5.1 Qualitative understanding of equilibrium Flashcards
Le Chatelier's principle, minimising disturbances, collision theory
a reaction “goes to completion” when:
one reactant is used up completely
static equilibrium
(1) reaction goes to completion
(2) zero velocity (no net movement of P and R)
dynamic equilibrium
(1) reaction does not go to completion
(2) constant velocity (P and R still participating in reaction)
conditions for dynamic equilibrium
- A reversible reaction
- A closed system
- Macroscopic properties stay the same
- Concentrations of substances are constant
formation reaction slowing to equilibrium
concentration of reactants decrease > successful collisions decrease > rate of products produced decreases eventually to equilibrium
dissolution reaction slowing to equilibrium
- products reverse into reactants BUT:
(less reactants available) > reverse reaction slows to equilibrium
non-equilibrium systems
- Products are no longer in the system e.g. an open system.
- Products do not react with each other due to their highly stable nature.
- Forward reaction has a negative enthalpy change and positive entropy change.
2 examples of non-equilibrium systems
combustion and photosynthesis
4 stresses/factors
(1) concentration
(2) partial pressure (gas),
(3) total gas pressure (change in volume) or
(4) temperature
in terms of collision theory, the number of successful collision between the reactants to produce products, and between products to produce reactants are…
equal at equilibrium
effect of a catalyst on equilibrium
decreases time to reach equilibrium
increasing concentration of a reactant shifts the equilibrium…
right to make more products
Le Chatelier’s principle
a system responds to counteract a disruption to the system by establishing a new equilibrium
collision theory for increasing concentration of reactants
increased concentration = increased frequency of collisions = increased forward rate, then equilibrium
effect of dilution on equilibrium
decreased concentration = system favours the side with more moles
increasing pressure is the same as:
increasing concentration
relationship between pressure and volume
inversely proportional (Boyle’s law)
increased P = decreased V = shift to…
side with LESS gas moles
decreased P = increased V = shift to…
side with MORE gas moles
increasing T = shift to…
endothermic side (to absorb the T)
decreasing T = shift to…
exothermic side (to produce more T)
the only 2 stresses that affect can rate of reaction
temperature and catalysts
scientific way to say “all molecules/atoms/ions in an equation”
all chemical species involved
scientific way to say “where the equilibrium shifts to”
“the position of equilibrium”
if 1 mol of reactant shifts 2 moles up on a graph, then 1 mol of product will…
shift 2 moles down
cobalt chloride equilibrium equation and colours
hydrated cobalt solution + chloride ⇌ cobalt chloride + water
Co(H2O)6 +2(aq) + 4Cl-(aq) ⇌ CoCl4 -2(aq) + 6H2O(l)
hydrated cobalt is pink
cobalt chloride is blue
formation of cobalt chloride is exo or endo?
endothermic
nitrogen dioxide equilibrium equation and colours
dinitrogen tetroxide ⇌ nitrogen dioxide
N2O4(g) ⇌ 2 NO2(g)
LHS colourless
RHS brown
formation of nitrogen dioxide is exo or endo?
endothermic