The bond dissociation energies of X₂ , Y₂ and XY are in the ratio of 1 : 0.5 : 1. $$\Delta $$H for the formation of XY is –200 kJ mol^–1. The bond dissociation energy of X₂ will be

A gas is allowed to expand in a well insulated container against a constant external pressure of 2.5 atm from an initial volume of 2.50 L to a final volume of 4.50 L. The change in internal energy $$\Delta $$U of the gas in joules will be

For a given reaction, $$\Delta $$H = 35.5 kJ mol^$$-$$1 and $$\Delta $$S = 83.6 J K^$$-$$1 mol^$$-$$1. The reaction is spontaneous at (Assume that $$\Delta $$H and $$\Delta $$S do not vary with temperature.)

For a sample of perfect gas when its pressure is changed isothermally from p_i to p_f, the entropy change is given by