Gas-phase equilibrium

Definition

Gas-phase equilibrium refers to the state in which the rates of the forward and reverse reactions of a gas-phase chemical reaction are equal, leading to constant concentrations of reactants and products over time. This concept is crucial for understanding how temperature and pressure changes can influence the position of equilibrium in gas-phase reactions, affecting the yield of products.

5 Must Know Facts For Your Next Test

1. At gas-phase equilibrium, the concentration of reactants and products remains constant, but not necessarily equal.
2. Increasing the temperature of an exothermic reaction shifts the equilibrium position toward the reactants, while for endothermic reactions, it shifts toward the products.
3. Changes in pressure will affect gas-phase equilibria involving gases; increasing pressure favors the side with fewer moles of gas.
4. The value of the equilibrium constant (K) changes with temperature but remains constant with changes in concentration or pressure.
5. The concept of gas-phase equilibrium is essential in applications such as chemical reactors and environmental chemistry, where gas-phase reactions are prevalent.

Review Questions

• How does Le Chatelier's Principle apply to gas-phase equilibrium when temperature is altered?
  • Le Chatelier's Principle states that a system at equilibrium will adjust to counteract any changes made to it. When the temperature of a gas-phase reaction is increased, for an exothermic reaction, this shift will favor the formation of reactants, while an endothermic reaction will favor product formation. Understanding this principle helps predict how equilibrium positions shift due to thermal changes.
• Discuss how pressure changes affect gas-phase equilibria and give an example.
  • Changes in pressure significantly influence gas-phase equilibria by favoring the side of the reaction with fewer moles of gas. For example, consider the reaction 2 NO(g) ⇌ N2(g) + O2(g). If we increase the pressure, the equilibrium will shift to the right toward N2 and O2 since there are fewer moles of gas on that side (1 mole) compared to the left side (2 moles). This principle is key in processes such as ammonia synthesis.
• Evaluate how understanding gas-phase equilibrium can impact industrial chemical processes.
  • Understanding gas-phase equilibrium is crucial for optimizing industrial chemical processes like Haber process for ammonia synthesis or catalytic converters in vehicles. By manipulating factors such as temperature and pressure, industries can maximize product yield and efficiency. For instance, knowing how to shift equilibrium positions effectively allows chemists and engineers to design processes that meet production goals while minimizing costs and resource use, making this knowledge vital for sustainable practices.

Related terms

Le Chatelier's Principle:

A principle stating that if an external change is applied to a system at equilibrium, the system will adjust itself to counteract that change and re-establish equilibrium.

Equilibrium Constant (K): A numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium for a given reaction at a specific temperature.

Reaction Quotient (Q): A ratio that compares the current concentrations of products and reactants in a reaction to predict the direction in which the reaction will proceed to reach equilibrium.