1.06 Chemical Equilibria Flashcards
Define the term dynamic equilibrium.
The forward and backward reaction rates are unchanging and so the concentration of all reactants and products are constant
Give an essential condition for an equilibrium mixture.
Equilibrium occurs in a closed system (where no reactants or products escape).
State Le Chatelier’s principle.
If a system at equilibrium is disturbed, the equilibrium moves in the direction to counteract the change.
In an equilibrium where the forward reaction enthalpy change is positive (dH=+), what effect would increasing the temperature have on the eq. position?
It would shift the equilibrium position to the right as the forward reaction is endothermic, so by increasing the temperature the endothermic reaction rate increases to counteract the change.
What would happen to the equilibrium position of 2A(g) + B(g) ⇌ 2C(g) + 2D(g) if the pressure was increased ?
It would shift to the right as the reaction that produces the fewer moles of gas is favoured as it counteracts the change.
Why may a high pressure be used to produce D in the reaction 2A(g) + B(g) ⇌ 2C(g) + 2D(g) in an industrial context ?
The high pressure increases the collision frequency of particles and therefore the rate of successful collisions (rate of reaction)
This is a compromise pressure between an economically viable rate of D production and a lower yield of D.
What effect does a catalyst have on equilibria position ?
No effect, as it lowers the Ea of the forward and reverse reactions equally.
What condition effects the value of Kc?
Only temperature.
Deduce an expression for Kc for the following reaction : 2[A] + 3[B] ⇌ [C] + [D] + 4[E].
Kc = [C][D][E]⁴ / [A]²[B]³.
Deduce the units for Kc : Kc = [C][D][E]⁴ / [A]²[B]³
Mol 1 dm-3.
What type of system is Kc relevant for ?
Homogeneous systems in equilibrium.
What does the value of Kc suggest ?
Greater than 1 suggests it is further right, less than 1 suggests it is further left.
What effect does decreasing the temperature in an endothermic forward reaction have on the value of Kc ?
Kc decreases.
What effect does increasing the temperature in an endothermic forward reaction have on the value of Kc ?
Kc increases.
What effect does decreasing the temperature in an exothermic forward reaction have on the value of Kc ?
Kc increases.
