equilbrium FINISH WITH NOTES

Question 1

What happens when a reversible reaction reaches equilibrium?

Answer 1

The rate of forward and reverse reactions are equal

Question 2

Define the term dynamic equilibrium

Answer 2

When a reversible reaction is in a closed system, when equilibrium is a achieved, the rate of forward and reverse reactions are the same

Question 3

What is Le Chatelier Principle

Answer 3

For a reaction in dynamic equilibrium, if a change is imposed on the system, the equilibrium shifts to oppose the change

Question 4

What can Le Chatelier Principle be used to explain?

Answer 4

Le Chatelier’s principle can be used to predict the effects of changes in temperature,
pressure and concentration on the position of equilibrium in homogeneous reactions

Question 5

What happens to the position of an equilibrium if pressure is increased?

Answer 5

The equilibrium shifts to the side of the reaction with less number of gaseous moles

Question 6

What happens to the position of an equilibrium if temperature is increased?

Answer 6

The equilibrium shift to the endothermic direction to reduce temperature

Question 7

What happens to the position of an equilibrium if the concentration of a reactant is increased?

Answer 7

The equilibrium shifts to the products to remove the added reactants

Question 8

How does the addition of a catalyst affect a reaction at
equilibrium?

Answer 8

Does not affect the position of equilibrium, but speeds up the rate at which equilibrium is achieved

Question 9

What information shows if a reaction is exothermic or
endothermic?

Answer 9

Reactions at equilibrium are shown with a value for H for the forward direction

• H indicates forward reaction is exothermic (and therefore reverse is endothermic)

+ H indicates forward reaction is endothermic (and therefore reverse is exothermic)

Question 10

How are concentrations shown in a Kc expression?

Answer 10

[ ] (inside square brackets)

Question 11

How is a Kc expression formulated?

Answer 11

(concentration terms are raised to the power of the balancing number and then
multiplied)

Question 12

What factors affect the value of Kc ?

Answer 12

temperature

Question 13

A reaction is exothermic in the forward direction. What happens to
the value of K c if:
a) temperature is increased?
b) temperature is decreased?

Answer 13

a) If temperature is increased the reaction shifts in the endothermic direction
(backwards), therefore Kc decreases

b) If temperature is decreased the reaction shifts in the exothermic direction (forwards),
therefore Kc increases