Question

Consider the following reaction at equilibrium. 2CO2 (g) 2CO (g) + O2 (g) H° = -514 kJ Le Châtelier's principle predicts that the equilibrium partial pressure of CO (g) can be maximized by carrying out the reaction ________. a. at high temperature and high pressure b. at high temperature and low pressure c. at low temperature and low pressure d. at low temperature and high pressure e. in the presence of solid carbon

Answer 1

Answer:

C. at low temperature and low pressure.

Explanation:

• Le Châtelier's principle states that when there is an dynamic equilibrium, and this equilibrium is disturbed by an external factor, the equilibrium will be shifted in the direction that can cancel the effect of the external factor to reattain the equilibrium.

• For the reaction:

2CO₂(g) ⇄ 2CO(g) + O₂(g), ΔH = -514 kJ.

Effect of pressure:

• When there is an increase in pressure, the equilibrium will shift towards the side with fewer moles of gas of the reaction. And when there is a decrease in pressure, the equilibrium will shift towards the side with more moles of gas of the reaction.

• The reactants side (left) has 2.0 moles of gases and the products side (right) has 3.0 moles of gases.

So, decreasing the pressure will shift the reaction to the side with higher no. of moles of gas (right side, products), so the equilibrium partial pressure of CO (g) can be maximized at low pressure.

Effect of temperature:

• The reaction is exothermic because the sign of ΔH is (negative).

• So, we can write the reaction as:

2CO₂(g) ⇄ 2CO(g) + O₂(g) + heat.

• Decreasing the temperature will decrease the concentration of the products side, so the reaction will be shifted to the right side to suppress the decrease in the temperature, so the equilibrium partial pressure of CO (g) can be maximized at low temperature.

• So, the right choice is:

C. at low temperature and low pressure.