Question 1

According to collision theory, which of the following is NOT a requirement for a successful chemical reaction between two molecules?

Accepted Answer

The molecules must collide with a catalyst present.

Question 2

Refer to the first image. Why does the first collision between NO and O3 not result in a reaction, while the third collision does?

Accepted Answer

The first collision has the wrong orientation, while the third has the correct orientation for bond formation.

Question 3

In the context of the second image, what is the main reason that the top collision does not result in a reaction?

Accepted Answer

The orientation of the molecules is incorrect for bond formation.

Question 4

Which of the following best describes the transition state in a chemical reaction, as shown in the third and fourth images?

Accepted Answer

A high-energy, short-lived configuration where old bonds are partially broken and new bonds are partially formed.

Question 5

Based on the energy diagrams shown (images 4 and 5), what does the activation energy $$E_a$$ represent?

Accepted Answer

The energy required to reach the transition state from the reactants.

Question 6

In a multi-step reaction (see image 6), what does the lowest point between two transition states represent?

Accepted Answer

An intermediate species.

Question 7

Refer to the kinetic energy distribution graphs (image 7). What happens to the fraction of molecules with enough energy to react as temperature increases?

Accepted Answer

It increases.

Question 8

Which of the following statements about the Arrhenius equation is correct?

Accepted Answer

A higher activation energy $$E_a$$ leads to a lower rate constant $$k at a $$given temperature.

Question 9

Given the linear form of the Arrhenius equation $$\$$\ln k = -\frac{E_a}{R} \frac{1}{T} + \ln A\$$\$$, what does the slope of a plot of $$\$$\ln k\$$\$$ versus $$\$$\frac{1}{T}\$$\$$ represent?

Accepted Answer

$$\$$-\frac{E_a}{R}\$$\$$

Question 10

A reaction has a rate constant $$k_1 = 0.010$$ \ \mathrm{s}^{-1}$$ at T_1$ = 300 \ \mathrm{K}$$ and $$k_2 = 0.040$$ \ \mathrm{s}^{-1}$$ at T_2$ = 320 \ \mathrm{K}. $$Using the two-point Arrhenius equation $$\$$\ln \frac{$$k_2$$}{$$k_1$$} = -\frac{E_a}{R} \left( \frac{1}{$$T_2$$} - \frac{1}{$$T_1$$} \right)\$$\$$, what is the activation energy $$E_a$$? (Use $$R = 8.314 \ \mathrm{J} / \mathrm{mol} \cdot \mathrm{K})$$

Accepted Answer

$$\E_a = 34.6$$ \ \mathrm{kJ} / \mathrm{mol}\$$\$$

Question 11

Which of the following changes will NOT increase the rate of a gas-phase reaction according to collision theory?

Accepted Answer

Decreasing the orientation factor.

Question 12

For the reaction $$\$$\mathrm{CO}(g) + \mathrm{O}_2(g) \rightarrow \mathrm{CO}_2(g) + \mathrm{O}(g)\$$\$$, why is the orientation of the collision important?

Accepted Answer

Only collisions where the C atom of CO contacts O2 can lead to reaction.

Question 13

A certain reaction has a high activation energy. What does this imply about the reaction rate at room temperature?

Accepted Answer

The reaction will proceed very slowly.

Question 14

If a catalyst is added to a reaction, which of the following statements is true?

Accepted Answer

The activation energy $$E_a$$ decreases.

Question 15

Which of the following best explains why increasing temperature increases the rate constant $$k$$ for a reaction?

Accepted Answer

It increases the number of collisions with sufficient energy to overcome the activation energy.

Question 16

In a reaction mechanism with two steps, which step determines the overall rate of the reaction?

Accepted Answer

The step with the highest activation energy.

Question 17

A reaction has a rate constant $$k = 0.0117 \ \mathrm{s}^{-1} at$$ $$400.0 \ \mathrm{K}$$ and an activation energy of $$122 \ \mathrm{kJ} / \mathrm{mol}. $$What is the expected rate constant at $$450.0 \ \mathrm{K}$$? (Use $$R = 8.314 \ \mathrm{J} / \mathrm{mol} \cdot \mathrm{K})$$

Accepted Answer

$$\k = 0.069$$ \ \mathrm{s}^{-1}\$$\$$

Question 18

Which of the following is a correct interpretation of the y-intercept in a plot of $$\$$\ln k\$$\$$ versus $$\$$\frac{1}{T}\$$\ ($$see image 8)?

Accepted Answer

It is equal to $$\$$\ln A\$$\$$, where $$A is $$the pre-exponential factor.

L21 Collision Theory, Activation Energy, and the Arrhenius Equation

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