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15-2: Equilibrium constant Expression

Initially only the forward reaction occurs, but once some product is formed,

the reverse reaction starts to occur

Amount of reactants and products remains constant throughout time

Why do we apply equilibrium constants with activities?

oWhen gases do not obey ideal laws, equilibrium constants may vary

with pressure or temperature, but activities get rid of this

Numerator is product of activities

Denominator is reactants on left side

15-3: relationships involving equilibrium constants

relationship of K to the balanced chemical equation

When we reverse an equation, we invert the value of K

When we multiply the coefficients in a balanced equation by a common

factor, we raise the equilibrium constant to the corresponding power

When we divide the coeffcients in a balanced equation by a common factor,

we take the corresponding root of the equilibrium constant

Equilibrium vapour pressures are just values of kP

15-4: Magnitude of Equilibrium Constant

large value of K signifies forward reaction (goes to completion)

small value of K means the reaction does not occur to a significant extent

15-5: Predicting direction of net change

predicting direction of net change in establishing equilibroium is important because

1. at times we do not need detailed equilibrium calculations, but only a

qualitative description of the changes that occur n establishing equilibrium

fromma given set of initial conditions

2. in some calculations, it is helpful to determine direction of net change as a

first step

reaction quotient (Q): any set of initial activities in a reaction mixture as a ratio

Q=K means reaction is at equilibrium

Qc<kc net change occurs from left to right (direction of forward reaction)

QC>KC net change occurs from right to left (direction of reverse reaction)

15-6: Le Chateliers Principle

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