1.6 Equilibria
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Define the term dynamic equilibrium
The rate of the forward reaction = the rate of the back reaction
Give an essential condition for an equilibrium mixture
Equilibrium occurs within a closed system OR Macroscopic properties do not change overtime
State Le Chatelier’s principle
If a system at equilibrium is disturbed, the equilibrium moves in the direction that tends to reduce the disturbance
CH4 + H2O ⇌ CO + 3H2 ^H = +210 kJ/mol What effect would increasing the temperature have on the position of equilibrium
The equilibrium position would shift to the right
In the equation : CH4 + H2O ⇌ CO + 3H2 ^H = +210 kJ/mol What effect would increasing the pressure have on the position of equilibrium
The position of equilibrium would shift to the left
In the equation : CH4 + H2O ⇌ CO + 3H2 ^H = +210 kJ/mol Suggest and explain why an industrial chemist may use a high pressure for the production of hydrogen from the above reaction
• The high pressure increases the collision frequency thus increasing the rate of reaction • This is a compromise pressure between an economically viable rate of reaction and a slightly lower yield of hydrogen
What effect does a catalyst have on the position of equilibrium
No Effect
Which condition affects the value of Kc : Temperature Concentration Catalyst Pressure
Temperature
For the reaction below, deduce the an expression for Kc 2[A] + 3[B] + [C] ⇌ [D] + 4[E]
Kc = [D][E]4 ——————— [A]2 x [B]3 x [C]
Deduce the units for Kc = [D][E]4 —————— [A]2[B]3[C]
Mol-1 dm3
What type of system is Kc relevant for
Homogenous systems in equilibrium
What does Kc being greater or lesser than 1 represent in terms of position of equilibrium
Kc > 1 = over to the right (more products) Kc < 1 = over to the left (more reactants)
What effect does decreasing the temperature in an endothermic reaction have on Kc
Kc decreases
What effect does increasing the temperature in an exothermic reaction have on Kc
Kc decreases
What effect does increasing the temperature in an endothermic reaction have on Kc
Kc increases
What effect does decreasing the temperature in an exothermic reaction have on Kc
Kc increases