Skip to main content

My Courses

AI Tools Channels Home

6. Thermodynamics and Kinetics

Entropy

6. Thermodynamics and Kinetics

Entropy

Guided videos.

Learn with Johnny

Go to the course

Explaining what entropy is.

Explaining what entropy is.

Johnny Betancourt

3 ways to increase entropy.

3 ways to increase entropy.

Johnny Betancourt

Practice this topic

Textbook Question

For each reaction, estimate whether ΔS° for the reaction is positive, negative, or impossible to predict. a. N-decane

heat catalyst —> Propene

(catalytic cracking)

Textbook Question

When ethene is mixed with hydrogen in the presence of a platinum catalyst, hydrogen adds across the double bond to form ethane. At room temperature, the reaction goes to completion. Predict the signs of ΔH° and ΔS° for this reaction. Explain these signs in terms of bonding and freedom of motion. ethene + H2 (Pt catalyst) ⇌ ethane

Textbook Question

For each reaction, estimate whether ΔS° for the reaction is positive, negative, or impossible to predict. b. The formation of diacetone alcohol: + OH- ⇌

Textbook Question

For each reaction, estimate whether ΔS° for the reaction is positive, negative, or impossible to predict. c. CH3COOH = CH3OH + H+ ⇌ CH3COOCH3 + H2O

Textbook Question

a. For which reaction in each set will ∆S° be more significant? b. For which reaction will ∆S° be positive? 1. A <--> B or A + B <--> C 2. A <--> B + C or A + B <--> C + D

Textbook Question

a. Which of the following reactions has the larger ∆S° value? b. Is the ∆S° value positive or negative? a. b.

Textbook Question

At what temperature does the entropy change of a process not contribute to the favorability of a process?

Textbook Question

(••••) The hydrogenation of alkenes is a reaction we study in Chapter 9. (b) Is this reaction favored or disfavored in terms of entropy?

Textbook Question

Through the course of this chapter, we have discussed only alkane chlorination and bromination, yet there are two other halogens we have not discussed. (b) Is radical iodination a favorable reaction? Do you expect it to be selective? Show your calculations.

Textbook Question

The dehydrogenation of butane to trans-but-2-ene has ΔH° = +116 kJ/mol (+27.6 kcal/mol) and ΔS° = +117J/kelvin-mol (+28.0 cal/kelvin-mol). a. Compute the value of ΔG° for dehydrogenation at room temperature (25 °C or 298 °K). Is dehydrogenation favored or disfavored? HINT: When you are doing synthesis problems, avoid using these high-temperature industrial methods. They require specialized equipment, and they produce variable mixtures of products.

Textbook Question

The dehydrogenation of butane to trans-but-2-ene has ΔH° = +116 kJ/mol (+27.6 kcal/mol) and ΔS° = +117J/kelvin-mol (+28.0 cal/kelvin-mol). a. Compute the value of ΔG° for dehydrogenation at room temperature (25 °C or 298 °K). Is dehydrogenation favored or disfavored? HINT: When you are doing synthesis problems, avoid using these high-temperature industrial methods. They require specialized equipment, and they produce variable mixtures of products.

Textbook Question

Estimate the value of entropy ( ∆S > 0 or ∆S<0 ) for the elimination step shown.

Textbook Question

Would you expect ∆S to be greater than, less than, or equal to zero in the following reactions? b.

Textbook Question

For each of the following processes, indicate whether you expect ∆S° to be greater than, less than, or equal to 0. Explain your answer.

(d) <IMAGE>

Textbook Question

For each of the following processes, indicate whether you expect ∆S° to be greater than, less than, or equal to 0. Explain your answer.

(c) <IMAGE>

Textbook Question

For each of the following processes, indicate whether you expect ∆S° to be greater than, less than, or equal to 0. Explain your answer.

(b) 2 C₆H₁₄(l) + 19 O₂9(g) → 12 CO₂(g) + 14 H₂O (g)

Textbook Question

Using the bond-dissociation energies in Table 5.6 (see Section 5.3.1), estimate the equilibrium constant of the following reaction at 298 K.

<IMAGE>

Textbook Question

For the following reactions we have not seen yet, which side, if either, would be favored by increasing the temperature?

(b) <IMAGE> ⇌ <IMAGE>

Textbook Question

Predict which side of the equilibrium is favored by ∆H, ∆G, and ∆S

<IMAGE>

Textbook Question

For each of the following processes, indicate whether you expect ∆S° to be greater than, less than, or equal to 0. Explain your answer.

(a) Boiling water

Textbook Question

(••••) In Chapter 13, we discuss the ring-opening reactions of epoxides, such as the one shown here. <IMAGE>

(b) Predict the sign of ∆S°.

Textbook Question

Would you expect ∆S to be greater than, less than, or equal to zero in the following reactions?

a.

Textbook Question

For a reaction carried out at 25 °C with an equilibrium constant of 1 * 10-3, to increase the equilibrium constant by a factor of 10:

a. how much must ∆G° change?

b. how much must ∆H° change if ∆S° = 0 kcal mol -1K-1?

c. how much must ∆S° change if ∆H° = 0 kcal mol -1?

Textbook Question

From the following rate constants, determined at five temperatures, calculate the experimental energy of activation and ∆G‡, ∆H‡, and ∆S‡ for the reaction at 30 °C:

<Table>

Textbook Question

a. What is the equilibrium constant for a reaction that is carried out at 25 °C (298 K) with ∆H° = 20 kcal/mol and ∆S° = 5.0 * 10 - 2 kcal mol -1K-1?

b. What is the equilibrium constant for the same reaction carried out at 125 °C?

Textbook Question

(ii) Which side of the reaction is favored by entropy? (iii) If ∆S° = 0 for these reactions, calculate ∆G° (Assume T = 298 K) [BDE for O―H = 110 kcal /mol.] (b)

Textbook Question

For the following values of ∆H° , ∆S°, and T, tell whether the process would be favored. (b) ∆H° = +7.34 kcal/mol ; ∆S° = +43 cal/mol•K ; T = 325 K

Textbook Question

Considering the process described in Assessment 5.13, will it be favored or disfavored at a temperature higher than the one you calculated? How about at a temperature below what you calculated?

Textbook Question

For the following values of ∆H° , ∆S°, and T, tell whether the process would be favored.

(d) ∆H° = -8.3 kcal/mol ; AS° = -12 cal/mol•K ; T = 298 K

Textbook Question

Calculate ∆G°, ∆H°, and ∆S° for the following acid–base reactions. Rationalize the value of ∆H° based on the structure of the conjugate bases. [Assume T = 298 K.]

(b) <IMAGE>

Textbook Question

When ethene is treated in a calorimeter with H2 and a Pt catalyst, the heat of reaction is found to be -137 kJ/mol (-32.7 kcal/mol), and the reaction goes to completion.

When the reaction takes place at 1400°K, the equilibrium is found to be evenly balanced, with Keq=1.

Compute the value of ΔS for this reaction.

CH2=CH2 + H2 Pt catalyst⇌ CH3—CH3

ΔH= -137 kJ/mol (-32.7 kcal/mol)

Showing 31 of 31 practice