Methanol (CH3 OH) is manufactured by the reaction of carbon...

Methanol $\left(\mathrm{CH}_{3} \mathrm{OH}\right)$ is manufactured by the reaction of carbon monoxide with hydrogen in the presence of a $\mathrm{Cu} / \mathrm{ZnO} / \mathrm{Al}_{2} \mathrm{O}_{3}$ catalyst: $$\mathrm{CO}(g)+2 \mathrm{H}_{2}(g) \frac{\mathrm{Cu} / \mathrm{ZnO} / \mathrm{Al}_{2} \mathrm{O}_{3}}{\text { catalyst }} \mathrm{CH}_{3} \mathrm{OH}(g) \quad \Delta H^{\circ}=-91 \mathrm{kJ}$$ Does the amount of methanol increase, decrease, or remain the same when an equilibrium mixture of reactants and products is subjected to the following changes? (a) The temperature is increased (b) The volume is decreased (c) Helium is added (d) CO is added (e) The catalyst is removed

Methanol $\left(\mathrm{CH}_{3} \mathrm{OH}\right)$ is manufactured by the reaction of carbon monoxide with hydrogen in the presence of a $\mathrm{Cu} / \mathrm{ZnO} / \mathrm{Al}_{2} \mathrm{O}_{3}$ catalyst:

$$\mathrm{CO}(g)+2 \mathrm{H}_{2}(g) \frac{\mathrm{Cu} / \mathrm{ZnO} / \mathrm{Al}_{2} \mathrm{O}_{3}}{\text { catalyst }} \mathrm{CH}_{3} \mathrm{OH}(g) \quad \Delta H^{\circ}=-91 \mathrm{kJ}$$

Does the amount of methanol increase, decrease, or remain the same when an equilibrium mixture of reactants and products is subjected to the following changes?
(a) The temperature is increased
(b) The volume is decreased
(c) Helium is added
(d) CO is added
(e) The catalyst is removed

Key Concepts

Chemical Equilibrium

Chemical equilibrium refers to the state in a reversible chemical reaction where the rates of the forward and reverse reactions have become equal, resulting in constant concentrations of reactants and products over time. At equilibrium, although individual molecules continue to react, there is no net change in the overall concentrations of species present.

Le Chatelier's Principle

Le Chatelier's principle is a key concept that predicts how an equilibrium system responds to disturbances such as changes in concentration, pressure, and temperature. When a system at equilibrium experiences a stress, it will shift in the direction that tends to counteract that stress, thereby re-establishing equilibrium.

Effect of Temperature on Equilibrium

The influence of temperature on equilibrium is particularly important in exothermic and endothermic reactions. For exothermic reactions, an increase in temperature effectively adds heat to the system, causing the equilibrium to shift towards the reactants in order to absorb the excess heat, while a decrease in temperature favors the exothermic product formation.

Effect of Pressure and Volume on Equilibrium

Changes in pressure and volume can influence gas-phase equilibria by altering the total number of moles of gas present. According to Le Chatelier's principle, decreasing the volume (increasing pressure) shifts the equilibrium toward the side with fewer moles of gas, while increasing volume (reducing pressure) shifts it toward the side with more moles.

Role of Inert Gases in Equilibrium

The addition of inert gases can affect a reaction's equilibrium depending on how the inert gas is added. When an inert gas is added at constant volume, it does not change the partial pressures of the reacting gases and thus does not shift the equilibrium. In contrast, if added at constant pressure, it effectively increases the volume, potentially altering the equilibrium conditions in gas-phase reactions.

Role of Catalysts in Equilibrium

Catalysts accelerate the rate at which equilibrium is reached by providing an alternative reaction pathway with a lower activation energy. However, they do not change the position of the equilibrium or the final concentrations of reactants and products; they simply help the system reach equilibrium faster.

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