Unit 3: Equilibrium

Question 1

dynamic equilibrium

Answer 1

when opposing changes are occuring simultaneously at the same rate
- exists when the rate of the forward rection is equal to the rate of the reverse reaction

Question 2

forward reaction

Answer 2

read left to right in a chemical reaction. while reverse is read right to left

Question 3

conditions of all equilibrium systems

Answer 3

1. equilibrium is achieved in a reversible process when the rates of opposing changes are equal
2. the system is closed
3. the observable (macroscopic) properties of the system are constant though microscropic changes are taking place

Question 4

examples of chemical equilibrium systems

Answer 4

solubility
phase
chemical reaction

Question 5

solubility equilibrium

Answer 5

• dynamic equilirium in a close system between a solute and a solvent of a saturated solution
• rates of dissolving equals rate of cryslizqation

Question 6

saturated solution

Answer 6

one where the solvent has the maximum amount of solute issolved per unit volume

Question 7

phase equilibrium

Answer 7

between different physical states of a pure substance in a closed system
- rates of freezing equals rate of melting H2O(l) -> h2O(g) t=100degrees
- rate of condensation equal rate of evaporation

Question 8

chemical reaction equilibrium

Answer 8

between reactants and products of a chemical rection in a closed system
effective collsions between reactants to form products (forward reaction) equals the effective collisions between products to forms (reverse reaction)

Question 9

percent reaction

Answer 9

actual product yield at equilibrium/quantitative theoretical yield(stoichiometry) X100

Question 10

A system at equilibrium never

Answer 10

achieves completion , but rather there are always both reactants and products in the reaction mixture.

Question 11

what is the equilbirum constant used as

Answer 11

a quantitative measure to determine the amount of reactants and products present at equilibrium for a given chemical system

Question 12

is Keq temp dependant

Answer 12

YES

Question 13

kreverse

Answer 13

1/keqforward

Question 14

k»1

Answer 14

A higher [ ]+ of products and relatively low [ ]+ of reactants thus the eqbm favours the product side

Question 15

k=1

Answer 15

[ ] + of reactants and products is approx equal thus the eqbm does not favour one side over the other

Question 16

k«1

Answer 16

A higher [ ]+ of reactant and relatively low [ ]+ of products thus the eqbm favours the reactant side

Question 17

what does favous mean

Answer 17

the side of equation has higher numbers of moles and higher concentration than the other

Question 18

If keq is 1.0x10^10

Answer 18

has effectively gone to completion

Question 19

if keq is 1.0X10^-10

Answer 19

essentialy incomplete

Question 20

reaction quotient(Q)

Answer 20

concentration of products/ concentration of reactants

Question 21

ICE

Answer 21

initial concentration
change in concentration
equilibrium concentration

Question 22

whats le chateliers principle

Answer 22

when a chemical sytem at equilibrium is disturbedby an external stress which disprupts the equilibrium, the system adjusts in a way to oppose the change so as to restore equilibrium.

Question 23

external stresses on dynamic equilibrium systems

Answer 23

• concentration change
• temperature change
• pressure change with volume change
• addition of a catalyst
• addition of an inert chemical

Question 24

what happens when you increase the concentration of one or more of the reactants

Answer 24

the system will shift to the right (forward reaction accelerates)
**in order to create more product **

Question 25

what happens when you increase the concentration of one or more products

Answer 25

the system will shift to the left (reverse reaction accelerates) ***in order to create more reactants***

Question 26

is keq affected by changes in products or reactant

Answer 26

no because the ratio of products to reactants will remain tge same once dynamic equilibrium is restored

Question 27

for this equation CO2 + energy ⇌ 2CO + O2 what will happen when temperature is increased

Answer 27

the system will shift in the direction of the endothermic reaction and in this case to the right (accelerates forward reaction)

Question 28

why does it go toward the endothermic direction

Answer 28

the available thermal energy increases thus the reaction will absorb the excess heat(endothermic) and is then accelerated to remove

Question 29

for this equation: 2SO4 + O2 ⇌ 2SO3 + energy what will happen if the temperature is increased and decreased

Answer 29

increased will shift left and the reverse reaction will accelerate decreased it will shift right and the forward reaction will accelerate(direction of exothermic)

Question 30

why does it go in the exothermic direction

Answer 30

available thermal energy has decreased, thus the resction when releases heat (exothermic) is accelerated to replenish

Question 31

the concentration of a gas in a container is

Answer 31

inversibliy proportional to the volume of the container and directly proportionl to the pressure inside the container

Question 32

what happens if u decrease the volume of a container(increase in pressure and concentration)

Answer 32

will shift in the reaction direction which produces fewer molecules; thereby relieving pressure

Question 33

what happens if the volume of container is increased (decrease in pressure and concentration)

Answer 33

will shift in the reaction direction which produces more molecules; thereby increasing pressure

Question 34

what happens with the addition of an inert gas

Answer 34

nothing

Question 35

why does an inert gas have no affect

Answer 35

the inert gas does not react with any chemical entity in the system but rather simply takes up space therby altering the pressure but not the concentration of the chemical entities in the system

Question 36

addition of a catalyst

Answer 36

decreases the time required for the chemical system to reach equilibrium (due to lowering the required activation energy for bpth the forward and reverse reaction) but does not affect the final positin of the equilibrium.

Question 37

solubility equilibria

Answer 37

dynamic equilibrium between a solute and a solvent in a closed system - involves a heterogenous equilibrium (oe. more than one phase present)

Question 38

solubility product (ksp)

Answer 38

a special case of equilibrium that exists when excess solute is present in a saturated solution (deals with slighlty insoluble solutes)

Question 39

Qsp

Answer 39

equilibrium is achieved by moving to the right and thus still room for ions to dissolve unsaturated solution

Question 40

Qsp = Ksp

Answer 40

system is at eqbm and no more solute can dissolve and no precipitate formation saturated solution

Question 41

Qsp>ksp

Answer 41

eqbm is achieved by moving to the left and precipitate forms

Question 42

according to the arrhenius theory whats an acid

Answer 42

a molecular substance that ionizes in water to release hydrogen ions, Ex. H2SO4 -> 2H +SO4

Question 43

according to the arrhenius theory whats a base

Answer 43

an ionic substance that dissociates in water to release hydroxide ions Ex. NaOH -> Na + OH

Question 44

according to the bronsted-lowry theory whats an acid

Answer 44

a substance capable of donating a hydrogen ion (proton) to another "proton donor"

Question 45

according to the bronsted-lowry theory whats a base

Answer 45

a substance capable of accepting a hydrogen ion (proton) from another "proton acceptor"

Question 46

amphoteric

Answer 46

substance capable of acting as an acid or base in different chemical reactions ex. water

Question 48

weak acid

Answer 48

an acid that partially ionizes (<50%) in H2O to release hydronium, so exists primarily in the form of molecules.

Question 49

strong base

Answer 49

an ionic hydroxide that dissociates completely (<99%) in H2O to release hydoreixide ions ex. SrOH2 -> Sr + 2OH

Question 50

weak base

Answer 50

a substance that ionizes partially in H2O to form hydroxide ions, so primarily exists in the form of molecules

Question 51

kw

Answer 51

= ka x kb

Question 52

formula for pH

Answer 52

ph=-log[H3O]

Question 53

formula for pOH

Answer 53

pOH=-log[OH]

Question 54

formula for hydroxide concentration

Answer 54

[H3O] = 10^-pH

Question 55

formula for [OH]

Answer 55

[OH]= 10^-pOH

Question 56

the stronger an acid

Answer 56

the weaker its conjugate