7.4 Qualitative Changes To Equilibrium

Question 1

What happens when there’s a disturbance to equilibrium?

Answer 1

A new equilibrium will be established so that the rate of the forward reaction and reverse reaction is equal

Question 2

What can disturb an equilibrium?

Answer 2

Pressure, temperature, concentration, or a combination of these

Question 3

What is Le Chatelier’s Principle

Answer 3

When a chemical system at equilibrium is disturbed by a change in a property, the system will adjust to OPPOSE the change

Question 4

What did Chatelier discover

Answer 4

That changing a property of a system creates a temporary “non equilibrium” state in the system, before a new equilibrium is established

Question 5

How does ammonia synthesis use le Chatelier’s principle?

Answer 5

By increasing the pressure, equilibrium shifts to the right because it has fewer mols, so more ammonia is yielded

Question 6

What happens to a chemical system if you increase pressure? decrease?

Answer 6

• Increase: equilibrium shifts to side with fewer mols
• Decrease: equilibrium shifts to side with more mols

Question 7

What is an equilibrium shift

Answer 7

A change in concentration of reactants and products to restore an equilibrium state

Question 8

What happens if you remove reactants

Answer 8

Reaction shifts left

Question 9

What happens if you add reactants

Answer 9

Reaction shifts right

Question 10

Explain how in Fe + SCN <-> FeSCN more product can be yielded

Answer 10

By adding more of a reactant one at a time (for example SCN), it will combine with Fe to create more products and vice versa. Adding a reactant will shift the rxn to the right to yield more product.

Question 11

What happens if you remove a product

Answer 11

Reaction shifts right

Question 12

What happens if you add product

Answer 12

Reaction shifts left

Question 13

Define collision theory

Answer 13

Entities in a chemical system must collide to react

Question 14

What happens when you increase concentration of an entity according to collision theory

Answer 14

It will most likely collide with other entities since there is more present

Question 15

What kind of collisions can potentially contribute to a reaction

Answer 15

Collisions between reactant entities

Question 16

The more frequently collisions occur, the more likely a…

Answer 16

Reaction will take place

Question 17

What can collision theory tell us about a chemical reaction system

Answer 17

It can tell us how a system at equilibrium responds to changes in concentration

Question 18

More reactant added = (collision theory)

Answer 18

More successful collisions; forward reaction increases, reaction shifts right

Question 19

More product added = (collision theory)

Answer 19

More successful collisions; reverse reaction rate increases, reaction shifts left

Question 20

What does the rate of a chemical reaction reflect (collision theory

Answer 20

How often reacting entities are colliding (whether its reactants or products)

Question 21

If you increase the concentrations of the reactants, what happens to the rate of the forward reaction and how does the system compensate

Answer 21

The rate of the forward reaction increases, leading to more products yielded until the reverse reaction rate begins to increase until both rates are equal. The new equal rate is how the new equilibrium is established

Question 22

Why do chemical engineers use Le Chatelier’s principle

Answer 22

To get a reaction to shift right to yield more product

Question 23

How is Chatelier’s used in:
3NO2 + H2O <-> 2HNO3 + NO

Answer 23

Since nitric acid is very useful, NO gets removed by reacting it with O2. Since its a product, the system shifts right so that more desired nitric acid is yielded

Question 24

How is Chatelier’s used in:
CO + H2O <-> CO2 + H2

Answer 24

In the gasification of carbon, it creates usable hydrogen fuel. More reactants get added to maximize yield of H2

Question 25

How is Chatelier's used in: Hb + O2 <-> HbO2

Answer 25

In the lungs, there is a high concentration of oxygen so the reaction shifts right to form HbO2 which gets pumped to the body cells with low concentrations of oxygen. The reaction shifts left so that the oxygen is released from hemoglobin for body cells to use.

Question 26

How is oxyhemoglobin formed?

Answer 26

From oxygen binding to hemoglobin

Question 27

What happens if an endothermic reaction loses energy?

Answer 27

The reaction is losing a reactant, so rxn shifts left and energy is released

Question 28

What happens if an exothermic reaction loses energy?

