1. Consider the following equilibrium system: C(s) + CO2(g) 2CO(g) ∆Hr° = +120 kJ
Indicate the shift in equilibrium, if any, for each of the following scenarios: a) Adding CO2(g) b) Adding C c) Lowering the temperature d) Increasing pressure e) Adding a catalyst

a) equilibrium shifts towards the right

b) equilibrium shifts towards the right

c) equilibrium shifts towards the left

d) has no effect on equilibrium position

e) has no effect on equilibrium position

Explanation:

A reversible reaction may attain equilibrium in a closed system. A chemical system is said to be in a state of dynamic equilibrium when the rate of forward reaction is equal to the rate of reaction.

According to Le Chateliers principle, when a constraint such as a change in temperature, pressure, volume or concentration is imposed upon a system in equilibrium, the equilibrium position shifts in such a way as to annul the constraint.

When the concentration of reactants is increased, the equilibrium position is shifted towards the right hand side and more products are formed. For an endothermic reaction, the reverse reaction is favoured by a decrease in temperature. Increase in pressure has no effect on the system since there are equal volumes on both sides of the reaction equation. Similarly, the addition of a catalyst has no effect on the equilibrium position since it speeds up both the forward and reverse reactions to the same extent.