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Math Help - Chemistry Moles Question

  1. #1
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    Chemistry Moles Question

    I just had this question on a quiz and I'm not sure what I did wrong.
    Question: Calculate the number of hydrogen atoms in 0.125 g of citric acid H3C6H5O7

    Heres what I did..
    I found the percent composition of hydrogen to be 4.17%, then I found the total moles of hydrogen in citric acid and multiplied it by 0.0417 (this is where I think i went wrong), then multiplied that number by avagadros number to get 1.63 X 10^19 particles.

    Anyone care to correct me and provide right answer?

    Thanks.
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  2. #2
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    Quote Originally Posted by Shout View Post
    Question: Calculate the number of hydrogen atoms in 0.125 g of citric acid C_6H_8O_7
    How did you get 1.63 X 10^19 particles? You have all the working out correct... but not the answer.

    First part is correct, 0.125g * 0.0417 = 0.0052125 moles of hydrogen

    The next part, you have the method correct, but not the answer.

    The Avogadro constant is 6.022(10^23)

    0.0052125 moles * [6.022(10^23)] = ...

    I'm sure you can type that into the calculator yourself?

    And you shouldn't get 1.63 X 10^19.
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