Equilibrium

Question 1

What are the features of equilibrium?

Answer 1

• Rates of the backwards and forwards reactions are equal

- the number of moles of the product and reactant remain constant

Question 2

Was is Kc

Answer 2

The equilibrium constant - Kc = conc of products/ conc of reactants

K>1 means forward reaction is favoured and K<1 means reverse is favoured
Kc = +/- 1 means equilibrium mixture has more or less the same amounts of both reactants and products

Question 3

What is another expression of Kc?

Answer 3

Kf/Kr

Question 4

Tell me about pressure and Kc

Answer 4

PV = nRT 
Ptotal = sum of all pressures in a mixture of gas 

Concentration of a substance = P/nRT
Kp = Kc(RT)^n —-> in this case n is the difference between the sum of the product molecules and the reactant molecules

Question 5

Does direction of the reaction matter?

Answer 5

No, we will still end up with the same proportions of all the substances at equilibrium

Question 6

What are the properties of Kc?

Answer 6

• must be at a specific temperature and for a specific reaction
• if a reaction has many steps, use:
  [final products]
  ———————
  [initial reactants]
• if reactants double, Kc is squared
• Kc of the reactants = 1/(Kc of the products)

Question 7

What is Qc?

Answer 7

The REACTION QUOTIENT

Basically Kc when the reaction is NOT at equilibrium ie. at current conditions

Question 8

What slides Qc tell us?

Answer 8

QKc then the products are in excess and the reverse reaction is favoured

Question 9

What does a catalyst do?

Answer 9

Increases the rate of the forward and backward reactions achieving equilibrium faster but the composition at eq. is unchanged

Decreases activation energy thus decreasing the difference between the transition and initial states.