Rates & Equilibrium (1)

Question 1

Define Dynamic Equilibrium

Answer 1

State that is reached when the amount of reactants and products remain constant even though forward and reverse reactions are still occurring.

Question 2

During a dynamic equilibrium… What 3 properties occur during this?

Answer 2

1. Rate of forward and reverse reactions are equal
2. Concentration of all species are UNCHANGED
3. Macroscopic properties (temp. pressure + colour) are CONSTANT

Question 3

What is the formula of equilibrium constant?

Answer 3

K = P/R

Question 4

Define Le Chatelier’s Principle for adding or removing reactant/product

Answer 4

If a change is made to a system at equilibrium, the system will react to partially counteract the change and establish a new equilibrium

Question 5

Define Le Chatelier’s Principle for total pressure or volume change

• 2SO2 (g) + O2 (g) ⇌ 2SO3 (g)

Answer 5

• If the pressure was increased the system would shift in the way to reduce the total pressure and move in the direction of the fewest gas particles.
• An increase in pressure will cause a net forward reaction to occur in order to reduce the total pressure – increasing the concentration of SO3 (g) present in the equilibrium

Question 6

Define Le Chatelier’s Principle for temperature change

Answer 6

‘The forward reaction is an exothermic reaction.
The reverse reaction is an endothermic reaction.
Increasing temperature favours the endothermic reaction.
Therefore the reverse reaction would be favoured.’

• A change in temperature will lead to a change in the equilibrium constant for that reaction.
• In general an increase in temperature will favour the endothermic reaction.
• A decrease in temperature will favour the exothermic reaction.

Question 7

What is the difference between an open and closed chemical system?

Answer 7

Open: Allow matter and energy to be exchanged with surroundings
Closed: Allow energy but not matter to be exchanged with surroundings

Question 8

How do you determine if a reaction can undergo reversibility?

Answer 8

• reversibility of chemical reactions is dependent on the activation energies of both the forward and reverse reactions.
• Once the products form it is possible for the reverse process to occur.
• If the newly formed product particles collide with enough energy to break their bonds (equal to the activation energy of the reverse reaction) then it is possible to reform the original reactants.