Chemical Equilibrium

Chapter 15

Introduction

Lets consider the catalytic methanation reaction

The Equilibrium Constant

Some equilibrium compositions for the methanation reaction

Example 

The Law of Mass Action

The manipulation rules of equilibrium constants

Heterogeneous Equilibria

Calculating Equilibrium Constants

Example

USING THE EQUILIBRIUM CONSTANT

we described how a chemical reaction reaches equilibrium.

how this equilibrium can be characterised by the equilibrium constant.

Applications of Equilibrium Constants

Predicting the direction of Reaction.

Calculating Equilibrium Concentrations

If Qc > Kc, the reaction will go left

If Qc < Kc, the reaction will go right

If Qc = Kc, the reaction is at equilibrium

Example

Three steps in solving equilibrium concentrations:

Set up a table of concentrations.

Substitute the expressions in x for equilibrium concentrations into the equilibrium constant expression.

Solve the equilibrium constant expression for the values of the equilibrium concentrations.

Changing the Reaction Conditions:

Le Chatelier’s Principle

Change in Reactant or Product Concentrations

Effects of Volume and Pressure Changes

Example

The Effect of Catalyst

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