Chapter 18, Problem 18.90QP

Interpretation Introduction

Interpretation:

The time during which the given event is observed should be calculated.

Concept Introduction:

Entropy is the measure of randomness in the system.  The entropy change in a reaction is the difference in entropy of the products and reactants.  ${\text{(ΔS}}_{\text{rxn}}\text{)}$ can be calculated by the following equation.

  ${\text{ΔS}}_{\text{rxn}}{\text{ = S}}_{\text{Products}}-{\text{ S}}_{\text{reactants}}$

Where,

  ${\text{S}}_{\text{reactants}}$ is the entropy of the reactants

  ${\text{S}}_{\text{Products}}$ is the standard of the products

Standard entropy change in a reaction and entropy change in the system are same.

Using the value for the change in enthalpy in a system and the temperature, we can calculate ${\text{ΔS}}_{\text{surr}}$ for an isothermal reaction.

${\text{ΔS}}_{\text{surr}}\text{=-}\frac{{\text{ΔΗ}}_{\text{sys}}}{\text{T}}$

The summation of ${\text{ΔS}}_{\text{sys}}$ and ${\text{ΔS}}_{\text{surr}}$ will give the value for the entropy change in the universe ${\text{(ΔS}}_{\text{univ}})$. If the ${\text{ΔS}}_{\text{univ}}$ is positive then the reaction will be spontaneous.  If the ${\text{ΔS}}_{\text{univ}}$ is negative, then the reaction is non-spontaneous.