Q: Given the reaction $$2O_3(g) \rightarrow 3O_2(g)$$, if $$\Delta[O_2$]/\Delta t = 6.0 \times 10$$^{-5}$$\ \text{M/s}$$, what is $$-\Delta[O_3$]/\Delta t at $$the same instant?

$$4.0 \times 10$$^{-5}$$\ \text{M/s}$$

Q: For the reaction $$aA + bB \rightarrow cC + dD$$, the general expression for the rate is:

$$\text{Rate} = -\frac{1}{a} \frac{d[A]}{dt} = -\frac{1}{b} \frac{d[B]}{dt} = \frac{1}{c} \frac{d[C]}{dt} = \frac{1}{d} \frac{d[D]}{dt}$$

Question 1

Which of the following best describes the difference between the average rate and the instantaneous rate of a chemical reaction?

Accepted Answer

The average rate is calculated over a finite time interval, while the instantaneous rate is the slope of the tangent to the curve at a specific instant.

Question 2

For the reaction $$2HI(g) ightarrow H_2$(g) + I_2$(g)$$, if the rate of disappearance of $$HI is$$ $$0.040\ 	ext{M/s}$$, what is the rate of appearance of $$I_2$$?

Accepted Answer

$$0.020\ 	ext{M/s}$$

Question 3

Given the reaction $$2O_3(g) ightarrow 3O_2(g)$$, if $$\Delta[O_2$]/\Delta t = 6.0 	imes 10$$^{-5}$$\ 	ext{M/s}$$, what is $$-\Delta[O_3$]/\Delta t at $$the same instant?

Accepted Answer

$$4.0 	imes 10$$^{-5}$$\ 	ext{M/s}$$

Question 4

Which statement about the rate law for a reaction is correct?

Accepted Answer

The rate law must be determined experimentally and the exponents may differ from the stoichiometric coefficients.

Question 5

For a reaction $$A ightarrow \,	ext{products}$$, the rate law is found to be $$	ext{Rate} = k[A]^2. If $$the concentration of $$A is $$doubled, how does the rate change?

Accepted Answer

The rate quadruples.

Question 6

A reaction has the rate law $$	ext{Rate} = k[A][B]^2. In a $$mixture with $$[A] = 3$$ and $$[B] = 7$$, what is the relative rate (in terms of $$k$$)?

Accepted Answer

$$k(3)(7)^2 = 147k$

Question 7

Which factor does NOT affect the rate of a chemical reaction?

Accepted Answer

Color of the reactants

Question 8

The Arrhenius equation relates the rate constant $$k to $$temperature $$T$$ and activation energy $$E_a. $$Which is the correct form of the Arrhenius equation?

Accepted Answer

$$k = Ae$$^{-E_a/RT}$$

Question 9

If a reaction is first order in $$A$$, which integrated rate law describes the change in $$[A]$$ over time?

Accepted Answer

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

Question 10

A reaction has a half-life that does NOT depend on the initial concentration of reactant. What is the order of this reaction?

Accepted Answer

First order

Question 11

Which experimental method is commonly used to determine the rate law of a reaction?

Accepted Answer

Method of Initial Rates

Question 12

For the reaction $$aA + bB \rightarrow cC + dD$$, the general expression for the rate is:

Accepted Answer

$$	ext{Rate} = -\frac{1}{a} \frac{d[A]}{dt} = -\frac{1}{b} \frac{d[B]}{dt} = \frac{1}{c} \frac{d[C]}{dt} = \frac{1}{d} \frac{d[D]}{dt}$$

Question 13

Which statement about a catalyst is TRUE?

Accepted Answer

A catalyst provides an alternative pathway with lower activation energy.

Question 14

In the reaction mechanism below, which step is the rate-determining step?
Step 1: $$NO_2 + CO$$ \rightarrow NO + $$CO_2 ($$slow)
Step 2: $$NO + O_2$ \rightarrow NO_2$ (fast)

Accepted Answer

Step 1

Question 15

Which of the following is a correct statement about reaction intermediates?

Accepted Answer

Intermediates are formed and consumed during the reaction mechanism.

Question 16

According to collision theory, which factor increases the rate of a reaction?

Accepted Answer

Increasing the concentration of reactants

Question 17

If the rate constant $$k$$ for a reaction increases with temperature, what does this imply about the activation energy $$E_a$$?

Accepted Answer

$$E_a is $$positive

Question 18

Which graphical method would you use to determine if a reaction is second order with respect to $$A$$?

Accepted Answer

Plot $$1/[A] vs. $$time and look for a straight line

Question 19

Enzymes are biological catalysts. Which statement best describes how enzymes work?

Accepted Answer

Enzymes provide a specific active site that binds substrates, lowering the activation energy.

Chemical Kinetics: Rates of Chemical Reactions

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