equilibrium Flashcards
le chatliers principle
when an external stress (change in concentration,pressure or temperature) is applied to a system in dynamic chemical equilibrium, the equilibrium (point) will change in such a way as to counteract the stress
dynamic chemical equilibrium
reversible rxn in which fwd + rvs reactions are taking place at the same rate, and hence the concentrations of reactants and products are constant
closed system
one in which mass is conserved inside the system but energy can enter or leave the system freely
open system
one in which both energy and matter can be exchanged between the system and its surroundings
decrease in temp
favours exothermic rxn to replace removed energy PRODUCE
^H<0
down-exit- negative- make out
increase in temp
favours endothermic to USE UP added energy
^H>0 positive
energy is reactant
decrease in volume
increase in pressure
both rxns experience increase in rate, rxn that produces fewer moles favoured
kc>1
eqm lies closer to products- RIGHT
graphs cross
[products] big
[reactants] small
graphs cross
kc<1
eqm lies closer to reactants (LEFT)
[products] small
[reactants] big
graphs never intersect
le chatliers answering
Disturbance (separate from result)
Oppose
Favoured Reaction (higher rate- fwd or rvs)
Eqm shift (fwd- left, rvs-right)
Result (observations)
concentration effects
direct- adding or removing product or reactant
indirect - involving substance nit in mixture (common ion effect, precipitation rxn)
concentration of reactant increased
d: increase in [ reactant ]
o: according to LCP, the system will favour the reaction that uses up reactant
f: therefore fwd rxn favoured
e: eqm shifts right to restore eqm
r: result specific to rxn , mention that reactants decrease therefore products increase
common ion effect w increase in product concentration
d: increase in [reactant] using common uon effect
o: according to LCP, system will favour rxn that uses up product
f: therefore rvs rxn favoured
e: eqm shift left to restore eqm
r: result, state that product decrease and reactant increase
precipitation rxn where [product] decrease
d: decrease in [product] due to precipitation
o: according to LCP, system favour rxn that increases [product]
f: fwd
e: right
r: specific to rxn
pressure
inversely proportional to volume
change in volume will affect concentration of all gases
both fwd + rvs rxn
LCP decrease in volume
d: decrease in volume causes increase in pressure, both fwd+ rvs rates increase
o: according to LCP system favour rxn that produces fewer moles of gas (look at mole ratio )
f: rxn favoured
e: eqm shifts
r: specific to q
LCP increase in volume
d: increase in volume causes decrease in pressure, both fwd+ rvs rates decrease
o: according to LCP system favour rxn that produces more moles of gas (look at mole ratio )
f: rxn favoured
e: eqm shifts
r: specific to q
decrease in temperature favoured?
exothermic
decrease - exit- exo
decrease in temp
d: decrease in temp
o: bith fwd + rvs rates decrease, LCP - system favor rxn that increases temp (produces energy) and therefore favour exothermic rxn
rest is rxn dependent
increase in temp favour?
endothermic
IN crease ENdo
increase in temp
d: increase in temp
o: bith fwd + rvs rates increase due to increase in Ek, LCP - system favor rxn that decreases temp (uses endothermic and therefore favour exothermic rxn
rest is rxn dependent
energy product
energy released
heat of reaction negative
fwd rxn - exothermic
rvs rxn - endothermic
energy reactant
energy used up
heat of reaction positive
fwd- endothermic
rvs: exothermic
catalyst
always increases
equal effect on fwd + rvs reactions
eqm position unchanged
[reactants] and [products] remains same
Kc
only for aq + g
mole coefficients become exponents
unaffected by change in pressure or concentration
affected by change in temperature (favour rvs to decrease, favour fwd- increase)
find kc
use moles to get concentration
sub into expression
kc not at eqm- reaction quotient Q compare Kc to Q
Ka
acid
large- strong acid ionises almost completely
small- weak acid, partial ionisation
Kb
base
large- strong base dissociates completely
small- weak base
Ksp
solubility product
production of ions
if possible- soluble
if negative- insoluble
