Unit 4- Equilibrium

Question 1

What is a dynamic equilibrium?

Answer 1

When a reaction reaches equilibrium the rate of the froward and backward reaction is equal and no further change in concentration occurs

Question 2

Write the Kc for the hydrogen - iodine reaction

Answer 2

H2 + I2 –> 2HI

Kc= [HI]^2/[H2][I2]

Question 3

What is the;

a) mole fraction
b) partial pressure

Answer 3

a) mole of substance/ total mole of equation
b) mole fraction x total pressure

The partial pressures must equal the total pressure

Question 4

Describe the relationship between the equilibrium constant and delta S system

Answer 4

Delta S system = RlnK

Question 5

Explain how temperature affects the Equilibrium constant?

Answer 5

increasing temperature for exothermic reactions- K decreases
Increasing temperature for endothermic reactions- K increases
Decreasing temperature for exothermic reactions - K increases
Decreasing temperature for endothermic reactions - K decreases

Question 6

How does pressure/volume affect an equilibrium?

Answer 6

Increase in pressure / Decrease in volume- favors reaction with less moles
Decrease in pressure/ Increase in volume - Favors reaction with more moles

Question 7

How does a catalyst affect equilibrium?

Answer 7

No affect on equilibrium
only increases rate of reaction
system reaches equilibrium quicker

Question 8

State and explain why the haber reaction has the conditions

Answer 8

Conditions are - 400 degrees, 200 atm, iron catalyst
If a small pressure is used, a small yield
Larger pressure gives a larger yield of ammonia
Low temperature means a slow rate of reaction
High temperature means an increased rate but decreases yield therefore medium temperature and catalyst used
High pressure is also expensive but needed to get an economical yield