Question 1

Which of the following best describes the role of activation energy ($$E_a) in a $$chemical reaction, as illustrated in a potential energy diagram?

Accepted Answer

It is the minimum energy required for reactants to form the activated complex and proceed to products.

Question 2

According to the Arrhenius equation $$k = Ae$$^{-E_a/RT}$$, what happens to the rate constant k$ if the activation energy E_a$ increases while temperature T$ remains constant?

Accepted Answer

The rate constant $$k$$ decreases.

Question 3

Which of the following statements about the frequency factor $$A in $$the Arrhenius equation is correct?

Accepted Answer

It is related to the frequency of collisions with proper orientation between reactant molecules.

Question 4

A reaction has a rate constant $$k_1 = 2.14$$ 	imes $$10^{-4}$$ \ \mathrm{M}^{-1}\mathrm{s}^{-1}$$ at 39.0$$\ ^\circ\mathrm{C}$$ and k_2$ = 1.64 	imes 10$$^{-3}$$ \ \mathrm{M}^{-1}\mathrm{s}^{-1} at$$ $$61.0\ ^\circ\mathrm{C}. If$$ $$R = 8.314 \ \mathrm{J}/\mathrm{mol}\cdot\mathrm{K}$$, what is the activation energy $$E_a in$$ $$\mathrm{kJ}/\mathrm{mol}$$? (Use $$T_1 = 312.15$$\ \mathrm{K}$$ and T_2$ = 334.15\ \mathrm{K})$$

Accepted Answer

$$E_a = 80.4\ \mathrm{kJ}/\mathrm{mol}$$

Question 5

Which of the following best explains why increasing temperature increases the rate of a chemical reaction?

Accepted Answer

It increases the fraction of molecules with kinetic energy greater than $$E_a.$$

Question 6

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

Accepted Answer

The negative activation energy divided by the gas constant, $$-E_a/R$$

Question 7

Which of the following is true for an exothermic reaction as shown in a potential energy diagram?

Accepted Answer

The energy of the products is lower than the energy of the reactants.

Question 8

A student is analyzing the effect of temperature on the rate constant $$k$$ for a reaction. If the student plots $$\ln k$$ versus $$1/T$$ and obtains a straight line with a slope of $$-9668.5$$, what is the activation energy $$E_a in$$ $$\mathrm{kJ}/\mathrm{mol}$$? ($$R = 8.314\ \mathrm{J}/\mathrm{mol}\cdot\mathrm{K})$$

Accepted Answer

$$E_a = 80.4\ \mathrm{kJ}/\mathrm{mol}$$

Question 9

Which of the following changes would result in a larger exponential factor $$e^{-E_a/RT} in $$the Arrhenius equation?

Accepted Answer

Decreasing the activation energy $$E_a or $$increasing the temperature $$T.$$

Question 10

A reaction has $$k_1 = 7.90$$ 	imes $$10^{-2}$$\ \mathrm{M}^{-1}\mathrm{s}^{-1}$$ at 508$$\ ^\circ\mathrm{C}$$ and k_2$ = 2.40 	imes 10$$^{-1}$$\ \mathrm{M}^{-1}\mathrm{s}^{-1} at$$ $$540\ ^\circ\mathrm{C}. $$What is the activation energy $$E_a in$$ $$\mathrm{kJ}/\mathrm{mol}$$? ($$T_1 = 781.15$$\ \mathrm{K}$$, T_2$ = 813.15\ \mathrm{K}$$, $$R = 8.314\ \mathrm{J}/\mathrm{mol}\cdot\mathrm{K})$$

Accepted Answer

$$E_a = 183\ \mathrm{kJ}/\mathrm{mol}$$

Question 11

Which of the following best describes the activated complex in a chemical reaction?

Accepted Answer

A chemical species with partially broken and partially formed bonds at the peak of the energy profile.

Question 12

In a thermal energy distribution diagram, what does the area under the curve to the right of the activation energy $$E_a$$ represent?

Accepted Answer

The fraction of molecules with enough energy to react.

Question 13

If a reaction has a high activation energy, what can be inferred about its rate at room temperature?

Accepted Answer

The reaction will proceed very slowly.

Question 14

Which of the following is a correct application of the two-point form of the Arrhenius equation?

Accepted Answer

Calculating the activation energy $$E_a if $$the rate constant values at two temperatures are known.

Question 15

Which of the following is NOT a requirement for a successful molecular collision leading to a chemical reaction?

Accepted Answer

Molecules must collide with a frequency factor greater than 1.

Chapter 15 lecture 3

스터디 가이드 - 연습 문제

학습 가이드 - 플래시카드