Consider the reversible gas-phase synthesis of methanol represented by the thermochemical … — JAMB UTME

Consider the reversible gas-phase synthesis of methanol represented by the thermochemical equation below:

CO(g) + 2H_2(g) \rightleftharpoons CH_3OH(g) \quad \Delta H < 0

Match each applied stress condition on the left with its correct effect on the system at equilibrium on the right.

Increasing total pressure by decreasing container volumeShifts equilibrium position to the right, increasing $CH_3OH(g)$ yield
Increasing the temperature of the reaction systemShifts equilibrium position to the left, decreasing $CH_3OH(g)$ yield
Adding a solid ZnO/Cr₂O₃ catalyst to the reaction vesselIncreases the rate of attainment of equilibrium without shifting its position
Adding helium gas at constant volumeHas no effect on partial pressures or the equilibrium position

Answer

Increasing total pressure shifts the equilibrium to the right; increasing temperature shifts the equilibrium to the left; adding a catalyst accelerates the rate of reaching equilibrium without shifting its position; adding an inert gas at constant volume has no effect on the equilibrium position.

Each stress causes an equilibrium adjustment governed strictly by Le Chatelier's principle. Pressure increases shift the position toward the side with fewer gas moles (the product side). Temperature increases favor the endothermic direction (the reverse reaction). Catalysts accelerate reaction rates equally in both directions without altering the equilibrium position, and inert gas additions at constant volume do not modify the partial pressures of the reacting components.

Step-by-Step Solution

Analyze the effect of volume reduction (pressure increase)

Reactants contain

1 + 2 = 3

gaseous moles, while products contain

1

gaseous mole. Increasing pressure shifts equilibrium towards fewer gaseous moles (to the right).

Le Chatelier's principle states that an increase in pressure shifts equilibrium toward the side with fewer moles of gas.

Analyze the effect of temperature increase

The forward reaction is exothermic (

\Delta H < 0

). Increasing temperature causes an equilibrium shift in the endothermic direction (to the left).

According to Le Chatelier's principle, adding thermal energy shifts equilibrium to favor heat absorption.

Analyze the effect of catalyst addition

A catalyst decreases activation energy for both directions equally.

Catalysts increase reaction rate and reduce equilibrium attainment time, but do not alter relative thermodynamic stabilities or equilibrium positions.

Analyze the effect of inert gas addition at constant volume

Concentrations and partial pressures of reacting gases remain constant.

Since total volume is fixed, molar concentrations of reacting species do not change, leaving equilibrium undisturbed.

Key Concept

Le Chatelier's Principle on Equilibrium Position and Rate of Reaction

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic