Chem 30 Unit 3 Flashcards
Equilibrium
a state of a closed system in which all measurable properties are constant
Dynamic equilibrium
a balance between forward and reverse processes occurring at the same rate
Ice tables
Initial, Changes, Equilibrium
in an ice table…
Products always start at zero
Reactants go down; products go up
<50% reaction =
reactants favoured, reverse reaction, k <1
> 50% reaction =
products favoured, forward reaction, k>1
> 99% reaction =
quantitative, complete reaction, k is a very large number
if there is no reaction
k = 0
when is a reaction quantitative (arrow)?
single arrow
what to not include in K value calculations?
a solid in a gas reaction or water (l) in an aqueous solution reaction)
Le Chatelier’s Principle
disturbed close systems will shift to restore equilibrium
Le Chatelier’s Principle says…
Conditions affecting equilibrium are temperature, pressure, and concentration
3 stages of Le Chatelier’s
Initial equilibrium state, Shifting non-equilibrium state, New equilibrium state
in concentration shifts…
k value remains constant
in temperature shifts…
k value changes
in an endothermic reaction…
when temp increases, k value increases, vice versa
in an exothermic reaction…
when temp increases, k value decreases, vice versa
pressure/volume shifts
k value remains constant. (pressure/volume shifts are only for gases)
Pressure increase/volume decrease:
shift towards the side with fewer moles of molecules
Pressure decrease/volume increase:
shift towards the side with more moles of molecules
when there is equal moles on each side and a volume/pressure shift…
no change occurs / no shift
a catalyst…
Changes the rate of both forward and reverse reaction by the same amount, therefore it does not affect the position of the equilibrium.
If inert gases are added to increase the total pressure of the system…
nothing will change. The equilibrium pressure will not change.
pH/pOH sig digs
the numbers behind the decimal place are significant
strong acid
an acid that completely dissociates/ionizes (100%) into its ions
weak acid
an acid that slightly ionizes/dissociates into water
dilute solution
solution w/low ratio of solute to solvent
concentrated solution
a solution w/high ratio of solute to solvent
SO2 and CO2 react with water to form
H2SO3 and H2CO3
bronsted-lowry neutralization
results in a proton (hydrogen) transfer from the strongest acid to the strongest base.
in bronsted-lowry, a hydrogen =
a proton
conjugate acid base pairs
chemical species whose formulas differ only by one proton
amphiprotic
substances that can act as both a Bronsted Lowry acid and base.
if acid is above base…
it is products favoured
if acid is below base…
it is reactants favoured
polyprotic acids
acid species capable of donating more than one hydrogen during a reaction
monoprotic acids
possess only one hydrogen
polybasic species
base species capable of accepting more than one hydrogen during a reaction
monobasic
capable of accepting only one hydrogen
‘continuously added’ or ‘reacted until ___endpoints’
write more than one reaction (for polyprotic/basic)
endpoint
pH. the point where there is a colour change
equivalence point
volume. where endpoint occurs; measured quantity of titrant
buffer zone
period on titration curve before big change in pH
buffers
conjugate acid-base pair in a solution that resists sudden changes in pH when an acid or base is added
buffers must…
Has to be a weak conjugate acid-base pair (e.g. H2CO3 and HCO3-)
empirical
based on observations or experience
