key term - Pressure change

Definition

Pressure change refers to the variation in the pressure of a system, which can influence the position of equilibrium in a chemical reaction. When the pressure of a system is altered, particularly in reactions involving gases, the system will respond by shifting the equilibrium position to counteract that change. This response is outlined by a principle that predicts how systems at equilibrium behave when external conditions are modified.

5 Must Know Facts For Your Next Test

1. In a gaseous reaction, increasing the pressure favors the side with fewer moles of gas, while decreasing the pressure favors the side with more moles.
2. Pressure changes affect only reactions where gases are involved; changes in liquid or solid phases do not have an impact on equilibrium position.
3. Using a closed system allows pressure changes to affect chemical equilibrium since no gas can escape or enter the system.
4. The relationship between volume and pressure change follows Boyle's Law, where decreasing volume increases pressure and vice versa.
5. The response to pressure change can be quantitatively analyzed using the ideal gas law, $$PV = nRT$$, which relates pressure (P), volume (V), and temperature (T) for a fixed amount of gas.

Review Questions

• How does increasing pressure influence the direction of equilibrium in a gaseous chemical reaction?
  • Increasing pressure in a gaseous chemical reaction causes the equilibrium to shift towards the side of the reaction that has fewer moles of gas. This occurs because the system attempts to reduce pressure by favoring the formation of products or reactants that occupy less volume. Understanding this concept helps predict how reactions respond to changes in external conditions.
• Evaluate how Le Chatelier's Principle applies to changes in pressure and what implications this has for industrial chemical processes.
  • Le Chatelier's Principle indicates that increasing pressure in a closed system will shift equilibrium toward the side with fewer gas moles. In industrial applications, this principle is utilized to optimize yield in reactions such as ammonia synthesis, where higher pressures favor product formation. By carefully controlling pressure conditions, industries can enhance efficiency and maximize output.
• Synthesize information on how both temperature and pressure changes can simultaneously affect equilibrium, using specific examples to illustrate your points.
  • Both temperature and pressure changes can significantly influence equilibrium position. For instance, in an exothermic reaction like the synthesis of ammonia ($$N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g) + heat$$), increasing temperature shifts equilibrium to favor reactants. Conversely, increasing pressure shifts it toward products due to fewer gas moles on that side. Analyzing how these factors interact helps chemists design more effective chemical processes by adjusting conditions strategically for desired outcomes.

Related terms

Equilibrium constant: A numerical value that expresses the ratio of products to reactants at equilibrium for a given reaction at a specific temperature.

Le Chatelier's Principle:

A principle stating that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change.

Partial pressure: The pressure exerted by a single gas in a mixture of gases, which contributes to the total pressure of the system.