Q20.31 P - Chemistry: Molecular Nature Of Matter And Change

Question

Describe the equilibrium condition in terms of the entropy changes of a system and its surroundings. What does this description mean about the entropy change of the universe?

Step-by-Step Solution

Answer

The universe's net entropy change is zero once it reaches equilibrium.

Step 1: Entropy.

Entropy is the thermodynamic function that represents the degree of disorderness of a system. For a spontaneous process the sign pf entropy is positive. 

Step 2: Explanation.

The spontaneous process may be characterized as a rise in the entropy of the surroundings inside a reduction in the entropy of the system, according to the second law of thermodynamics.  ${\mathrm{\Delta S}}_{\mathrm{univ}}>0$ as the chemical reaction or process approaches equilibrium.

When you approach equilibrium, the forward reaction rate equals the backward reaction rate, and the forward reaction's entropy change equals the backward reaction's entropy change.

The net change in entropy is zero in an equilibrium state, hence ${\mathrm{\Delta S}}_{\mathrm{univ}}>0$  because the system's entropy change is balanced by the entropy change in the environment.

 $\begin{array}{c}{\mathrm{\Delta S}}_{\mathrm{univ}}={\mathrm{\Delta S}}_{\mathrm{sys}}+{\mathrm{\Delta S}}_{\mathrm{surr}}\\ =0\\ {\mathrm{\Delta S}}_{\mathrm{sys}}=-{\mathrm{\Delta S}}_{\mathrm{surr}}\end{array}$

Therefore, universe's net entropy change is zero when it reaches equilibrium.