a. Describe three characteristic features of chemical equilibrium.

b. When 1mol of N₂O₄ gas is allowed to come to equilibrium with NO₂ gas under standard conditions, only 20% of the N₂O₄ is converted to NO₂.

N₂O₄ 2NO₂ ΔH_r = +58 kJ mol^–1

i. Give the equilibrium expression for this reaction. 

ii. Calculate the value of Kc for the reaction. Assume that the volume of the reaction mixture is 1 dm³.

c. Explain the effect on Kc of an increase in:

i. Pressure

ii. Temperature.