Question 1

Which of the following best describes the difference between thermodynamics and kinetics in chemical reactions?

Accepted Answer

Thermodynamics determines if a reaction will occur, while kinetics determines how fast it will occur.

Question 2

Which law of thermodynamics states that the entropy of a system approaches a constant value as the temperature approaches absolute zero?

Accepted Answer

3rd law

Question 3

Consider the reaction: $$2 \mathrm{H}_2(g) + \mathrm{O}_2(g) \rightarrow 2 \mathrm{H}_2\mathrm{O}(l). $$The value of $$\Delta G^0$ is very negative, but the reaction does not occur spontaneously at room temperature. Why?

Accepted Answer

The reaction is kinetically inhibited due to a high activation energy barrier.

Question 4

Which of the following statements about catalysts is correct?

Accepted Answer

Catalysts provide an alternative pathway with lower activation energy.

Question 5

Given the Gibbs-Helmholtz equation $$\Delta G = \Delta H - T \Delta S$$, which condition will always result in a spontaneous process?

Accepted Answer

$$\Delta H  0$$

Question 6

A diamond is thermodynamically unstable compared to graphite, yet diamonds do not spontaneously turn into graphite at room temperature. This is an example of:

Accepted Answer

A reaction with a negative $$\Delta G$$ but high activation energy (kinetic inhibition).

Question 7

Which of the following best describes entropy ($$S$$)?

Accepted Answer

A measure of the order or randomness in a system.

Question 8

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

Accepted Answer

$$E_a is $$the minimum energy required for reactants to form products.

Question 9

Which of the following is a consequence of the 2nd law of thermodynamics?

Accepted Answer

The entropy of the universe tends to increase in any spontaneous process.

Question 10

A reaction has $$\Delta H = -100 kJ/$$mol and $$\Delta S = -200 J/($$mol·K). At what temperature (in K) does the reaction change from spontaneous to non-spontaneous?

Accepted Answer

$$T = 500 K$$

Question 11

Which of the following is true for a process at equilibrium?

Accepted Answer

$$\Delta G = 0$$

Question 12

In the reaction $$\mathrm{NO} + \mathrm{Cl}_2 \rightarrow \mathrm{NOCl} + \mathrm{Cl}$$, what is the effect of a catalyst?

Accepted Answer

It lowers the activation energy required for the reaction.

Question 13

Which of the following best explains why a mixture of hydrogen and oxygen gases can remain unreacted for centuries at room temperature?

Accepted Answer

The activation energy barrier is too high for the reaction to proceed.

Question 14

Which of the following is NOT a correct statement about the laws of thermodynamics?

Accepted Answer

The 2nd law states that entropy decreases in all natural processes.

Question 15

Which of the following reactions is an example of a catalyzed reaction in the atmosphere?

Accepted Answer

$$\mathrm{O}_3 + \mathrm{O} \rightarrow 2 \mathrm{O}_2$$ with chlorine atoms as catalysts

Question 16

Which of the following is true about the effect of temperature on the spontaneity of a reaction, according to the Gibbs-Helmholtz equation?

Accepted Answer

Increasing temperature increases the influence of entropy ($$\Delta S) on$$ $$\Delta G.$$

Question 17

Which of the following best describes a metastable compound?

Accepted Answer

A compound that is thermodynamically unstable but kinetically stable.

Question 18

Which of the following is a correct interpretation of the reaction coordinate diagram for an exothermic reaction?

Accepted Answer

The activation energy is the energy difference between reactants and the transition state.

Question 19

Which of the following is a real-life example of kinetic inhibition?

Accepted Answer

A mixture of hydrogen and oxygen gases that does not react until a spark is introduced.

Thermodynamics and Kinetics in Chemical Reactions: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards