Equilibria (Physical) (complete)

Question 1

Give the four conditions during a dynamic equilibrium reaction.

Give Le Chateliers Principle.

Answer 1

• Both reactions are taking place:
• simultaneously
• rate of forward and backward reactions are equal (and not zero)
• the concentrations of all substances are constant
• in a closed system
• If the conditions of a system at equilibrium are changed, the position of the equilibrium moves to oppose that change.

Question 2

Give the equation for Kc (equilibrium constant)
- (What happens if there are >1 mole of a certain substance present in the reaction?)

• What does a high vs low Kc value indicate about a reaction?
  (name the only factor affecting the Kc value of a reaction)

Answer 2

(product of concentrations of products) / (product of concentrations of reactant)

(if >1 mole of a certain substance present, put the concentration of that substance to the power of how many moles there are of it.)

• A high value means equilibrium position lies to the right, as a lot more product than reactant at equilibrium.
• A low value means equilibrium position lies to the left, as a lot more reactant than product at equilibrium.
• Temperature is the only factor affecting the Kc value of a reaction.

Question 3

Define Kc constant.
How would you calculate the units for Kc?

Answer 3

• A numerical way of showing the equilibrium position, and whether it ‘lies to the left or right’.
• write units out in full, factoring in for any ‘to the power of’s’. cancel out what can be cancelled, simplify what’s left. (may not be any units, so write ‘no units’)