Equilibrium

Question 1

What is Kc

Answer 1

equilibrium constant, has a fixed value at a specific temperature

Question 2

What is the equilibrium constant expression?

Answer 2

write it down on paper

Question 3

high value of Kc

Answer 3

equilibrium lies to right, favors production of products, reaction almost completed

Question 4

low value of Kc

Answer 4

equilibrium lies to left, favors reactants, reaction barely started

Question 5

What is the purpose of the constant Kc?

Answer 5

to inform us of the nature of equilibrium (where it lies). But, it doesn’t tell us how quickly the equilibrium state is reached

Question 6

If Q=Kc, Q>Kc, Q

Answer 6

• Q=Kc: equilibrium is reached
• Q>Kc: proceed to favor reactants, shift to left
• Q

Question 7

What is the value of Kc in an inverse reaction?

Answer 7

Kc’, 1/Kc, Kc-1

Question 8

What is the value of Kc in a multiple of a reaction?

Answer 8

Kc^x

Question 9

What is the value of Kc when the reaction coefficients are halved?

Answer 9

square root Kc

Question 10

What is the value of Kc when two reactions are added together?

Answer 10

Kc^i x Kc^ii

Question 11

What do industries use equilibrium for?

Answer 11

to determine conditions that will maximize the yield of a product

Question 12

evaporation

Answer 12

liquid to vapour state

Question 13

condensation

Answer 13

vapour to liquid

Question 14

dynamic equilibrium

Answer 14

forward and backward reactions are still occurring even though it doesn’t look like it

Question 15

Forward reaction

Answer 15

left to right, reactants to products

Question 16

Backward reaction

Answer 16

right to left, products to reactants

Question 17

Specific characteristics of equilibrium (5)

Answer 17

• dynamic
• achieved in closed system so no exchange of matter with surroundings
• concentrations of reactants and products remain constant because they’re being produced and destroyed at an equal rate
• no change in macroscopic properties because concentration is constant (color or density)
• can be reached from either direction

Question 18

Le Chatelier’s principle

Answer 18

system at equilibrium when subjected to a change will respond in such a way to minimize the effect of the change

Question 19

What happens when the concentration of a reactant increases?

Answer 19

• forward reaction increases, rate of reactions no longer equal
• at equilibrium, equilibrium favors production of products, shifts to right

Question 20

What happens when a product is removed or it decreases in concentration?

Answer 20

• backward reaction decreases, rate of reactions no longer equal
• equilibrium favors production of product, shift to right

Question 21

What happens when pressure is increased?

Answer 21

equilibrium shifted to side with smaller number of particles

Question 22

What happens when pressure is decreased?

Answer 22

equilibrium shifted to side with greater number of particles

Question 23

Exothermic reactions

Answer 23

• temperature always decreases
• enthalpy negative
• favors production of products, equilibrium shifts to right
• product particles don’t have enough energy to form bonds
• takes less energy to form bonds with products
• increased value of Kc

Question 24

Endothermic reactions

Answer 24

• temperature always increases
• enthalpy positive
• favors production of reactants
• equilibrium shifted to left
• decreased value of Kc
• takes less energy to break bonds than it does to make them

Question 25

Where does equilibrium shift for exothermic reactions?

Answer 25

to the right, higher yield of products at a lower temperature

Question 26

Where does equilibrium shift for endothermic reactions?

Answer 26

to the left

Question 27

Effect of concentration, pressure, temperature, catalyst on Kc

Answer 27

nothing changes the value except temperature

Question 28

What is one dilemma we come across with exothermic reactions?

Answer 28

at a lower temperature, there is a lower rate of reaction, and it takes longer to produce a high yield of products

Question 29

What does a catalyst do? How do they affect the equilibrium state?

Answer 29

- speeds of rate of reaction by providing alternate reaction pathway with a lower activation energy - not chemically changed after reaction - speed up attainment of equilibrium state by making products form faster

Question 30

Draw and label an energy diagram

Answer 30

Label: - Ea of forward and backward reaction - reactants and products

Question 31

At high temperatures, the _______ reaction is favored. At low temperatures, the ______ reaction is favored.

Answer 31

- high temp= endothermic | - low temp= exothermic

Question 32

At high temperatures, the _______ reaction is favored. At low temperatures, the ______ reaction is favored.

Answer 32

- high temp= endothermic | - low temp= exothermic

Question 33

What is the goal for industrial companies in their processes?

Answer 33

- high rate of reaction | - equilibrium lies to the right to produce high yield of products

Question 34

Draw the reaction the haber process is based upon.

Answer 34

N2+ 3H2 +_ 2NH3

Question 35

Is the forward reaction of the haber process exothermic or endothermic?

Answer 35

exothermic

Question 36

Three key things to know for the Haber process:

Answer 36

- reactants and products are gases - change in number of gas molecules as reaction proceeds - forward reaction is exothermic, backwards is endothermic

Question 37

How is concentration used to benefit industries? Haber process.

Answer 37

- nitrogen and hydrogen have 1:3 ratio | - ammonia is removed once it forms, causing equilibrium to shift to right to favor products

Question 38

How is pressure used to benefit industries? Haber process.

Answer 38

- because there are less molecules on the right than the left( 2 on right, 4 on left), favored by high pressure - more ammonia made - optimum pressure: 2 x 10^7

Question 39

Optimum pressure for haber process

Answer 39

2 x 10^7

Question 40

How is temperature used to benefit industries? Haber process.

Answer 40

- forward reaction exothermic, so favored by lower temperature - moderate temperature of 450 degrees

Question 41

Temperature of Haber process

Answer 41

450 degrees

Question 42

Catalyst of Haber process

Answer 42

iron with small amounts of aluminum and magnesium oxides

Question 43

Catalyst of Haber process

Answer 43

iron with small amounts of aluminum and magnesium oxides

Question 44

Write out the three steps of the Contact Process with equations.

Answer 44

1. Combustion of sulfur to form sulfur dioxide 2. Sulfur dioxide oxidizes to form sulfur trioxide. 3. Sulfur trioxide reacts with water to form sulfuric acid.

Question 45

Is the forward process of the Contact Process exothermic or exothermic?

Answer 45

exothermic

Question 46

Describe pressure of Contact Process to create sulfuric acid.

Answer 46

- 3 molecules on right and 2 on left, reaction favored by high pressure - equilibrium shifts to right - produces more sulfur trioxide - 2 x 10^5 Pa

Question 47

Describe temperature of Contact Process to create sulfuric acid.

Answer 47

- forward reaction exothermic | - moderate temperature of 450 degrees celsius

Question 48

Describe catalyst of Contact Process to create sulfuric acid.

Answer 48

Vanadium (V) Oxide

Question 49

Too low a temperature for processes does what?

Answer 49

increase the yield, but decrease the rate at which it produces yield

Question 50

What is the pressure of the Contact process?

Answer 50

2 x 10^5

Question 51

Pressure of methanol production

Answer 51

- 5-10 x 10^6 Pa - 3 to 1 molecules means high pressure will favor product - equilibrium shifts to right

Question 52

Temperature of methanol production

Answer 52

- forward reaction is exothermic | - 250 degrees celsius

Question 53

Catalyst of methanol production

Answer 53

- Cu - Zno - Al2O3