Statement (I): The Clapeyron equation enables us to determine the enthalpy change associated with phase change.

Statement (II): Using usual notations, the Clapeyron equation is given by \({\left( {\frac{{dT}}{{dP}}} \right)_{sat}} = \frac{{{h_{fg}}}}{{T{v_{Fg}}}}\)

Concept:

Clausius-Clapeyron equation:

Clausius-Clapeyron equation is a relationship between the enthalpy of evaporation, saturation pressure and temperature, and the specific volume of the two phases involved.

This equation can be derived from Maxwell equation:

\({\left( {\frac{{\partial P}}{{\partial T}}} \right)_v} = {\left( {\frac{{\partial s}}{{\partial v}}} \right)_T}\)

P is the pressure, T is the temperature, v is the specific volume and s is the specific entropy

During a phase change, the pressure and temperature are dependent properties

\({\left( {\frac{{dP}}{{dT}}} \right)_v} = {\left( {\frac{{ds}}{{dV}}} \right)_T}\)

During phase change \({s_{fg}} = \frac{{{h_{fg}}}}{{{T_{sat}}}}\)

\(\frac{{dP}}{{dT}} = \frac{{{s_g} - {s_f}}}{{{v_g} - {v_f}}} = \;\frac{{{h_{fg}}}}{{{T_{sat}}{v_{fg}}}}\)

This equation is useful to find out the latent heat (enthalpy change h_fg) at the change of phase for a given pressure.

Therefore statement II) is incorrect as it has represented the Clausius-Clapeyron equation in the wrong way.