Question

Explain the difference between ΔH and ΔU.

Answer 1

delU= change in internal energy

Internal energy is the energy possessed by the molecules making up the substance. Change in internal energy can take placefrom understanding of first law of thermodynamcis which can be written as

delU = Q+W

Q= heat added to system ( if its removed it is -ve) and W= work done on the system ( it is -ve if system does work)=-PdV

delU+PdV= W

change in enthalpy (delH) is change in total energy of the system   and enthalpy H can be written as

H= U+PV

delH= delU+PdV+VdP

but ,delH= Q+VdP