Chemistry Chapter 13

Question 1

Macroscopically, concentrations at equilibrium seem to be…

Answer 1

static

Question 2

Microscopically, concentrations at equilibrium are…

Answer 2

1. moving frantically
2. have no net change

Question 3

What’s the forward rate?

Answer 3

Reactants turning into products.

Question 4

What’s the reverse rate?

Answer 4

Products turning into reactants.

Question 5

What are the characteristics of chemical equilibrium?

Answer 5

1. The forward and reverse rates are the same.
2. The forward and reverse reactions move towards eq. at an undetectable (slow) rate

Question 6

At equilibrium, forward rate…

Answer 6

equals reverse rate

Question 7

What’s the librium expression?

Answer 7

K = [C]^c[D]^d/[A]^d[B]^b
K is the eq. constant

Question 8

What’s the Haber process?

Answer 8

The process of creating ammonia using nitrogen and hydrogen.

Question 9

Each set of equilibrium concentrations is called…

Answer 9

an equilibrium position.

Question 10

What are the equations you can use when finding the pressure of a gas?

write them down on a sticky note

Answer 10

PV = nRT
P = (n/V)RT = CRT
C = n/V

Question 11

When finding the K in a heterogenous mixture, you must…

Answer 11

cancel out the solids and liquids.

Question 12

What’s the equation for finding K?

Answer 12

K = products/reactants

Question 13

What’s the equation for finding K’?
And what does it find?

Answer 13

K’ = Reactants/Products or 1/K
It’s the equilibrium reaction when the reaction is reversed.

Question 14

What’s the equation for finding K”?
And what does it find?

Answer 14

It finds the equilibirum constant of when the original reaction is multiplied by some factor (n).
K” = [C]^mn[D]^mn/[A]^mn[B]^mn
K’ = ([C]^m[D]^m/[A]^m[B]^m)^n
K” = K^n

Question 15

What’s the equation for molar concentration? (Also known as molarity.)

Answer 15

M = n/V
n: moles
V: volume

Question 16

What does the equilibrium constant for a reaction (K) help us predict?

Answer 16

1. the tendancies needed for the reaction to occur (not speed)
2. whether the concentrations represent an equilibrium condition
3. the equilibrium position that will be achieved from a given set of initial concentrations.

Question 17

What are the tendencies that you can infer from an equilibrium reaction (K)?

Answer 17

If K>1, there are more products in the equilibrium state of the reaction.
If K<1, there are more reactants in the equilibrium state of the reaction.

Question 18

The equilibrium constant also helps predict the direction in which a reaction will proceed to reach equilibrium from a given set of initial concentrations.
What directions can we predict that the reaction will need to go to achieve equilibrium given Q/a set of initial concentrations and K?

Answer 18

Q>K:
The reaction favors the products, and will have to shift towards the reactants.
Q<K:
The reaction favors the reactants, and will have to shift towards the products.
Q=K:
The reaction is an equilibrium.

Question 19

Calculate the equilibrium pressure of NO2 when N2O4 was found to be 2.71 atm, and when Kp= 0.133

N2O4 -><- 2NO2

Answer 19

PNO2 = 0.600 atm

Question 20

Solve page 526, example 13.9.

Answer 20

Answer is in the book.

Question 21

Solve example 13.11 page 530

Answer 21

Answer is in the book.

Question 22

What are the steps in solving equilibrium problems?

Answer 22

1. Balance the equation
2. Write the equilibrium expression using the law of mass action
3. List the initial concentrations
4. Calculate Q, and determine the direction of the shift to equilibrium
5. Define the change needed to reach equilibrium, and define the equlibrium concentrations by applying the change to initial concentrations. (ICE table.)
6. Substitute the equilibrium concentrations into the equilibrium expression, and solve for the unknown (whether it be K, or an eq. concentration.)
7. Check your calculated equilibrium concentrations by making sure they give the correct value of K.

Question 23

Solve page 531

Answer 23

Answer in the book

Question 24

solve page 553

Answer 24

in book

Question 25

What does Le Chatelier’s Principle state?

Answer 25

If a change is imposed on a system at equilibrium, the position of the equilibrium will shift in a direction that tends to reduce that change.

Question 26

What happens if you add a certain amount of a concentration to a reaction system that’s at equilibrium?

Answer 26

The reaction will shift to whatever direction is needed to remove the excess concentration.

Question 27

What happens if you remove a certain amount of a concentration to a reaction system that’s at equilibrium?

Answer 27

The reaction will shift to whatever direction is needed to synthesize the removed concentration.

Question 28

What happens when you add an inert gas (a gas not needed in the reaction) into the reaction system?

Answer 28

No effect on the concentrations or partial pressure of the reactants or products.

Question 29

If we decrease the volume of the container holding a gaseous system, what happens to the overall volume of the reaction system?

Answer 29

The system responds by decreasing its own volume, specifically of the total number of gaseous molecules.

Question 30

Solve page 538 example 13.13

Answer 30

in the book

Question 31

The addition of a reactant shifts the…

Answer 31

equilibrium position, not the constant.

Question 32

The value of K changes with…

Answer 32

temperature.

Question 33

N2(g)+3H2(g)-><-2NH3(g) + 92kJ
In which direction will this reaction go if it is heated?

Answer 33

To the left.