ATAR Unit 3 (1) Flashcards
open system
exchanges energy & matter w. surroundings
closed system
exchanges only energy w. surroundings
reversible reaction
reaction where the products once formed can react together to re-form the reactants
reversibility [chemical]
only some chemical changes are reversible
reversibility [physical]
physical changes are usually reversible
four common reversible systems
evaporation & condensation of water [physical]
saturated sugar / salt solution [physical]
oxygen transport in blood [physical]
synthesis of ammonia [chemical]
static equilibrium
position of balance is achieved but no processes are happening [e.g. seesaw]
dynamic equilibrium
equal rate of forward & reverse reactions is achieved in closed systems
macroscopic properties remain constant & microscopic processes continue
reversibility [considering activation energy]
reactants collide w. sufficient energy [Eₐ] to form products
products collide w. sufficient energy [reverse Eₐ] to form reactants
extent of reaction
indicates how much product is formed at equilibrium
rate of reaction
measures the change in reactants & products w. time
graphing rate vs time
shape of the graph [rate theory]
graphing concentration vs time
stoichiometry of the reaction [coefficient]
le chatalier’s principle
if stress is applied to a system at equilibrium, the system will act to oppose the stress & restore equilibrium
increase temperature [exothermic reaction]
endothermic reaction absorbs heat
reverse reaction is favoured
moves to left-hand-side
reactants are favoured
K𝒸 decreases
decrease temperature [exothermic reaction]
exothermic reaction releases heat
forward reaction is favoured
moves to right-hand-side
products are favoured
K𝒸 increases
increase temperature [endothermic reaction]
endothermic reaction absorbs heat
forward reaction is favoured
moves to right-hand-side
products are favoured
K𝒸 increases
decrease temperature [endothermic reaction]
exothermic reaction releases heat
reverse reaction is favoured
moves to left-hand-side
reactants are favoured
K𝒸 decreases
increasing temperature effect [collision theory]
more kinetic energy within reactants & products
molecules move faster
more successful collisions
greater rate of reaction
pressure’s effect on K𝒸
changing pressure has no effect on the K𝒸 value
what if the number of molecules is equal on both sides of the chemical equation [2 : 2 molecules equation] ? [pressure]
change in pressure will not shift the position of equilibrium [no effect]
volume’s effect on pressure
if volume is doubled, pressure is halved
if volume is halved, pressure is doubled
increase pressure [3 : 2 molecules equation]
moves to the side of fewest molecules
net forward reaction
decrease pressure [3 : 2 molecules equation]
moves to the side of more molecules
net reverse reaction
increasing pressure effect [collision theory]
reduced volume equals increased pressure
molecules are closer together
increased frequency of collisions
greater rate of reaction
increase reactant
formation of more products
position of equilibrium shifts right
net forward reaction
increase product
formation of more reactants
position of equilibrium shifts left
net reverse reaction
decrease reactant
formation of more reactants
position of equilibrium shifts left
net reverse reaction
decrease product
formation of more products
position of equilibrium shifts right
net forward reaction
inert gas’ effect on K𝒸
adding an inert gas has no effect on the K𝒸 value
concentration’s effect on K𝒸
changing concentration has no effect on the K𝒸 value
increase dilution
moves to the side of more molecules
equilibrium is restored
catalyst’s effect on K𝒸
a catalyst has no effect on the K𝒸 value
homogenous system
reactants & products are in the same phase
heterogeneous system
reactants & products are in different phases
K𝒸 expression
products to the power of their coefficient[s] divided by reactants to the power of their coefficient[s]
what species do & do not appear in a K𝒸 expression ?
solids & liquids do not appear
aqueous & gases do appear
liquids do appear [if all species in the reaction are liquid]
liquids do appear [if H₂O is a reactant / product]
Q𝒸 > K𝒸
moves to left-hand-side
more reactants
Q𝒸 < K𝒸
moves to right-hand-side
more products