Chapter 7. Chemical Equilibrium

Question 1

What is

1. Homogeneous Equilibrium
2. Heterogeneous Equilibrium

Answer 1

1. System in which participating substances are in one phase only
2. System in which participating substances are present in different phases

Question 2

1. Position
   and
2. Shift in Equilibrium

Answer 2

Position of equilibrium refers to the relative proportion of products to reactants in an equilibrium mixture

Shift right means more product, therefore favour foward reaction
Shift left means more reactants, therefore favour backward reaction

Question 3

Le Chatelier’s Principle

Answer 3

Le Chatelier’s Principle states that when a system in equilibrium is subjected to a change in conditions which disturbs the equilibrium, the position of equilibrium will shift in a way so as to reduce that change

Question 4

Factors affecting equilibrium

Answer 4

1. Changes in concentration or partial pressure
2. Changes in total pressure (moles of gases)
3. Changes in temperature (favour exo/endo)
4. Presence of Catalyst (does not affect position of equilibrium, only enables the state of equilibrium to be reached more quickly)

Question 5

Define Equilibrium Law and what affects the equilibrium constant? Units of equilibrium constant?

Answer 5

The Equilibrium Law states that if a reversible reaction is allowed to reach equilibrium, the product of the concentrations of each product (raised to the appropriate powers) divided by the concentrations of each reactants (also raised to the appropriate power) has a constant value called the equilibrium constant K, at a constant temperature.

K is only dependent on temperature

Units of Kc = (mol/dm3)^c+d-a-b

Question 6

1. Difference between Qc and Kc. (reaction Quotient vs Equilibrium Constant)
   and
2. Using Qc to predict Direction of a Reaction

Answer 6

1. Kc is a subset of Qc. Qc can be taken from any point of the reaction. Kc is only at the equilibrium point.
2. Qc smaller than Kc - Reaction proceeds forward
   Qc = Kc - System is in Equilibrium
   Qc greater than Kc - Reaction proceeds backward

Question 7

Concerns of Haber Process and solutions

Answer 7

1. Kinetics problem - maximise rate of reaction
   Equlibrium problem - maximise yield
2. Rate is increased by using finely divided iron as catalyst. Increasing concentration of nitrogen and hydrogen

N^2(g) + 3H^2(g) ⇌ 2NH^3(g)

Yield is increased by employing a continuous flow process, where product ammonia is continuously removed as it forms

Question 8

Finding

1. Equilibrium concentration/pressure
2. Average Mr of equilibrium mixture

Answer 8

1. ICE Table

2. Partial pressure/total pressure * Mr (repeat for all substances involved in reaction)

Question 9

Writing equation for Kc and Kp

Answer 9

(Product of Reactants raised to appropriate powers)/(Product of products raised to appropriate powers)