10: Equilibrium I

Question 1

What is a reversible reaction?

Answer 1

Products break down into reactants

Mixture is present

Question 2

What is an irreversible reaction?

Answer 2

All reactants turn into products

Question 3

What is the formation of products called in equilibrium?

Answer 3

Forward reaction

“left to right”

Question 4

What is the formation of the reactants called in equilibrium?

Answer 4

Backward reaction

“right to left”

Question 5

What does dynamic equilibrium mean?

Answer 5

Dynamic - forward and backward reactions are constantly occurring, rates are equal
Equilibrium - no net change to amounts of reactant and product

Question 6

What are all reversible reactions assumed to occur in?

Answer 6

A closed system

Question 7

What is the term if more reactant is present at equilibrium?

Answer 7

Equilibrium lies to the left-hand side

Question 8

What is the term if more product is present at equilibrium?

Answer 8

Equilibrium lies to the right-hand side

Question 9

What is Le Chatelier’s principle?

Answer 9

When a change is applied to a system in dynamic equilibrium, the equilibrium shifts to oppose the change

Question 10

What happens if the conc of the reactant is increased/ conc of product decreases?

Answer 10

Equilibrium shifts to the right

Question 11

What happens if the conc of the reactant decreases / conc of product increases?

Answer 11

Equilibrium shifts to the left

Question 12

How does increasing pressure affect a system in equilibrium ?

Answer 12

Equilibrium shifts to the side with fewer moles of gas

Question 13

How does decreasing pressure affect a system in equilibrium ?

Answer 13

Equilibrium shifts to the side with most moles of gas

Question 14

How is enthalpy related in reversible reactions?

Answer 14

Enthalpy value in forward reaction is equal and opposite to that of the backwards reaction
One is exothermic, the other endothermic

Question 15

If the forward reaction is exothermic, what affect will increasing/decreasing the temperature have?

Answer 15

Increased - equilibrium shifts to the left

Decreased - equilibrium shifts to the right

Question 16

If the forward reaction is endothermic, what affect will increasing/decreasing the temperature have?

Answer 16

Increased - equilibrium shifts to the right

Decreased - equilibrium shifts to the left

Question 17

What is the main reaction in the Haber process?

Answer 17

N2 + 3 H2 -> 2 NH3

All gas

Question 18

What is the enthalpy of the forward reaction of the Haber process?

Answer 18

-92 kJ/mol

Question 19

Where are the reactants found for the Haber process?

Answer 19

Hydrogen - natural gas

Nitrogen - atmosphere

Question 20

What are the conditions of the Haber process?

Answer 20

Nitrogen to hydrogen in 1:3 ratio
~400 C
200 atm
Iron catalyst
Unreacted reactants are recycled

Question 21

What are the compromises of the conditions of the Haber process?

Answer 21

High yield of ammonia (shifts equilibrium)
Produces it quickly (decreases time to reach equilibrium)
Economic considerations

Question 22

What does the temperature (~400C) in the Haber process do?

Answer 22

Low temp - as forward reaction is exothermic
Increases rate of reaction
Compromise - reduces yield of ammonia but decreases production time

Question 23

What does the pressure (200 atm) in the Haber process do?

Answer 23

High pressure - favours forward reaction (more ammonia)

Compromise - not as high as possible as its expensive

Question 24

What does the catalyst (iron) in the Haber process do?

Answer 24

No affect on equilibrium

Increases rate of reaction

Question 25

What is a stoichiometric power?

Answer 25

Means number of molecules in the equation

Big number in front of molecule

Question 26

What is Kc?

Answer 26

Equilibrium constant
At a given temperature
Only gases, aqueous

Question 27

What is the Kc equation?

Answer 27

[C]^c x [D]^d
——————- = Kc
[A]^a x [B]^b

[A] [B} - product of conc of reactants
[C] [D] - product of conc of products
a b c d - number of molecules of each molecule

Question 28

What does a large Kc mean?

Answer 28

Higher conc of products than reactants at equilibrium

Question 29

What does a small Kc mean?

Answer 29

Higher conc of reactants than products at equilibrium

Question 30

What does a Kc value = 1 mean?

Answer 30

Roughly equal quantities of products and reactants at equilibrium