10: Equilibrium I

Question 1

What is meant by dynamic equilibrium?

Answer 1

The rate of the forward reaction is equal to the rate of the backward reaction.
The concentrations of reactants and products remain constant.

Question 2

Predict and justify the qualitative effect of a change in temperature on a homogeneous system in equilibrium.

Answer 2

Increasing temperature promotes the endothermic reaction as it takes in the extra energy.

Decreasing the temperature promotes the exothermic reaction as it releases the energy that is removed.

Question 3

Predict the effect of a change in concentration on a homogeneous system in equilibrium.

Answer 3

Increasing the concentration of a reactant causes a shift to the right.

Increasing the concentration of a product causes a shift to the left.

Question 4

Predict the effect of a change in pressure on a homogeneous system in equilibrium.

Answer 4

Increasing the pressure of a gaseous reaction causes a shift towards the side with fewer molecules.
Decreasing the pressure of a gaseous reaction causes a shift towards the side with more molecules.

Question 5

Deduce an expression for Kc for the reaction:
2A + B ⇌ C + 3D

Answer 5

Kc = [C][D]³ / [A]²[B]