You did the math wrong. 63(0.6895)+65(0.3105) did not equal 63.55. It equaled 63.62 so your answer is a bit close to the real one. You can check your answers this way.

  12. anonymous
    • one year ago
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    I'll have to go back and see what I did wrong. I guess my professor is wrong too. lol I got the same answer as them. Probably should let them know.

  13. anonymous
    • one year ago
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    They are wrong because my answers matches to 63.55 amu.

  14. anonymous
    • one year ago
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    I'll let them know. Thanks for checking the math for me.

  15. anonymous
    • one year ago
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    I'm bad about making little mistakes in the math. It can really throw it off.

  16. anonymous
    • one year ago
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    No problem!

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spraguer (Moderator)
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