Q: For the reaction $$4NH_3(g) + 5O_2(g) \rightarrow 4NO(g) + 6H_2O(g)$$, if the rate of formation of NO is $$2.0 \times 10$$^{-4}$$ mol/L·s, what is the rate of consumption of O_2$?

$$2.5 \times 10$$^{-4}$$ mol/L·s$

Question 1

Which of the following best describes the instantaneous rate of a chemical reaction?

Accepted Answer

It is the rate measured at a specific moment, typically at time zero, using the slope of the tangent to the concentration vs. time curve.

Question 2

For the reaction $$4NH_3(g) + 5O_2(g) ightarrow 4NO(g) + 6H_2O(g)$$, if the rate of formation of NO is $$2.0 	imes 10$$^{-4}$$ mol/L·s, what is the rate of consumption of O_2$?

Accepted Answer

$$2.5 	imes 10$$^{-4}$$ mol/L·s$

Question 3

Which factor does NOT generally increase the rate of a chemical reaction?

Accepted Answer

Decreasing the surface area of a solid reactant

Question 4

Given the rate law $$	ext{rate} = k[A]^2[B]$$, what is the overall order of the reaction?

Accepted Answer

Third order

Question 5

A reaction is found to be first order in $$NO_2$$ and zero order in $$CO at$$ $$100^\circC. $$What is the correct rate law for this reaction?

Accepted Answer

$$	ext{rate} = k[NO_2$]$$

Question 6

For a first-order reaction, which of the following integrated rate laws is correct?

Accepted Answer

$$\ln[A]_t = -kt + \ln[A]_0$$

Question 7

The half-life of a first-order reaction is given by which equation?

Accepted Answer

$$t_{1/2} = \frac{0.693}{k}$$

Question 8

A sample of $$^{14}C$$ has a half-life of 5730 years. What is the rate constant $$k$$ for its radioactive decay?

Accepted Answer

$$k = \frac{0.693}{5730}$$ years$$^{-1}$$

Question 9

If the initial concentration of a reactant in a first-order reaction is 0.100 M, how much remains after two half-lives?

Accepted Answer

0.025 M

Question 10

Which statement about the activation energy ($$E_a) of a $$reaction is correct?

Accepted Answer

It is the minimum energy required for a reaction to occur.

Question 11

According to the Arrhenius equation $$k = Ae$$^{-E_a/RT}$$, what happens to the rate constant k$ as temperature increases?

Accepted Answer

It increases exponentially.

Question 12

Which of the following is true about a catalyst in a chemical reaction?

Accepted Answer

It provides an alternative reaction pathway with lower activation energy.

Question 13

In a proposed mechanism for the reaction $$2NO_2Cl \rightarrow 2NO_2 + Cl_2$, the first step is NO_2Cl$$ \rightarrow $$NO_2 + Cl$ (slow), followed by NO_2Cl + Cl$$ \rightarrow $$NO_2$$ + $$Cl_2 ($$fast). What is the overall rate law?

Accepted Answer

$$	ext{rate} = k[NO_2Cl]$$

Question 14

Which of the following best describes a reaction intermediate?

Accepted Answer

A substance that is produced in one step and consumed in a subsequent step.

Question 15

For a second-order reaction with respect to $$A$$, which integrated rate law is correct?

Accepted Answer

$$\frac{1}{[A]_t} = kt + \frac{1}{[A]_0}$$

Question 16

Which of the following is a termolecular elementary reaction?

Accepted Answer

$$2NO(g) + O_2$(g) \rightarrow 2NO_2(g)$$

Question 17

Which of the following statements about the rate-determining step in a reaction mechanism is correct?

Accepted Answer

It determines the overall rate law for the reaction.

Question 18

A student doubles the concentration of $$NO in $$the reaction $$2NO(g) + 2H_2(g) \rightarrow N_2$(g) + 2H_2O(g)$$ and observes that the rate quadruples, while doubling $$H_2$$ doubles the rate. What is the correct rate law?

Accepted Answer

$$	ext{rate} = k[NO]^2[H_2$]$$

Chapter 12: Chemical Kinetics – Study Notes

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