AS.9 Chemical Equillibrium Flashcards
Irreversible reactions
Enormous amount of energy required to reverse
Reversible reactions
Do not have such enormous enthalpy values
Properties of dynamic equilibrium
Rates of the forward and reverse are equal
Concentrations of reactants and products remain constant
Properties such as temperature and colour remain constant
Must occur in closed system
Le chateliers
A system at dynamic equilibrium will shift to oppose the effect of a change
What does a shift to the left cause
Products to reactants rate is decreased
Decreases yield of products
What does a shift to the right cause
Reactants to products rate is decreased
Increases yield of products
Le chateliers - changing concentration
If any concentration is increased, equilibrium will shift to opposite side to reduce increased concentration
Le chateliers - pressure
If increased, shift to side with fewer moles to reduce pressure
Le chateliers - temperature
Increasing temp, shifts in endothermic direction to absorb heat and lower temp
Compromise conditions
Conditions actually used are a compromise between high yield, rate of reaction, safety concerns and economic costs
Compromise - temperature
Too low - lower rate of reaction too much
Too high - expensive
Compromise - pressure
Too high - too dangerous and expensive
Too low - lowers rate of reaction too much
Kc
Equilibrium constant
[products] / [reactants]
Multiply if more than one product or reactant
To the power of coefficient
The magnitude of Kc
If greater than 1, position is to the right
If less than 1, position is to the left
