Self test 8.12A

[Mariane Sanchez 1E]

The question says: " The thermochemical equation for the combustion of cyclohexane, C6H12, is C6H12(l) + 9 O2(g) -> 6 CO2(g) + 6 H2O(l), deltaH = - 3920 kJ at 298 K. What is the change in internal energy for the combustion of 1.00 mol C6H12(l) at 298 K?"

I used the formula
deltaU= deltaH-delta(n)RT but got a different answer from the book. I got -3282.56KJ but the book says -3.91x10^3. Am I using the right formula or did I just do an algebra mistake?

stuff I plugged in--
deltaH=-3920kj
delta(n)=-3mol
T=298K
R=8.314

[Andy Nguyen 1A]

I used those same numbers and got the answer from the book. I plugged in
-3920 kJ = deltaU + (-3 mol) * (.008314 kJ/Kmol) * 298K. Then I solved for deltaU.