Consider the following reactions :
(i) H⁺_(aq) + OH^$$-$$_(aq) = H₂O_(l),  $$\Delta $$H = $$-$$ X₁ kJ mol^$$-$$1
(ii) H_2(g) + 1/2O_2(g) = H₂O_(l),   $$\Delta $$H = $$-$$ X₂ kJ mol^$$-$$1
(iii) CO_2(g) + H_2(g) = CO_(g) + H₂O_(l),  $$\Delta $$H = $$-$$ X₃ kJ mol^$$-$$1
(iv) C₂H_2(g) + 5/2O_2(g) = 2CO_2(g) + H₂O_(l),    $$\Delta $$H = +X₄ kJ mol^$$-$$1

Enthalpy of formation of H₂O_(l) is

Given that bond energies of H $$-$$ H and Cl $$-$$ Cl are 430 kJ mol^$$-$$1 and 240 kJ mol^$$-$$1 respectively and $$\Delta $$H_f for HCl is $$-$$ 90 kJ mol^$$-$$1, bond enthalpy of HCl is

Assume each reaction is carried out in an open container. For which reaction will $$\Delta $$H = $$\Delta $$E ?

Identify the correct statement for change of Gibb's energy for a system ($$\Delta $$G_system) at constant temperature and pressure.