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Homework Help: How to verify your claim in this fire experiement?

  1. Aug 21, 2011 #1
    1. The problem statement, all variables and given/known data

    If we initially lighted a candle, and then put a jar over it, what can we say about the fire? What kind of observations can we make?

    How can you verify your claim?

    3. The attempt at a solution

    Well the observations are quite obvious. The flame is put off soon or later.

    I want to know is it true that there is as much CO2 produced as O2 used? If the initial state has 10 C, and 10 O2 molecules, we can make 10 CO2. The mass + energy is conserved, also.
    What kind of scientific sensor / tool can detect and find out the composition of air (quantitatively) ?

    I haven't done chemistry for a few years so I am sorry for the abrupt question here. Thanks!
  2. jcsd
  3. Aug 22, 2011 #2


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    Staff: Mentor

    If there is 10 plus 10 you are OK, but what if you have 5 plus 10, or 10 plus 5?
  4. Aug 22, 2011 #3
    Hi Borek,

    Thanks for the response.

    With 10 carbon and 5 O2, you can only make 5 CO2 and 5 carbon atoms left alone.
    With 5 carbon atoms and 10 O2, you can make 5 CO2 as well.

    So" the number of O2 molecules used should equal to the number of carbon atoms used; the total energy and mass of the system should be conserved inside."

    This brings up two more sub questions:
    1. how can we make sure there is no loss of heat? or how do we calculate the loss of heat because the jar is not insulated-proof?
    2. what are other chemical products produced during the burning process?

    Precisely, we do need to measure the inside quantitatively in order to verify our claims that heat is generated and oxygen is consumed during burning and that carbon dioxide are also produced.

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