3.2.3 - Chemical Equilibrium Flashcards
What is chemical equilibrium?
Chemical equilibrium is the state in a reversible reaction where the rates of the forward and reverse reactions are equal, and the concentrations of reactants and products remain constant over time.
What is the difference between a dynamic equilibrium and a static equilibrium?
Dynamic equilibrium occurs in reversible reactions where the rates of the forward and reverse reactions are equal. Static equilibrium refers to a situation where no movement occurs, typically in non-reversible processes.
What does Le Chatelier’s Principle state?
Le Chatelier’s Principle states that if a system at equilibrium is subjected to a change in conditions, the system will adjust to counteract the change and restore equilibrium.
What factors can affect the position of equilibrium?
The position of equilibrium can be affected by changes in concentration, temperature, and pressure (for gaseous reactions).
How does concentration affect equilibrium?
If the concentration of a reactant or product is changed, the equilibrium will shift to counteract the change. If a reactant concentration increases, the equilibrium shifts to produce more products, and vice versa.
How does temperature affect equilibrium?
If the temperature is increased, the equilibrium shifts in the direction of the endothermic reaction (absorbs heat). If the temperature is decreased, the equilibrium shifts in the direction of the exothermic reaction (releases heat).
How does pressure affect equilibrium in gaseous reactions?
If the pressure is increased, the equilibrium will shift toward the side with fewer moles of gas. If the pressure is decreased, the equilibrium shifts toward the side with more moles of gas.
What is the equilibrium constant (Kc)?
The equilibrium constant (Kc) is a numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium, each raised to the power of their stoichiometric coefficients.
What is the general expression for the equilibrium constant (Kc)?
For a general reaction:
aA + bB ⇌ cC + dD, the equilibrium constant expression is:
Kc = [C]^c [D]^d / [A]^a [B]^b
(where square brackets represent concentration).
What does a large value of Kc indicate about the position of equilibrium?
A large value of Kc (greater than 1) indicates that the equilibrium lies toward the products side, meaning there are more products than reactants at equilibrium.
What does a small value of Kc indicate about the position of equilibrium?
A small value of Kc (less than 1) indicates that the equilibrium lies toward the reactants side, meaning there are more reactants than products at equilibrium.
How does the catalyst affect equilibrium?
A catalyst speeds up both the forward and reverse reactions equally, allowing the system to reach equilibrium faster. However, it does not affect the position of equilibrium.
What is the relationship between Kc and temperature?
Kc is temperature-dependent. For an endothermic reaction, an increase in temperature increases Kc, while for an exothermic reaction, an increase in temperature decreases Kc.
How does a change in volume affect equilibrium?
Changing the volume of a gaseous system affects the pressure. Decreasing the volume increases the pressure, causing the equilibrium to shift towards the side with fewer moles of gas.
What is the reaction quotient (Q)?
The reaction quotient (Q) is calculated using the same formula as the equilibrium constant (Kc), but with the concentrations of reactants and products at any point in time, not just at equilibrium. Comparing Q with Kc helps predict the direction of the reaction.
What happens if Q < Kc?
If Q < Kc, the reaction will shift to the right (toward the products) to reach equilibrium.
What happens if Q > Kc?
If Q > Kc, the reaction will shift to the left (toward the reactants) to reach equilibrium.
What is the contact process?
The contact process is the industrial process used to make sulfuric acid. It involves the reaction of sulfur dioxide (SO₂) and oxygen (O₂) to form sulfur trioxide (SO₃). The equilibrium of this reaction is affected by pressure and temperature.
What is the Haber process?
The Haber process is the industrial process for synthesizing ammonia (NH₃) from nitrogen (N₂) and hydrogen (H₂). The equilibrium is influenced by temperature and pressure to maximize ammonia production.
What are homogeneous equilibria?
Homogeneous equilibria are equilibria where all the reactants and products are in the same phase (e.g., all gases, or all solutions).
What are heterogeneous equilibria?
Heterogeneous equilibria are equilibria where reactants and products are in different phases (e.g., a solid in equilibrium with a gas or liquid).
Why are solids and liquids omitted from the equilibrium constant expression?
Solids and liquids have constant concentrations in a given reaction, so they do not affect the equilibrium position and are therefore omitted from the Kc expression.
What does it mean if Kc = 1?
If Kc = 1, the concentrations of products and reactants at equilibrium are approximately equal, indicating that the reaction is balanced and neither side is favored.
What is Kp?
Kp is the equilibrium constant for reactions involving gases, expressed in terms of partial pressures rather than concentrations.
How is Kp related to Kc?
The relationship between Kp and Kc is given by the equation:
Kp = Kc(RT)^(Δn),
where R is the gas constant, T is temperature in Kelvin, and Δn is the change in the number of moles of gas between products and reactants.
