(a) Reversible Process: It is defined as a system where change takes place infinitesimally slow and the direction of which at any point can be reversed by infinitesimal change in the state of the system.
(b) (i) For q = 0, heat is constant, so the process is adiabatic process.
(ii) For ∆U = 0, internal energy is constant which takes place at constant temperature, so, the process is isothermal process.
(iii) For ∆V = 0, volume is constant, so the process is isochoric process.
(iv) For ∆P = 0, pressure is constant, so the process is isobaric process.
(c) H2O(g) → H2 (g) + \(\frac{1}{2}\)O2(g);
∆rHΘ = 286.2 kJ mol−1
H2 (g) + \(\frac{1}{2}\)O2 (g) → H2O(s);
∆rHΘ = −286.2 kJ mol−1
It is referred to as first law of thermodynamics. According to this law, “energy can neither be created nor be destroyed but can be converted from one form to another"