for the real gases in reaction 2Co(g) +O2(g)-2CO2(g) ∆H=-560 kJ.In 10 L rigid vessel at 500K the initial pressure is 70 bar and after the reaction it becomes 50 barr. The change in internal energy is

We have,             ∆H          =             ∆U          +             ∆(PV)

=             ∆U          +             P2V2 – P1V1 —           —           (1)

As gases deviates from ideal gas behaviour, we cannot use,  ∆H                =             ∆U          +             ∆nRT

Thus                                      ∆(PV)    =             P2V2 – P1V1

=             40×1 – 70×1

=             – 30 L-atm

=             – 3.0 kJ

Therefore, by (1)             – 560     =             ∆U – 3.0

Therefore,                          ∆U          =             – 557 kJ