Chem 12 U1C1 - Equilibrium

open system

allows matter and energy to move in and out

closed system

only allows energy to move in and out

reversible reaction

reactions where the reactants can form products and the products can form reactants

all ______ changes are reversible, whereas only some ______ reactions are reversible

physical, chemical

the reversibility of chemical reactions is dependent on the _______ ______ of both the forward and reverse reactions

activation energies

for a reversible reaction, both the activation energies must be ___ enough that sufficient particles will have enough ______ for a successful collision

low, energy

dynamic equilibrium

when the amount of reactants and products remain constant even though forward and reverse reactions are still occurring

steady state

system has constant properties

conditions for dynamic equilibrium

closed system, reversible reaction

at equilibrium, the

rate of forward and reverse reactions are the same, concentrations and macroscopic properties remain constant

what type of equilibrium graph is this?

concentration vs time

what kind of equilibrium graph is this?

rate vs time

reaction quotient (Q)

same calculation as the equilibrium expression

if Q=K, then

the system is at equilibrium

if Q < K, then

there are less products and more reactants than at equilibrium

If Q > K, then

there are more products and less reactants than at equilibrium

a large value of K =

reaction goes towards completion

small value of K =

reaction occurs to a small extent

value of K close to 1 =

significant concentrations of both products and reactants at equilibrium

yield

how much product can be produced

rate

how quickly that yield is achieved

if the concentration of a reactant is increased,

then the rate of the forward reaction will increase

if the concentration of a product is increased,

then the rate of reverse reaction will increase

if the volume of a system is halved, the pressure, and therefore concentration of all gases would double,

both rates of reaction increase, but the side with more moles will increase more

more volume =

favour side with more moles

less volume =

favour side with less moles

increase in temp increases both, but

increases rate of endothermic more

decrease in temp decreases both, but

decreases endothermic more to favour exothermic

addition of a catalyst

does not affect equilibrium, but increases how quickly it is reached

le chateliers principle states that

if a system at equilibrium is disturbed, the system will act to partially negate the change

activation energy

the energy needed to break the reactants bond in order to form new products

chemical change

a change that produces new substances

chemical system

the chemicals involved in a reaction

collision theory

for a reaction to proceed, the reactant particles must collide with sufficient energy and an appropriate orientation

endothermic reaction

absorbs energy from the surroundings, products have more energy than reactants

enthalpy

the total energy of a substance

equilibrium constant (K)

the value of the ratio between the concentration of products to reactants

equilibrium expression

the ratio of the concentration of products to reactants used to calculate the equilibrium constant

exothermic reaction

releases heat energy to the surroundings, products have less energy than reactants

forward reaction

process of reactants forming products

partial pressure

the pressure exerted by a single gas in a gas mixture

physical change

a change where no new substances are formed