Question 1

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

Accepted Answer

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

Question 2

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

Accepted Answer

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

Question 3

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 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 $$\Delta S = +120\ \mathrm{J/(mol\cdot K)}. At$$ $$T = 298\ \mathrm{K}$$, is the reaction spontaneous?

Accepted Answer

Yes, because $$\Delta G is $$negative.

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 identified as:

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 product 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 molecules contains a chiral carbon?

Accepted Answer

2-butanol

Question 15

A sample contains 70% of one enantiomer and 30% of the other. What is the enantiomeric excess (e.e.)?

Accepted Answer

$$40\%$$

Question 16

Which of the following compounds is meso?

Accepted Answer

Tartaric acid (2,3-dihydroxybutanedioic acid) with two chiral centers and a plane of symmetry

Question 17

Which of the following statements about chirality is correct?

Accepted Answer

A molecule can be chiral even if it does not contain a chiral carbon.

Question 18

Which of the following best describes the difference between atom economy and theoretical yield?

Accepted Answer

Atom economy measures the efficiency of a reaction in terms of how many atoms from the reactants are incorporated into the desired product, while theoretical yield is the maximum amount of product that can be formed from given reactants.

Question 19

Which of the following is the correct formula to calculate the optical rotation ($$[\alpha]) of a $$solution, given observed rotation $$\alpha_{obs}$$, path length $$l (in dm$$), and concentration $$c (in g/mL$$)?

Accepted Answer

$$[\alpha] = \frac{\alpha_{obs}}{l 	imes c}$$

Organic Chemistry Exam Review: Thermodynamics, Kinetics, and Stereochemistry

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