I need help solving a question about finding the change in internal energy.
The question is:
When it explodes, nitroglycerin splits into nitrogen gas, carbon dioxide, oxygen and water vapor. The enthalpy of formation is -365,0 kJ/mol for nitroglycerin, -393,5 kJ/mol for carbon dioxide and -241,8 kJ/mol for water vapor.
Calculate the enthalpy of reaction (ΔH) as well as the change in internal energy (ΔU) when nitroglycerin completely decomposes with a constant pressure of one bar. Assume an ideal gas is formed, that performs volume change work.
I've been able to calculate the ΔH, but I do not know how to calculate the ΔU. I know that I'm supposed to use
ΔU = q + w and PV = nRT, but I don't know how.