Q12.25P - Chemistry: Molecular Nature Of Matter And Change

Question

Use these data to draw a qualitative phase diagram for ethylene (${\mathbf{C}}_2{\mathbf{H}}_4$ ). Is  ${\mathbf{C}}_2{\mathbf{H}}_4$ (s) more or less dense than ${\mathbf{C}}_2{\mathbf{H}}_4$ (l)?

bp at 1 atm:  $\mathbf{-}\mathbf{103}\mathbf{.}{\mathbf{7}}^o\mathbf{C}$                          

mp at 1 atm:     $\mathbf{-}\mathbf{169}\mathbf{.}{\mathbf{16}}^o\mathbf{C}$         

Critical point:       $\mathbf{9}\mathbf{.}{\mathbf{9}}^o\mathbf{C}$      and  50.5 atm 

Triple point:           $\mathbf{-}\mathbf{169}\mathbf{.}{\mathbf{17}}^o\mathbf{Cand}\mathbf{1}\mathbf{.}\mathbf{20}\mathbf{\times }{\mathbf{10}}^{-3}\mathbf{atm}$   

                       

Step-by-Step Solution

Answer

The phase diagram of the ethylene compound  explained by the pressure vs temperature. The density of the solid is increases more than the liquid even after the critical point where solid-liquid density are equal.

Step 1: Phase Diagram

The phase diagram is the diagram which shows the change in phase. It tells about the change into all phases – Solid, Liquid and Gaseous.

It represents all the phases and transition are shown by the lines and the area between lines show the whole phase of the molecule.

 

The critical point can be explained as the point where the density of the different phases becomes equal. The critical point in which the volume of the two phases are the same at certain pressure and temperature.

 

The point can be said as the ‘Triple Point’ where all the three phases are in equilibrium the phases co-exist with each other.

 

Step 2: Graph Explanation

The graph is based on the different following data:

bp at 1 atm:      $\mathbf{-}\mathbf{103}\mathbf{.}{\mathbf{7}}^o\mathbf{C}$           

mp at 1 atm:    $\mathbf{-}\mathbf{169}\mathbf{.}{\mathbf{16}}^o\mathbf{C}$

Critical point:       $\mathbf{9}\mathbf{.}{\mathbf{9}}^o\mathbf{C}$       and 50.5 atm 

Triple point:    $\mathbf{-}\mathbf{169}\mathbf{.}{\mathbf{17}}^o\mathbf{Cand}\mathbf{1}\mathbf{.}\mathbf{20}\mathbf{\times }{\mathbf{10}}^{-3}\mathbf{atm}$

The phase diagram shows the Pressure vs Temperature of the Ethylene molecule showing the different phases – Solid, Liquid and Gaseous by the using the above data.