1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: 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


    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.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted