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What fraction of the air molecules

  1. Dec 1, 2011 #1
    1. The problem statement, all variables and given/known data
    What fraction of the air molecules in a house must be pushed outside while the furnace raises the inside temperature from 17.0° C to 28.0° C? The pressure does not change since the house is not 100% airtight.

    2. Relevant equations
    v2/v1=17+273/28+273
    =.963


    Why is my answer wrong
     
  2. jcsd
  3. Dec 1, 2011 #2

    gneill

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    Staff: Mentor

    You've calculated the fraction that's left inside rather than the fraction that was pushed outside.
     
  4. Dec 1, 2011 #3
    is it .037?
     
  5. Dec 1, 2011 #4

    gneill

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    Staff: Mentor

    Is that a guess or do you have a reason to back up that number?
     
  6. Dec 2, 2011 #5
    its supposed to says 3.7 percent... I subtracted the 96.3 from 100
     
  7. Dec 2, 2011 #6

    gneill

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    Staff: Mentor

    Then that's okay. Looks good.
     
  8. Dec 2, 2011 #7
    I put the answer but for some reason its still saying its incorrect?
     
  9. Dec 2, 2011 #8

    gneill

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    Staff: Mentor

    Is there a particular answer format that the question requires? Is it finicky about significant digits?
     
  10. Dec 2, 2011 #9
    No and No... Im not sure why its doing this.
     
  11. Dec 2, 2011 #10

    gneill

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    Staff: Mentor

    :confused: I don't know what else to suggest. I can't think of any other reasonable interpretation of 'fraction of the air molecules' that would lead to a different result.
     
  12. Dec 2, 2011 #11
    yeh, Thank you for your help, Im going to email my proffessor about the question
     
  13. Dec 2, 2011 #12

    gneill

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    Staff: Mentor

    Another Homework Helper* has suggested that it is perhaps possible that the question is looking for (n28C-n17C)/n28C ("what fraction of the gas was pushed out") instead of (n28C-n17C)/n17C ("what fraction of the gas will be pushed out"). It would make a small but noticeable difference in the result.


    * Thanks D H!
     
  14. Dec 2, 2011 #13
    Yes!!! that was correct Thank you D H!!!
     
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