Q: A nonenzymatic elementary reaction $$A + B \rightarrow C$$ has $$[A] = 20\ \mathrm{mM}$$ and produces $$5\ \mathrm{mM} of$$ $$C$$ per minute. What is the rate constant $$k$$?

$$2.5 \times 10$$^{-3}$$\ \mathrm{min}^{-1}$$

Q: The hypothetical elementary reaction $$2A + B \rightarrow C$$ has a rate constant of $$10^7$$\ \mathrm{M}^{-2}\mathrm{s}^{-1}$$. What is the reaction velocity when $$[A] = 1.0\ \mathrm{mM}$$?

$$1 \times 10^4$\ \mathrm{M}\mathrm{s}^{-1}$$

Question 1

Which statement best describes the reaction order for an elementary reaction?

Accepted Answer

It is always determined from the balanced chemical equation using substrate coefficients.

Question 2

For the non-elementary reaction: $$\mathrm{NO}_2 + \mathrm{CO} \rightarrow \mathrm{NO} + \mathrm{CO}_2$$, which of the following is true about its rate law?

Accepted Answer

The rate law must be experimentally determined and cannot be deduced from the overall balanced equation.

Question 3

Which of the following is the correct rate law for the elementary reaction $$2\mathrm{O}_3 \rightarrow 3\mathrm{O}_2$$?

Accepted Answer

$$v = k[\mathrm{O}_3]^2$$

Question 4

A zero order reaction has a rate law of $$v = k. $$What happens to the reaction rate if the substrate concentration is doubled?

Accepted Answer

The reaction rate remains unchanged.

Question 5

For a first order reaction, which of the following is true about the units of the rate constant $$k$$?

Accepted Answer

$$\mathrm{min}^{-1}$$

Question 6

Consider the reaction $$v = k[A][B]. If$$ $$[A] = 0.10\ \mathrm{M}$$ and $$[B] = 0.20\ \mathrm{M}$$, and $$k = 5.0\ \mathrm{M}^{-1}\mathrm{min}^{-1}$$, what is the reaction rate?

Accepted Answer

Question 7

Which of the following graphs best represents the rate of a zero order reaction as substrate concentration increases?

Accepted Answer

A horizontal line indicating constant rate regardless of substrate concentration.

Question 8

A second order reaction has the rate law $$v = k[A]^2. If$$ $$k = 2.0\ \mathrm{M}^{-1}\mathrm{min}^{-1}$$ and $$[A] = 0.5\ \mathrm{M}$$, what is the rate?

Accepted Answer

$$v = 0.5\ \mathrm{M}^{-1}\mathrm{min}^{-1}$$

Question 9

Which of the following is a pseudo first order reaction?

Accepted Answer

A reaction where one reactant is present in large excess, making its concentration effectively constant.

Question 10

For the reaction $$2A + B \rightarrow C$$, the rate law is $$v = k[A]^2[B]. $$What is the overall reaction order?

Accepted Answer

3

Question 11

A nonenzymatic elementary reaction $$A + B \rightarrow C$$ has $$[A] = 20\ \mathrm{mM}$$ and produces $$5\ \mathrm{mM} of$$ $$C$$ per minute. What is the rate constant $$k$$?

Accepted Answer

$$2.5 	imes 10$$^{-3}$$\ \mathrm{min}^{-1}$$

Question 12

The hypothetical elementary reaction $$2A + B \rightarrow C$$ has a rate constant of $$10^7$$\ \mathrm{M}^{-2}\mathrm{s}^{-1}$$. What is the reaction velocity when $$[A] = 1.0\ \mathrm{mM}$$?

Accepted Answer

$$1 	imes 10^4$\ \mathrm{M}\mathrm{s}^{-1}$$

Question 13

Which of the following is true for a first order reaction?

Accepted Answer

The rate is directly proportional to the concentration of a single substrate.

Question 14

In a second order reaction involving two different substrates, what are the units of the rate constant $$k$$?

Accepted Answer

$$\mathrm{M}^{-1}\mathrm{s}^{-1}$$

Question 15

Which scenario best describes a pseudo first order reaction in a biological system?

Accepted Answer

Enzyme-catalyzed hydrolysis of a substrate in the presence of excess water.

Question 16

For the reaction $$v = k[A][B]$$, if $$[A] is $$held constant and $$[B] is $$varied, what is the apparent reaction order with respect to $$B$$?

Accepted Answer

First order

Question 17

Which of the following is NOT a characteristic of zero order reactions?

Accepted Answer

The rate increases as substrate concentration increases.

Question 18

A reaction has the rate law $$v = k[A][B]. If$$ $$k = 1.0\ \mathrm{M}^{-1}\mathrm{s}^{-1}$$, $$[A] = 0.1\ \mathrm{M}$$, and $$[B] = 0.2\ \mathrm{M}$$, what is the rate?

Accepted Answer

$$0.02\ \mathrm{M}\mathrm{s}^{-1}$$

Question 19

Which of the following best explains why the rate law for a non-elementary reaction cannot be deduced from the overall balanced equation?

Accepted Answer

Because the reaction may proceed through multiple steps, each with its own rate law.

Reaction Orders and Kinetics in Biochemistry

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