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Homework Help: Nuclear Reaction Problem!

  1. Oct 8, 2011 #1
    1. It has been found by experiment that the molar mass of the Rn nucleotide is 221.9703 g and that of the Po nucleotide is 217.9630 g. The molar mass of helium is 4.00150 g. Given this information, and the information from the class, calculate the energy evolved, in kJ, for the following nuclear reaction of 400.0 g of radon-222.

    2. ΔE = Δmc^2 where c is speed of light

    # of mol (n) = mass/molar mass

    3. The attempt at a solution
    Δm = 221.9703 - (217.9630 + 4.00150)
    = 5.8 x 10^-3

    ΔE = 5.8 x 10^-3 (3.0 x 10^8)
    = 1740000 J

    n = 400.0/ 221.9703
    = 1.803 mol

    How do I get the energy to be kJ/mol? My teacher said the answer should be ---- x 10^8 kJ.
  2. jcsd
  3. Oct 8, 2011 #2


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    Staff: Mentor

    Check your math - you are off by c.
  4. Oct 9, 2011 #3
    Oh yes sorry! I forgot to square c!

    But then I ended up getting:
    ΔE= 5.22 x 10^14

    What do I do now with ΔE and the number of moles of radon to figure out the energy per mole in kJ?
  5. Oct 10, 2011 #4


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    Staff: Mentor

    If two apples cost $4, what is a price in dollars per apple?
  6. Oct 10, 2011 #5


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    Science Advisor

    Also, what is a Joule? Check your units.
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