Equilibrium and Acid Base 1

Question 1

what is the definition of equilibrium?

Answer 1

no observable changes in macroscopic properties (example: colour, concentration, temperature)

Question 2

what is phase equilibrium?

Answer 2

a single chemical substance existing in more than one phase in a closed system.

ex: a mix of ice and water at 0°C

Question 3

what is solubility equilibrium?

Answer 3

a single chemical solute interacting with a solvent substance, where excess solute is in contact with the saturated solution

ex: solid in the bottom of a saturated solution

Question 4

what is chemical reaction equilibrium?

Answer 4

several substances: the reactants and products of a chemical reaction

ex: dissociation of weak acids or bases in water

Question 5

Reactions are often __________ which means that not only are the products formed but the reactants can be formed

Answer 5

reversible

• we use a double arrow to show this relationship

Question 6

What two states can equilibrium be

Answer 6

static or dynamic

Question 7

static equilibrium meaning

Answer 7

no changes occuring at any level

Question 8

dynamic equilibrium meaning

Answer 8

the change one way is countered by an equal and opposite change the other way

Question 9

the rates for a forward and reverse reaction will proceed at different rates. They depend on what?

Answer 9

The concentration of the reactants and products
- the forward direction will initially be the fastest if we only have reactants A and B
- As the products C and D are formed, the reverse reaction will speed up and the forward reaction will slow down.
- At some point the rates of forward and reverse reaction become equal.

Question 10

a system is said to be in a state of dynamic equilibrium when?

Answer 10

1. The rates of the forward and reverse reactions are equal
2. The observable (macroscopic) properties of the system such as temperature, pressure, concentration, pH are constant
3. the system is closed at a constant pressure
4. The reaction must be reversible

Question 11

In a chemical equalibrium, the rate of the forward reaction is _____ to the rate of the reverse reaction!

Answer 11

equal

Question 12

what are the three classes of chemical equilibria?

Answer 12

1. reactants favoured (percent rxn < 50%)
2. products favoured (percent rxn > 50%)
3. quantitative to the right (percent rxn > 99%)

Question 13

what is the law of equilibrium

Answer 13

there is a constant ratio between the concentrations of the products and the concentrations of the reactants at the equilibrium

at a given temperature for a given reaction, an equilibrium constant (K꜀) will always be the same no matter what the initial concentrations of the species. This is useful because it allows us to predict the amount of a substance made even when we do not get a complete reaction

Question 14

K꜀ is constant for a reaction at a given ___________. If you change the temperature, K꜀ also changes

Answer 14

temperature

Question 15

When determining K꜀ use only the species that are in ___ or _______ states unless all states are the ____ then use them all

Answer 15

gas
aqueous
same

Question 16

the higher the value of K꜀, the greater the tendency for the reaction to favor the ________________

Answer 16

forward reaction (the products)

Question 17

If K꜀ is greater than 1, then the reaction is _________ favoured

Answer 17

products

Question 18

If K꜀ is less than 1, then the reaction is _________ favoured

Answer 18

reactants

Question 19

K꜀ indicates the ________________ and not the rate of reaction

Answer 19

Percent reaction

Question 20

catalysts will not affect the [] at equilibrium… _____________________________

Answer 20

they only increase the rate of rxn (by lowering activation energy)

Question 21

what is the three-step process of Le Chatelier’s principle?

Answer 21

1. initial equilibrium state
2. shifting non-equilibrium state
3. new equilibrium state

Question 22

what does le chatelier’s principle state?

Answer 22

When a chemical system at equilibrium is disturbed by a change in property of the system, the system adjusts in a way that opposes the change

a system can be affected by a change in concentration, temperature, and/or volume (pressure)

Question 23

In a concentration change of a system, what happens if the concentration increases vs decreases

Answer 23

An increase in the concentration of the products or reactants favours the other side of the equation

A decrease in the concentration of the products or reactants favours the same side of the equation

ex: N₂(g) + 3 H₂(g) ⇌ 2 NH₃(g)
↑ [N₂(g)] will shift the equilibrium to the products/to the right
↑ [NH₃(g)] will shift the equilibrium to the reactants
↓ [NH₃(g)] will shift the equilibrium to the products

Question 24

in a temperature change of a system, how is Kc affected by the transfer of temperature?

Answer 24

energy is treated like a reactant or product
a change in temperature is the only stress that will change the value of Kc!!
if the shift is toward the product side, Kc will increase
if the shift is towards the reactant side, Kc will decrease

ex:
reactants + energy ⇌ products
reactants ⇌ products + energy
- if cooled, equilibrium shifts so more heat is produced
- if heated, equilibrium shifts away from the heat so it cools down

Question 25

In volume and pressure changes of a system, with gases, volume and pressure are related (volume ____, pressure __)

Answer 25

down, up

Question 26

In volume and pressure changes of a system, the concentration of a gas is related to volume (volume ____, Concentration __)

Answer 26

down, up

Question 27

In volume and pressure changes of a system, an increase in concentration caused by a drop in volume causes a shift toward the side of the equation with _____ moles of gas

Answer 27

fewer
Example: N2(g) + 3 H2(g) ⇌ 2 NH3(g)
will shift to NH3(g)

Question 28

In volume and pressure changes of a system, if the number of moles are the same on both sides of the reaction, a change in volume has _________

Answer 28

no effect

Question 29

In volume and pressure changes of a system, changes in volume and pressure have _________ of value of Kc

Answer 29

no effect

Question 30

what does ICE stand for?

Answer 30

I = initial concentrations
C = change in concentrations
E = equilibrium concentrations

Question 31

what do we use to calculate equilibrium/initial concentrations of reactants or products?

Answer 31

Kc and ice tables

Question 32

what is the formula for percent reaction?

Answer 32

(equilibrium yield/maximum yield)*100

Question 33

what is the only stress that will change the value of kc?

Answer 33

a change in temperature

Question 34

Draw the graph for Dynamic Equilibrium

Answer 34

Question 35

Draw a graph to demonstrate the changes to equilibrium for the equation: N₂(g) + 3H₂(g) ⇌ 2NH₃(g) + energy for the following stresses:
a) Addition of H₂(g) c) Decrease in volume
b) the Addition of inert gas, the addition of catalyst d) an Increase in energy

Answer 35