Equilibrium (6)

Question 1

Reaction quotient (Q)

Answer 1

At any point in time during a rxn, we can measure the concentrations of all of the reactants and products and calculate the reaction quotient

Q = [C]^c [D] ^d / [A] ^a [B] ^b

Question 2

Reaction quotient (Q) and Equilibrium constant (Keq)

Answer 2

Q = at any time Keq = at equilibrium

Q < Keq , ΔG (-) , forward rxn
Q > Keq, ΔG (+) , reverse rxn
Q = Keq, ΔG (0), at equilibrium

no solid or liquid in calculations

Question 3

Equilibrium calculation (Keq)

Answer 3

Keq = products / reactants

• If Keq > 1, the product is greater conc at equilibrium
• Keq almost 1, both product and reactant present at equilibrium
• Keq < 1, reactant is greater conc at equilibrium
• Keq «< 1, the amount of reactants that been converted to products can be negligible in comparison to the initial reactant.

x is neglibile if Keq is very negative: (1-x)

Question 4

Changes in Concentration (La Chatelier’s principle)

Answer 4

Reactant added or product removed Qc < Keq. (SHIFT RIGHT)

Reactant removed or product added Qc < Keq (SHIFT LEFT)

Question 5

Changes in Pressure (La Chatelier’s principle)

Answer 5

The system will move forward or in reverse, always toward whichever side has the lower total number of moles of gas.

When pressure increases, the system will react with fewer moles of gas.

When the pressure decreases, the system will react with more moles of gas.

Question 6

Changes in Temperature (La Chatelier’s principle)

Answer 6

If the reaction is exothermic, ΔH < 0, Heat functions as a product

If the reaction is endothermic, ΔH > 0, Heat functions as a reactant.

Question 7

Kinetic product and Thermodynamic product

Answer 7

At lower temperature, Kinetic product is favored

At higher temperature, the thermodynamic product is favored

Kinetic products form faster than thermodynamic

Thermodynamic product has lower free energy, which means greater stability.