Summary EDEXCEL A LEVEL CHEMISTRY UNIT 11 EQUILIBRIUM II

11.1 REVERSIBLE REACTIONS & DYNAMIC
EQUILIBRIUM
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Dynamic equilibrium - Forwards and backwards reactions occur at constant rates and
so there is no overall change.



11.2 THE EQUILIBRIUM LAW
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● Homogeneous systems.
In hetrogeneous equilibrium, solids and pure liquids aren't expressed in the Kc
expression as their concentrations stay constant.

The equilibrium constant can also be calculated from experimental data.
A mixture will eventually lead to equilibrium.
● Samples can be titrated to find the equilibrium concentration.



11.3 GASEOUS EQUILIBRIA
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Partial pressure - Pressure that the gas would exert if it were the only gas present in
the container.
● The sum of individual partial pressures is the total pressure.

The moles of gas determines the pressure.
● Partial pressure is proportional to the concentration of gas in the mixture.
A mole fraction is the proportion of a particular gas in a gas mixture.
● Total pressure is shared between gases according to their mole fractions.