Unit 3

Question 1

What is equilibirium

Answer 1

The point in a reversible reaction where there is no change in the concentration of products and reactants
- (Forward & Reverse processes occur at the same rate)

Question 2

What occurs to the concentration and reaction rates after dynamic equilibrium is reached

Answer 2

Concentrations –> not changing (can be at different values)
Rates –> reactions in the forward/back are still occurring but at the same rate resulting in no change in concentration

Question 3

What is the difference between static and dynamic equilibrium?

Answer 3

Static: Forward/Reverse reactions are not occurring + concentrations are not changing (bodies are at rest)
Dynamic: Concentrations are the same rate but reaction is occurring at the same rate (can occur)

Question 4

Whats the difference between a closed & open system?

Answer 4

Closed: no matter is transferred, but energy is transferred
Open: Matter is transferred (reactants/products may be lost to the environment), energy can be transferred

Question 5

What is an example of open system in chemistry, vs closed?

Answer 5

A pot of boiling water, where with a lid open, the water –> steam gets lost since gas moves away
Where lid is CLOSED –> the product (steam) cannot escape and condensates

Question 6

What is the relation between closed and open system and dynamic equilbirium/static

Answer 6

Dynamic equilibrium can only occur in a CLOSED SYSTEM, because if it was open, the products could escape (if R–>P(gas)
Wheares static is usually open system here it escapes and then no rate change occurs between reactants and products

Question 7

What is the collision theory

Answer 7

Particles can only react if they collide under the conditions of:
1. The minimum kinetic energy (or activation energy) is reached\
2. The correct orientation of the particle is reached

Question 8

What occurs to collision if concentration decreases and why?

Answer 8

Lower concentration means less successful collisions due to less reactant particles exist to react to form products.

Question 9

Define Le Chateliers Principle

Answer 9

For a system at dynamic equilibrium, if a change is made to the conditions of the reaction, the position of equilibrium with shift to counteract the change.

Question 10

Where does equilibrium shift if the temperature of a system is increased, and why?

Answer 10

Shifts to the endothermic reaction
To absorb the extra heat, ultimately cooling down the reaction to counteract the increase

Question 11

Where does equilibrium shift if the temperature of a system is decreased, and why?

Answer 11

Shifts to the exothermic reaction
By producing more heat and increase the temp again to counteract the decrease

Question 12

How does collision theory relate to the increase in temperature at equilibrium

Answer 12

The reaction rate favours the side with the highest activation energy required to react (usually the endothermic) –> since the largest change

Question 13

How does collision theory relate to the decrease in temperature at equilibrium

Answer 13

The reaction rate favours the side with the lowest activation energy required to react (usually the exothermic)

Question 14

In 2No2(g) –>/<– N2O4(g) (-ve,change in H), Where does a increase in temperature favour

Answer 14

Favours the endothermic reaction thus the reactants. Since to counteract the temp increase, the reaction favours the side which absorbs the extra added heat (endothermic = left = reactants)

Question 15

What occurs to the equilibrium of a system with an increase in the concentration of reactants and why?
A + B –>/<– C + D

Answer 15

Shifts equilibrium to the products
Le chattier, to counteract a change in conditions, wants to decrease concentration of reactants again by reacting them against each other and thus forming an increase in the concentration of products

Question 15

What happens to the concentration of liquids/solids/gases with a increase in the amount of each?

Answer 15

LIQUID/SOLID
Cant have concentration at liquid and solid
Thus changing the amount of liquid/solid present does not affect the position of equilibrium

GAS
Increases concentration

Question 16

What occurs to the equilibrium of a system with a decrease in the concentration of reactants and why?
A + B –>/<– C + D

Answer 16

Shifts equilibrium to the reactants
Le chattier, to counteract a change in conditions, wants to decrease concentration of products again by reacting them against each other and thus forming an increase in the concentration of reactants

Question 16

What occurs to the equilibrium of a system with a decrease in the concentration of products and why?
A + B –>/<– C + D

Answer 16

Shifts equilibrium to the products
Le chattier, to counteract a change in conditions, wants to increase concentration of products again by reacting reactants, forming an increase in the concentration of products again while decrease in reactants (used)

Question 16

What occurs to the equilibrium of a system with an increase in the concentration of products and why?
A + B –>/<– C + D

Answer 16

Shifts equilibrium to the reactants
Le chattier, to counteract a change in conditions, wants to increase concentration of reactants again by reacting products more forming an increase int he concentration of reactants again while decrease in products (used)

Question 17

How does collision theory relate to the increase in the concentration of the products at equilibrium

Answer 17

Can be for both reactants/products
Increase in products shifts to the reactants. The rate of the backward (to reactants) increases as the reverse reaction is dominant, due to a higher proportion of product particles collided compared to reactant, ultimately resulting in higher successful product collisions and hence rate backwards is higher.

Question 17

How does collision theory relate to the decrease in the concentration of the reactants at equilibrium

Answer 17

Can be for both reactants/products
Decrease in reactants shifts to the reactants. The rate of the backward (to reactants) increases as the reverse reaction is dominant, due to a higher proportion of product particles collided compared to reactant, ultimately resulting in higher successful product collisions and hence rate backwards is higher.

Question 18

How does collision theory relate to the increase in the concentration of the reactants at equilibrium

Answer 18

Can be for both reactants/products
Increase in reactant concentration shifts to the products. The rate of the forward (to products) increases as the forward reaction is dominant, due to a higher proportion of reactant particles collided compared to product, ultimately resulting in higher successful reactant collisions and hence rate forward is higher.

Question 18

What is the name of H3O+

Answer 18

Hydronium Ions

Question 18

What is a hydronium ion

Answer 18

H3O+

Question 18

What are the methods you can increase the pressure of a system (more gas in a smaller space)

Answer 18

1. Pump more of the same gasses (at the same concentrations) into the system 2. Decrease the volume of the system 3. Add an inert gas (since it won't react with anything) All of which result in more gas in a smaller space

Question 19

How much L does 1 mole of gas occupy

Answer 19

~ 24.79 (different for stuff)

Question 20

What occurs to a reaction in dynamic equilbiriumwhen gas is added to the system

Answer 20

Pressure increases (Kpa), according to le chateliers, to counteract the change it needs to decrease the pressure of the system --> shifts to the side with lower moles of gas (since if 2moles react to give 1 mole, less volume occupies)

Question 21

What occurs to a reaction at dynamic equilibrium when the volume of a container is increased.

Answer 21

Pressure decreases (Kpa), according to le Chateliers, to counteract the change it needs to increase the pressure of the system. --> shifts to the side with more moles of gas (since if 1 moles react to give 2 mole, more volume occupies)

Question 22

What occurs to the rate of reaction, in relation to the collision theory as a result of the increase of inert gas within the system 2NO2(g) -->/<-- 1N2O4(g)

Answer 22

Increases inert gas increases the Kpa pressure, le chatelier wants to decrease it by shifting to the side with less moles of gas (therfore shifts to forward reaction) COLLISSION THEORY Since 2:1 in gas moles, there is a increase in the reactant particles, more particles = more successful reactions thus a higher rate of reaction temporarily in reactants.

Question 23

What does a grdual change in the concentration for all products and reactants indicate in a concentration/time graph?

Answer 23

A change in temp (undoes equilibrium to set a new one)

Question 24

What does a spike in the concentration of 1 substance indicate in a concentration/time graph?

Answer 24

The increase/decrease in the concentration of a substance

Question 25

What does a spike in all concentrations indicate in a concentration/time graph?

Answer 25

A change in pressure (increase/decrease in pressure due to a change in volume or inert gas added)