Equilibrium

Question 1

Law of Mass Action

Answer 1

• General Rxn: aA + bB -> cC + dD.
• K(eq) = ([C]ᶜ[D]ᵈ)/([A]ᵃ[B]ᵇ) = Pr/Re.
• K(eq) = k/k₋₁.
• At equilibrium, the rate of the forward reaction equals the rate of the reverse reaction, entropy is at a maximum, and Gibbs free energy is at a minimum, linking the concepts of thermodynamics and kinetics.
• Equilibrium Expressions have exponents that are equal to stoichiometric coefficients, whereas Rate Laws have exponents that must be experimentally determined.

Question 2

Reaction Quotient

Answer 2

• Q < K(eq): ΔG < 0, reaction proceeds in forward direction.
• Q = K(eq): ΔG = 0, reaction is in dynamic equilibrium.
• Q > K(eq): ΔG > 0, reaction proceeds in reverse direction.

• K(eq) with large negative exponent implies that reactants are strongly favored at equilibrium. Therefore, the amount that has reacted can be considered negligible.

Question 3

Kinetic Control vs Thermodynamic Control

Answer 3

• Kinetic products are formed at lower temperatures (with small heat transfer) and are considered less stable (higher-energy) products.
• Thermodynamic products are formed at higher temperatures (with large heat transfer) and are considered more stable (lower-energy) products.