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Molar Mass Problem

  1. Jan 22, 2014 #1
    1. The problem statement, all variables and given/known data

    2 A + 3 B + 1000 kJ ==> 4 C

    where A,B,C are molecules. A mass of 35.5 g of A is used with the right quantity of B, and the mixture of reactants is heated with an energy of 750 kJ. Find the molar mass of A.

    2. The attempt at a solution

    Heat released per mole in terms of "A" : 1000 kJ / 2 = 500 kJ/mole "A"

    Finding number of moles used:

    (750 kJ) / (500 kJ/mole) = 1.5 mol "A"

    Molar mass = (35.5 grams) / (1.5 mol) = 23.7 g/mol
     
  2. jcsd
  3. Jan 31, 2014 #2

    Borek

    User Avatar

    Staff: Mentor

    Your approach looks OK, but the question is poorly worded - it doesn't say anything about whether there was enough heat to react all of A.
     
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