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Law of Multiple Proportions practice work

  1. Sep 11, 2015 #1
    1. The problem statement, all variables and given/known data









    5 There are four common oxides that contain only N and O. The composition of three of the

    compounds is shown below. According to the law of Multiple proportions, which of the

    four (a, b, c, d) could not be one of the four oxides of nitrogen?


    a. 1.000 g(N) combined with 2.8571 g(O)



    b. 1.000 g(N) combined with 1.1429 g(O)



    c. 1.000 g(N) combined with 1.7143 g(O)



    d. 1.000 g(N) combined with 1.5000 g(O)

    2. Relevant equations
    x=(amount of whole substance-amount given)/amount given

    3. The attempt at a solution
    I'm struggling badly here, any tips would be much appreciated. I don't understand how I can get the answer without knowing the grams of the whole substance (N and O together).
     
  2. jcsd
  3. Sep 11, 2015 #2

    Bystander

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    It's given to you in the statement.
     
  4. Sep 12, 2015 #3

    Borek

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    What is the mass of the product if you combine 1.0 g of something with 1.5 g of something else (and you are guaranteed they reacted completely)?
     
  5. Sep 12, 2015 #4

    epenguin

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    Not that you need to know it - nor will it help you. The question tells you what law to use.
     
  6. Sep 13, 2015 #5
    Couldn't you convert those grams to moles, divide the moles of oxygen by the moles of nitrogen, and see which ratio isn't possible in a molecule for the given elements?
     
  7. Sep 13, 2015 #6

    epenguin

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    Nothing of that, the necessary information isn't given and the question loses point if it is. This question is prior to the mole concept, and you could say is an important part of its justification.
     
  8. Sep 13, 2015 #7
    I'm curious to see how this problem will be solved then, because I can't make anything from the numbers given. For the record, though:

    amount of whole substance = amount given + amount of other substance
    x = (amount of whole substance - amount given)/amount given
    x = (amount given + amount of other substance - amount given)/amount given
    x = amount of other substance/amount given

    Because the bolded cancel each other out. Tell me if I'm giving too much of the answer away, mods.
     
  9. Sep 13, 2015 #8

    epenguin

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    Well I see people are stuck so it is a good excercise. (A good academic excercise - academic because it is with made-up figures, like a lot we got recently probably from same source, but at least ideally these make sense which others didn't even.) People are stuck because it is too elementary for them, comes from lesson 1 or at most 2 in quantitative chemistry. And possibly lessons 1 and 2 were dropped from many curriculae.
    You only have to know what the quoted law actually is and I don't know what's stopping the OP or anyone else but Hushh!
     
    Last edited: Sep 13, 2015
  10. Sep 13, 2015 #9

    Bystander

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    When "stumped" or in doubt, READ the question.
    2. Relevant equations
    x=(amount of whole substance-amount given)/amount give
     
  11. Sep 13, 2015 #10

    Borek

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    First of all - what does the law of multiple proportions say? Quote it.
     
  12. Sep 13, 2015 #11

    epenguin

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    The zloty has dropped! :oldbiggrin:
     
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