Chapter 7: Equilibria Flashcards
(18 cards)
Define dynamic equilibrium.
A dynamic equilibrium occurs when the forward and reverse reactions happen at the same rate in a closed system, and concentrations of reactants and products remain constant.
What are the characteristics of a system at equilibrium?
- Rate of forward reaction = rate of reverse reaction
- Concentrations of all species are constant
- Occurs in a closed system
State Le Chatelier’s Principle.
If an external change is made to a system at equilibrium, the system shifts to oppose the change.
What is the effect of increasing reactants on the position of equilibrium?
Increasing reactants shifts equilibrium right.
What is the effect of increasing products on the position of equilibrium?
Increasing products shifts equilibrium left.
How does increasing pressure affect the position of equilibrium in gases?
Increasing pressure favors the side with fewer moles of gas.
What is the effect of increasing temperature on an endothermic reaction?
Increasing temperature favors the endothermic reaction.
What is the effect of decreasing temperature on an exothermic reaction?
Decreasing temperature favors the exothermic reaction.
Do catalysts affect the position of equilibrium?
No effect on position; speeds up both forward and reverse reactions equally.
Write the expression for the equilibrium constant Kc.
For a reaction: aA + bB ⇌ cC + dD, Kc = [C]^c [D]^d / [A]^a [B]^b
How do you calculate Kc from concentrations of equilibrium species?
Substitute concentrations into the Kc expression.
What affects the units of Kc?
Units vary depending on the reaction.
How are the units for Kc deduced?
Based on the expression’s powers of mol dm⁻³. Simplify accordingly.
How is Kc affected by changes in conditions?
- Kc is constant at a fixed temperature
- Only temperature affects Kc
What happens to Kc when the temperature increases for an exothermic reaction?
Increasing temperature decreases Kc.
What happens to Kc when the temperature increases for an endothermic reaction?
Increasing temperature increases Kc.
What does a large Kc (>1) indicate about the extent of reaction?
Equilibrium lies to the right (more products).
What does a small Kc (<1) indicate about the extent of reaction?
Equilibrium lies to the left (more reactants).
