Hi, my AP Chemistry class is learning how to calculate the heat of formation and bond energies. I'm stuck on part 2 of this problem:
Consider the combustion of ethane:
C2H6(g) + 7/2O2(g) -> 2CO2(g)+3H2O(l) change in heat at standard conditions = -1559 KJ/mol
I used Hess' law to find the heat of formation of ethane, and got -85.51 KJ/mol (which according to my teacher, is the answer).
The next part confuses me: For the above reaction, how much energy is released if 1Kg of water is formed? (ans: -28870.5KJ)
Should I convert 1Kg to moles of water? 1Kg*(1000g/1Kg)(1mol/18g) = 55.56mol. Then recalculate heat of formation using Hess's Law? The numbers get so strange, I don't think I'm using the right method.
Thank you!