Answer 28

The reaction is losing a product, so rxn shifts right to make more products

Question 29

What happens if an endothermic reaction gains energy?

Answer 29

Reactant was added, rxn shifts right

Question 30

What happens if an exothermic reaction gains energy?

Answer 30

Product was added, rxn shifts left

Question 31

What is an ideal gas?

Answer 31

A hypothetical gas: - made up of entities with no size - travels in a straight line - has no attraction to each other (no intermolecular forces) - obeys all gas laws

Question 32

What does Boyle's law state

Answer 32

As the volume of a gas changes, the pressure changes proportionally

Question 33

State example of Boyle's Law

Answer 33

In a bicycle pump, decreasing volume of gas in the cylinder to a third of its size increases the pressure threefold

Question 34

What is partial pressure

Answer 34

The pressure that a gas in a mixture of gases would exert if it occupied the whole volume alone

Question 35

All the pressure in a bicycle pump is...

Answer 35

the sum of the partial pressures of the gases in the cylinder

Question 36

In ammonia synthesis, which side has more partial pressure of gas and why

Answer 36

The reactants, because there is 4 mols on the reactants side and 2 on the products

Question 37

If you reduce the volume of a container involved in NH3 synthesis, which change in concentration would be greater? why?

Answer 37

The change in concentration of reactants will be greater because it has more mols

Question 38

If volume was reduced, where would equilibrium shift? What is the purpose of the equilibrium shift here?

Answer 38

Since pressure would increase, and pressure shifts reaction to the side with fewer mols, rxn shifts right to reduce pressure in the system

Question 39

Why would we want to change an equilibrium system without affecting equilibrium position? Is it possible?

Answer 39

For efficiency and productivity of yielding desired products. Despite limitations on how much concentration, pressure, and temp can be changed, it is possible.

Question 39

How does a catalyst change an equilibrium system without affecting equilibrium position

Answer 39

It increases the reaction rates of both the forward and reverse reaction so that products are yielded faster

Question 40

How does an inert gas change an equilibrium system without affecting equilibrium position

Answer 40

Since inert gases are unreactive it will not enter a chemical rxn. Adding an inert gas to a gas mixture (with constant volume) increases pressure to regulate the system. And, since equilibrium depends on partial pressures and an inert gas doesn't affect partial pressure, the equilibrium position is left unaffected.

Question 41

What is an inert gas

Answer 41

A noble gas with low reactivity since it has a full valence shell

Question 42

What happens to entities colliding with an inert gas? Does equilibrium shift?

Answer 42

It does not result in a chemical reaction but the inert gas can redirect the movement of the entity. The collision frequency of forward and reverse rxns remain unchanged so equilibrium does not shift

Question 43

How does the state of reactants affect equilibrium

Answer 43

Equilibrium can only be affected by concentrations of entities in the same states of matter as the substances in the system

Question 44

Why does solid iodine not have an affect on the equilibrium of:: H2 (g) + I2 (s) <-> 2HI (g)

Answer 44

We ignore solids and liquids when determining equilibrium because their concentrations are constant and do not affect the equilibrium expression.

Question 45

If K > 1, what is favored?

Answer 45

Products

Question 46

If K < 1, what is favored?

Answer 46

Reactants

Question 47

What happens to K if temperature increases in an endothermic reaction

Answer 47

K increases

Question 48

What happens to K if temperature increases in an exothermic reaction

Answer 48

K decreases

Question 49

What is the dependent variable

Answer 49

It is what's being affected in an experiment Example: When adding HCl to determine the affect on CuCl2, CuCl2 is dependent because it is being affected

Question 50

What is the independent variable

Answer 50

It is what's being changed in an experiment Example: When adding HCl to determine the affect on CuCl2, HCl is independent because we are testing its effect on CuCl2

Question 51

What's a control

Answer 51

The experiment setup without any changes

Question 52

What happens to a system with equal mols of gas on each side if volume is changed

Answer 52

Pressure cannot be changed, so equilibrium remains unaffected

Question 53

Are liquids and solids affected by pressure changes

Answer 53

No

Question 54

Which way does a reaction shift if you add a catalyst

Answer 54

No shift, catalysts don't affect equilibrium position