What is free energy change? Show that the change in free energy is equal to useful work done.
or
prove that –∆G = w(useful work)
Predict the enthalpy change, free energy change and entropy change when ammonium chloride is dissolved in water and the solution becomes colder.
At , ice and water are in equilibrium and  for the process  Calculate  for the conversion of ice to liquid water.
At equilibrium state,
       Â
  Â
For the reaction
calculate  at 700K when enthalpy and entropy changes are -113 kJ mol-1 and -145 JK-1 mol-1 respectively.
From the following values of ∆H and ∆S, decide whether or not these reactions will be spontaneous at 298 K:
Reaction A:
∆H = – 10.5 X 103 J mol–1
∆S = + 31 JK–1 mol–1
Reaction B:
∆H = – 11.7 X 103 J mol–1 ;
∆S = –105 jK–1 mol–1.