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Easy thermo chem

  1. Jun 17, 2009 #1
    The value of H° for the reaction below is -1107 kJ:
    2Ba(s) + O2(g) --> 2BaO(s)

    How many kJ of heat are released when 5.75 g of Ba(s) reacts completely with oxygen fo form BaO(s)?

    i worked out the moles of Ba which was 0.0412 then times by -1107 whcih is 46.4 however the answer is 23.2, i dont understand why becasue the is a 2 to 2 relationship between Ba and BaO? any help would be good

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  2. jcsd
  3. Jun 17, 2009 #2
    The specific enthalpy of reaction would be -1107 kJ per 2 moles of Ba consumed (or per mole of oxygen consumed or per 2 moles of BaO produced). This would give the 23.2 kJ of heat released.
  4. Jun 18, 2009 #3
    thanks, but how do u no you have to use the coeffecient of the oxygen, when the Ba is limiting?
  5. Jun 18, 2009 #4


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    Staff: Mentor

    Value is given not per mole of Ba, but per so called 'mole of reaction'.

    That's not always the case.
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