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Zorluk: KolayLe Chatelier's Principle
For the endothermic steam-reforming process represented by the thermochemical equation below:
CH4(g)+H2O(g)⇌CO(g)+3H2(g)ΔH=+206 kJ mol−1CH_4(g) + H_2O(g) \rightleftharpoons CO(g) + 3H_2(g) \quad \Delta H = +206\text{ kJ mol}^{-1}
Match each applied change (stress) on the system with its corresponding effect on the equilibrium position or system performance.
  • Increasing the reaction temperatureShifts equilibrium to the right, favoring product formation
  • Increasing the total pressure on the containerShifts equilibrium to the left, favoring reactant formation
  • Adding a nickel catalyst to the systemIncreases reaction rates without changing the equilibrium position
  • Continuous removal of CO(g)CO(g) from the mixtureShifts equilibrium to the right to replenish the removed product

Cevap

Increasing temperature shifts the equilibrium to the right; increasing pressure shifts the equilibrium to the left; adding a nickel catalyst increases reaction rates without changing the equilibrium position; continuous removal of carbon monoxide shifts the equilibrium to the right.
According to Le Chatelier's principle: heating an endothermic reaction shifts equilibrium toward products; increasing total pressure shifts equilibrium toward the side with fewer gas molecules (reactants, 2 moles vs 4 moles); adding a catalyst speeds up reaching equilibrium without shifting its position; and removing a product shifts equilibrium toward products to compensate for the decrease in concentration.

Adım Adım Çözüm

1
Analyze the temperature change using enthalpy sign
The positive enthalpy change (ΔH=+206 kJ mol−1\Delta H = +206\text{ kJ mol}^{-1}) indicates an endothermic forward reaction. Raising the temperature shifts the equilibrium to the right.
Le Chatelier's principle dictates that adding thermal energy favors the heat-absorbing (endothermic) direction.
2
Count gaseous moles on both sides to determine the pressure effect
Reactant gas moles = 2 (CH4+H2OCH_4 + H_2O), Product gas moles = 4 (CO+3H2CO + 3H_2). Increasing pressure shifts the system to the left.
An increase in pressure shifts the equilibrium position toward the side with fewer moles of gas to reduce pressure.
3
Determine the role of a catalyst
The nickel catalyst accelerates both forward and backward reaction rates equally.
Catalysts do not alter the position of dynamic equilibrium or change product yield.
4
Determine the concentration change effect
Removing CO(g)CO(g) causes a rightward shift in equilibrium.
Removing a component drives the system to shift in the direction that replaces it.

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Le Chatelier's Principle
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Le Chatelier's Principle

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