Question 1

Which of the following equations correctly relates the Gibbs free energy change ($$\Delta G) to $$enthalpy ($$\Delta H$$), entropy ($$\Delta S$$), and temperature ($$T$$)?

Accepted Answer

$$\Delta G = \Delta H - T\Delta S$$

Question 2

Which of the following best describes the relationship between the equilibrium constant ($$K_{eq}) $$and the standard Gibbs free energy change ($$\Delta G^\circ$$)?

Accepted Answer

$$\Delta G^\circ = -RT \ln K_{eq}$$

Question 3

A reaction has $$\Delta H = -50\ \mathrm{kJ/mol}$$ and $$\Delta S = -100\ \mathrm{J/(mol\cdot K)}. At $$what temperature will this reaction change from spontaneous to non-spontaneous?

Accepted Answer

$$T = 500\ \mathrm{K}$$

Question 4

Given $$\Delta G^\circ = -8.314\ \mathrm{J/(mol\cdot K)} 	imes 298\ \mathrm{K} 	imes \ln K_{eq}$$, what is the value of $$K_{eq} if$$ $$\Delta G^\circ = -5.7\ \mathrm{kJ/mol} at$$ $$298\ \mathrm{K}$$?

Accepted Answer

$$K_{eq} \approx 100$$

Question 5

Which of the following statements about entropy ($$\Delta S) is $$correct?

Accepted Answer

Entropy is a measure of the disorder or randomness of a system.

Question 6

A reaction has $$\Delta H = +40\ \mathrm{kJ/mol}$$ and $$\Delta S = +120\ \mathrm{J/(mol\cdot K)}. $$Which of the following best describes the reaction?

Accepted Answer

Endothermic and more favorable at high temperatures

Question 7

Given the following experimental data for a reaction: Doubling $$[A]$$ doubles the rate, doubling $$[B]$$ quadruples the rate. What is the correct rate law?

Accepted Answer

$$	ext{rate} = k[A][B]^2$$

Question 8

Which of the following best describes the conceptual meaning of the Arrhenius equation?

Accepted Answer

It relates the rate constant to temperature and activation energy.

Question 9

In a reaction coordinate diagram, the rate-limiting step is:

Accepted Answer

The step with the highest energy transition state

Question 10

Which of the following statements about bond dissociation energies is correct?

Accepted Answer

Bond breaking is endothermic and requires energy input.

Question 11

Given the following bond dissociation energies: $$\mathrm{C-H} = 410\ \mathrm{kJ/mol}$$, $$\mathrm{C-C} = 350\ \mathrm{kJ/mol}$$, $$\mathrm{C-F} = 485\ \mathrm{kJ/mol}$$, $$\mathrm{C-Br} = 280\ \mathrm{kJ/mol}$$, which bond is the weakest?

Accepted Answer

$$\mathrm{C-Br}$$

Question 12

According to the Hammond Postulate, why is bromination more selective than chlorination in the halogenation of alkanes?

Accepted Answer

The transition state for bromination resembles the products more closely, making it more selective.

Question 13

Which of the following terms describes molecules that are non-superimposable mirror images of each other?

Accepted Answer

Enantiomers

Question 14

Which of the following is true about a carbon atom that is chiral (asymmetric)?

Accepted Answer

It is bonded to four different groups.

Question 15

Given a sample containing 70% of one enantiomer and 30% of its mirror image, what is the enantiomeric excess (e.e.)?

Accepted Answer

40%

Question 16

Which of the following statements about meso compounds is correct?

Accepted Answer

Meso compounds are achiral despite having chiral centers.

Question 17

Which of the following best describes a compound that is chiral but does not contain a chiral (asymmetric) carbon?

Accepted Answer

It has a chiral axis or plane, such as in certain allenes or biphenyls.

Question 18

Which of the following best distinguishes atom economy from theoretical yield?

Accepted Answer

Atom economy measures the efficiency of a reaction in incorporating all atoms into the desired product, while theoretical yield is the maximum amount of product possible.

Question 19

A solution of a chiral compound has a specific rotation of $$+25^\circ. If $$the observed rotation for a sample is $$+10^\circ$$, what is the percent composition of the major enantiomer in the sample?

Accepted Answer

70%

Question 20

Which of the following is NOT a type of isomerism?

Accepted Answer

Isotopic isomerism

Organic Chemistry Test 2 Study Guide: Thermodynamics, Kinetics, and Stereochemistry

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