Kinetics: The Pre-Equilibrium Approximation

The video tutorial explains the pre-equilibrium approximation, a technique used in chemical kinetics. It discusses the assumptions involved, such as the establishment of equilibrium between reactants before product formation. The tutorial derives the equilibrium expression and explains how to calculate the rate of reaction and concentration of intermediates. It compares the pre-equilibrium approximation with the steady state approximation, highlighting differences in assumptions and applications. The video emphasizes the importance of understanding both techniques, especially the steady state approximation, which is widely used in enzyme kinetics and other mechanisms.

What is the key assumption of the pre-equilibrium approximation?

• C is consumed before forming an equilibrium with A and B.

• A and B are consumed at the same rate as C.

• A and B form an equilibrium with C before C is converted to D.

• D is formed before any equilibrium is established.

How is the equilibrium constant expressed in terms of rate constants?

• As the sum of the forward and reverse rate constants.

• As the product of the forward and reverse rate constants.

• As the ratio of the forward rate constant to the reverse rate constant.

• As the difference between the forward and reverse rate constants.

What is the expression for the concentration of intermediate C?

• K-1 / K1 * A * B

• K1 * K2 / (A * B)

• K1 / K-1 * A * B

• K2 / K1 * A * B

How is the rate of formation of product D expressed in the pre-equilibrium approximation?

• K2 * A * B / K1

• K2 * K1 / K-1 * A * B

• K1 * K2 / K-1 * C

• K-1 * K2 / K1 * D

What is a key difference in the denominator of the rate expressions between the pre-equilibrium and steady state approximations?

• Neither includes K2 in the denominator.

• Both include K2 in the denominator.

• Steady state includes K2, while pre-equilibrium does not.

• Pre-equilibrium includes K2, while steady state does not.

Which approximation is more widely used in enzyme kinetics?

• Neither is used

• Steady state approximation

• Pre-equilibrium approximation

• Both are equally used

In which mechanism is the steady state approximation used?

• Neither Michaelis-Menten nor Lindemann

• Both Michaelis-Menten and Lindemann

• Lindemann mechanism

• Michaelis-Menten equation