Chapter 15 - Chemical Equilibrium

Question 1

Define chemical equilibrium.

Answer 1

when a reaction and its reverse reaction proceed at the same rate

Question 2

As a system approaches equilibrium, _______________ are occurring.

Answer 2

both the forward and reverse reactions

Question 3

At equilibrium, the forward and reverse reactions are proceeding _____________.

Answer 3

at the same rate

Question 4

Once equilibrium is achieved, the amount of each reactant and product _______________.

Answer 4

remains constant

Question 5

What does ⇌ denote in a reaction equation?

Answer 5

that it is an equilibrium reation

Question 6

Define K eq.

Answer 6

the expression for the equilibrium constant

Question 7

Define the Haber Process.

Answer 7

the industrial preparation of ammonia

Question 8

Define K c.

Answer 8

an equilibrium constant in terms of molar concentration

Question 9

Define K p.

Answer 9

an equilibrium constant in terms of partial pressure

Question 10

What is the equilibrium expression for the generalized reaction a A + b B ⇌ d D + e E.

Answer 10

K c = [D]^d[E]^e / [A]^a[B]^b

Question 11

What do [D]^d[E]^e denote in the equilibrium expression K c = [D]^d[E]^e / [A]^a[B]^b ?

Answer 11

the products

Question 12

What do [A]^a[B]^b denote in the equilibrium expression K c = [D]^d[E]^e / [A]^a[B]^b?

Answer 12

the reactants

Question 13

How can equilibrium be expressed in terms of partial pressure?

Answer 13

K p = (P D)^d(P E)^e / (P A)^a(P B)^b

Question 14

What does the expression K p = K c (RT)^ Δn indicate?

Answer 14

(equilibrium constant in terms of partial pressure) = (equilibrium constant in terms of molar concentration) [(ideal gas constant)(absolute temperature of the gas)] ^ [(moles of gaseous product)-(moles of gaseous reactant)]

Question 15

What is indicated if K&raquo_space; 1?

Answer 15

the reaction favors products; products predominate at equilibrium

Question 16

What is indicated if K &laquo_space;1?

Answer 16

the reaction favors reactants; reactants predominate at equilibrium

Question 17

The equilibrium constant of a reaction in the reverse reaction is the (same/reciprocal) of the equilibrium constant of the foreward reaction.

Answer 17

reciprocal

Question 18

To find the new equilibrium constant of a reaction when equation has been multiplied by a number, _________.

Answer 18

raise the original equilibrium constant to that power

Question 19

When two consecutive equilibria occur, the equations can be ______________.

Answer 19

added to give a single equilibrium

Question 20

The equilibrium constant of the equation derived by adding two consecutive equilibrium equations is the ________ of two constants.

Answer 20

product

Question 21

Define homogeneous equilibria.

Answer 21

occurs when all reactants and products are in the same phase

Question 22

Define heterogeneous equilibria.

Answer 22

occurs when something in the equilibria is in a different phase

Question 23

The value used for the concentration of a pure substance is always ____.

Answer 23

1

Question 24

How are equilibrium concentrations deduced?

Answer 24

1. Tabulate all known initial and equilibrium concentrations.
2. For anything for which initial and equilibrium concentrations are known, calculate the change.
3. Use the balanced equation to find change for all other reactants and products.
4. Use initial concentrations and changes to find equilibrium concentration of all species.
5. Calculate the equilibrium constant using the equilibrium concentrations.

Question 25

Define LeChâtelier’s Principle.

Answer 25

“If a system at equilibrium is disturbed by a change in temperature, pressure, or the concentration of one of the components, the system will shift its equilibrium position so as to counteract the effect of the disturbance.”

Question 26

If the system is in equilibrium, adding a reaction component ______________.

Answer 26

will result in some of it being used up

Question 27

If the system is in equilibrium, removing a reaction component ____________.

Answer 27

will result in some of it being produced

Question 28

When gases are involved in equilibrium, a change in ___________ will affect equilibrium.

Answer 28

pressure or volume

Question 29

Higher ______ or lower _______ favors the side of the equation with more moles.

Answer 29

volume, pressure

Question 30

How does heat affect an endothermic reaction in equilibrium?

Answer 30

it acts like a reactant, driving the reaction to favor products

Question 31

How does heat affect an exothermic reaction in equilibrium?

Answer 31

it acts like a product, driving the reaction to favor reactants

Question 32

What is the one instance in which a system in equilibrium can be affected by a catalyst?

Answer 32

the Haber Process

Question 33

Why can the equilibrium of the Haber Process be affected by a catalyst?

Answer 33

the activation energy required for the reaction is quite high

Question 34

How do catalysts affect the forward and reverse reactions of a system?

Answer 34

they increase the rate of both the forward and reverse reactions

Question 35

In the presence of a catalyst, _________ is achieved faster, but the ___________ remains unaltered.

Answer 35

equilibrium, composition

Question 36

In the presence of a catalyst, ___________ is lowered, allowing ___________ to be established at a lower temperature.

Answer 36

activation energy, equilibrium