Question

Sketch qualitatively accurate graphs of G vs. P for the three phases of H20 (ice, water, and steam) at 0°C. Put all three graphs on the same set of axes, and label the point corresponding to atmospheric pressure. How would |the graphs differ at slightly higher temperatures?

Short answer

As the temperature rises above 0°C, the ice curve shifts to the left of the steam curve.

Step-by-step solution

Given information

From the thermodynamic potential from the Gibbs free energy at constant temperature, we have

${\left(\frac{\partial G}{\partial P}\right)}_{T,N}=V$

Where,

P is pressure

V is volume

We will use the above equation to draw the graph with slope $\frac{\partial G}{\partial P}$.

Explanation 

The graph below represents the three phases of H₂O at 0 degree temperature.

The ice graph is steeper than the water graph in this instance. The slope of steam is steeper than the graphs of ice and water. The compressibility of steam is greater than that of ice and water. As a result, it has a downward curvature, as indicated in the diagram above.

Explanation 

Gibbs free energy's temperature dependency is given as

${\left(\frac{\partial G}{\partial T}\right)}_{P.N}=-S$

Where,

G id Gibbs free energy

T is temperature

S is entropy of system

Using the preceding equation, the Gibbs free energy of H₂O will decreases during each phase. The steam phase of H₂O has a higher entropy than the water and ice phases. As a result, Gibbs free energy decreases more in the steam phase and less in the ice phase.

As the temperature rises above 0°C, the ice curve shifts to the left of the steam curve, as seen in the diagram.