Chapter 11

Question 1

What is Kc?

Answer 1

Kc is the equilibrium constant

Question 2

What is the equilibrium constant calculated from?

Answer 2

The ratio of the product concentration compared to the reactant concentration

Question 3

For the reaction H2 + I2 –> 2HI, what is the equation for the equilibrium constant?

Answer 3

kc = (HI squared) / (H2 X I2)

Question 4

What does the definition of Kc only apply to?

Answer 4

Homogenous equilibria

Question 5

What is a homogenous equilibria?

Answer 5

An equilibria where all the products and reactants are in the same phase

Question 6

In a heterogenous equilibria, is everything included in the expression for Kc?

Answer 6

Not nececarily

Question 7

What don’t you include in the expression for Kc?

Answer 7

Solids or liquids

Question 8

Why don’t you include solids or liquids in the expression for Kc?

Answer 8

Because their concentrations stay constant throughout the reaction

Question 9

When calculating the value of Kc, what are the concentrations?

Answer 9

The concentration at equilibrium

Question 10

What will Fe2+ and Ag+ form an equilibrium with?

Answer 10

Fe3+ and Ag

Question 11

How can you work out the equilibrium constant of a reaction between Fe2+ and Ag+ ions?

Answer 11

Titrate them, to calculate the equilibrium concentration of Fe2+ ions. From this you can calculate the equilibrium concentrations of the other components, and Kc

Question 12

What do the square brackets represent in a Kc expression?

Answer 12

The square brackets represent the equilibrium concentrations

Question 13

What do the powers represent in a Kc expression?

Answer 13

The powers represent the number of moles of each substance

Question 14

What is the total pressure equal to?

Answer 14

The sum of the partial pressures

Question 15

What is a mole fraction?

Answer 15

The proportion of a gas mixture that is a particular gas

Question 16

What does the mole fraction of a gas in a mixture equal?

Answer 16

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

Question 17

What does the partial pressure of a gas equal?

Answer 17

Mole fraction of gas X total pressure of mixture

Question 18

What is Kp?

Answer 18

An equilibrium constant you can calculate when dealing with equilibria involving gases

Question 19

What is the difference between Kp and Kc?

Answer 19

With Kp you deal with partial pressures

Question 20

What is the unit of a partial pressure?

Answer 20

Atmosphere

Question 21

When calculating Kp for heterogenous equilibria, what does the calulation only involve?

Answer 21

Gases

Question 22

For a reaction where a solid S decomposes to form gases P and Q, what is the expression for Kp?

Answer 22

P(P)p(Q)

Question 23

When a reversible reaction reaches a dynamic equilibrium, what happens?

Answer 23

The forward reaction happens at the same rate as the backward reaction

Question 24

If you change the concentration, pressure or temperature of a reversible reaction, what are you going to do?

Answer 24

You are going to alter the position of the equilibrium

Question 25

What is Le Chatelier's principle?

Answer 25

If there's a change in concentration, pressure or temperature, the equilibrium will move to help counteract the change

Question 26

What does the greater the value of Kp or Kc mean?

Answer 26

The greater the value the further to the right the equilibrium lies

Question 27

What does the smaller the value of Kp or Kc mean?

Answer 27

The smaller the value the further to the left the equilibrium lies

Question 28

If the forward reaction is exothermic, and the temperature of the reaction is increased, what happens to the value of Kp?

Answer 28

The value of Kp decreases as there is less product

Question 29

If the backward reaction is endothermic, why does the position of the equilibrium shift to the left when the temperature is raised?

Answer 29

The equilibrium shifts to the left to absorb the extra heat

Question 30

As the value of the equilibrium constant is fixed at a given temperature, what happens if the concentration of one thing in the mixture changes?

Answer 30

The concentrations of the others must change to keep the value of Kc the same

Question 31

What does increasing the total pressure do?

Answer 31

It increases the partial pressures of each of the products and reactants

Question 32

Do catalysts effect the position of the equilibrium?

Answer 32

No, but they do mean an equilibrium can be reached faster