Correct relation between change in enthalpy and change in internal energy is
ΔH=ΔU+ΔngRT
As we know,
ΔH=ΔU+PΔV....(i)
For an ideal gas
PV=nRT
For reactant, PVA=nART
For product, PVB=nBRT
Thus,
P(VB−VA)=(nB−nA)RTPΔV=ΔngRT......(ii)
Substituting (ii) in (i), we get
∴ΔH=ΔU+ΔngRT