Equilibria

Question 1

How does temperature impact Kc/Kp for exothermic reactions?

Answer 1

For exothermic reactions:
Increase in temperature = Kc decreases
Decrease in temperature = Kc increases

Question 2

How does temperature impact Kc/Kp for endothermic reactions?

Answer 2

For endothermic reactions:
Increase in temperature = Kc increases
Decrease in temperature = Kc decreases

Question 3

What is the definition of dynamic equilibrium?

Answer 3

Where the rate of the forward and backwards reaction is the same, so the concentration of the reactants and products is constant

Question 4

Where can dynamic equilibria be reached?

Answer 4

Only in closed systems (i.e. nothing being added or leaving)

Question 5

What do you need to watch out for when finding the Kc of heterogenous reactions?

Answer 5

Solids and pure liquids should not be put into the Kc equation, as their concentrations are constant. Only add aqueous and gas species

Question 6

What is total pressure of a reaction?

Answer 6

All the partial pressures added together

Question 7

What does partial pressure equal in terms of mole fractions?

Answer 7

Mole fraction of a gas x Total pressure = Partial pressure

Question 8

How do you work out the mole fraction of a gas?

Answer 8

Number of moles of the gas / Total number of moles of gas in the mixture

Question 9

What is included in Kp expressions?

Answer 9

The partial pressures of products / The partial pressures of reactions (must all the be gases AT EQUILIBRIUM)

Question 10

What is the impact of changes in pressure on the value of Kp?

Answer 10

Pressure has no effect on the value of Kp

Question 11

What is the impact of a catalyst on the value of Kp?

Answer 11

Catalysts have no impact on the value of Kp, but rather speeds up the rate at which equilibrium is reached

Question 12

If the temperature changes forces equilibrium to shift to the right, what happens to the value of Kp/Kc?

Answer 12

The value of Kp/Kc increases

Question 13

If the temperature changes forces equilibrium to shift to the left, what happens to the value of Kp/Kc?

Answer 13

The value of Kp decreases

Question 14

What is the impact of changes in concentration on the value of Kc?

Answer 14

Changes in concentration have no impact on the value of Kc, as Kc is at equilibrium only, where the concentration of reactants and products is constant

Question 15

What is Qc?

Answer 15

Qc is essentially the same as Kc but can be found at any value, not just at equilibrium

Question 16

What is Qc as known as?

Answer 16

Reaction quotient

Question 17

How can you use Qc to help predict how a reaction will proceed and adjust to reach equilibrium?

Answer 17

You can compare the value of Qc to Kc.
For example Qc>Kc this indicated that the amount of product currently present (at Qc) is more than there would be at equilibrium (Kc), so you can predict that on the journey to equilibrium the reaction rid of some of the product.

Question 18

What does it mean if Qc=Kc?

Answer 18

The reaction is already at equilibrium