Chapter 18, Problem 18.31QP

Interpretation Introduction

Interpretation:

Vapor pressure ($Kp$) of water has be calculated given gases phase reaction at ${25}^{°}C$.

Concept Information:

Thermodynamics is the branch of science that relates heat and energy in a system.  The laws of thermodynamics explain the fundamental quantities such as temperature, energy and randomness in a system.  Entropy is the measure of randomness in a system.  For a spontaneous process there is always a positive change in entropy. Free energy (Gibbs free energy) is the term that is used to explain the total energy content in a thermodynamic system that can be converted into work.  The free energy is represented by the letter G.  All spontaneous process is associated with the decrease of free energy in the system.  The equation given below helps us to calculate the change in free energy in a system.

$\text{ΔG = }\Delta {\rm H}\text{- T}\Delta \text{S}$

Where,

  $\text{ΔG }$ is the change in free energy of the system

  $\Delta {\rm H}$ is the change in enthalpy of the system

  $\text{T}$ is the absolute value of the temperature

  $\Delta \text{S}$ is the change in entropy in the system

Kp:  The equilibrium constant calculated from the partial pressures of a reaction equation. It is used to express the relationship between product pressures and reactant pressures. It is unites number, although it relates the pressures.

$\begin{array}{l}\text{Kp}\text{=}\text{Kc}{\text{(RT)}}^{\text{Δn}}\text{(or})\\ Kc=\frac{\text{Kp}}{{\text{(RT)}}^{\text{Δn}}}(or)Kp={\text{(RT)}}^{\text{Δn}}\\ \text{Δn}\text{=Product - Reactant}\end{array}$

Free energy$({\text{ΔG}}^0)$: In thermodynamics free energy or Gibbs free energy is the energy that is used to express the total energy content of a system.  According to second law of thermodynamics, in all spontaneous process is associated with the decrease in free energy of the system.  That is the change in free energy will be negative.

Vapour pressure: Vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in closed system.

Vapour pressure is nothing but the tendency of particles to escape from the liquid (or) solid.