If the bond dissociation energies of XY, X₂ and Y₂ (all diatomic molecules) are in the ratio of 1:1:0.5 and $$\Delta H_f$$ for the formation of XY is -200 kJ mole^-1. The bond dissociation energy of X₂ will be :

An ideal gas expands in volume from 1$$\times$$10^-3 m³ to 1 $$\times$$ 10^-2 m³ at 300 K against a constant pressure of 1$$\times$$10⁵ Nm^-2. The work done is :

The enthalpies of combustion of carbon and carbon monoxide are -393.5 and -283 kJ mol-1 respectively. The enthalpy of formation of carbon monoxide per mole is :

The internal energy change when a system goes from state A to B is 40 kJ/mole. If the system goes from A to B by a reversible path and returns to state A by an irreversible path what would be the net change in internal energy?