Objectives:
After having completed this unit, students should be able to:
- Define or explain and give an example of each of the following terms.
- spontaneous process
- state function (see pg 167)
- system
- surroundings
- reversible and irreversible processes
- Explain how entropy is related to randomness or disorder, positional probability, and the number of microstates available to the system.
- Predict whether a process is spontaneous.
- Predict the relative number of microstates available to a system under varying conditions, or using your understanding of the relative number of microstates available to systems predict whether entropy of a system increases or decreases.
- Predict the sign of the entropy change for a given process, phase change, or chemical reaction.
- Calculate ΔS° for a chemical reaction using the tabulated S° values of the reactants and products and a balanced equation.
- State and explain the second law of thermodynamics in terms of entropy. Understand the relationship of the entropy change in the system, surroundings, and universe to the second law.
- Explain the temperature dependence of entropy and predict how spontaneity can be affected by increasing or decreasing temperature.
- Given any two of the following variables, ΔS, ΔH or T calculate the third variable.
- Define free energy and relate it to spontaneity.
- Given ΔH, ΔS, and T, calculate the change in Gibbs Free Energy and then predict whether a process will be spontaneous.
- Define and write the equation for the standard free energy of formation, ΔGf° of a substance.
- Calculate ΔG°, ΔH° and ΔS° for a reaction from tabulated data.
- Given temperature and any two of the following variables, ΔS, ΔH or ΔG, calculate the third variable
- Explain how ΔG changes with a change in the concentration or partial pressure of reactants or products.
- Calculate ΔG given the concentration or partial pressures of reactants and products.
- Explain equilibrium in terms of minimum free energy and show how the value of K is related to free energy.
- Calculate ΔG° from K and vice-versa.
- Predict how ΔG° will change with temperature given ΔH° and ΔS°.
- Explain the relationship between the maximum work obtainable and the free energy change.
- Explain the relationship between kinetics and thermodynamics.
Reading and Homework Exercises
Table of Contents from: OpenStax Chemistry 2e:
- Chapter 5, section 5.3 (Review of Enthalpy and 1st Law of Thermodynamics)
- Chapter 16 – Thermodynamics
5.3 Enthalpy
Question 1:
Question 2:
Question 3:
For the reaction:
2 C6H6 (l) + 15 O2 (g) → 12 CO2 (g) + 6 H2O(g)
Using the data in Appendix G, answer the following questions:
Question 4:
Question 5:
Given the following data:
2Fe(s) + 3/2 O2(g) —-> Fe2O3(s) ΔH°= -822.2 kJ/mol
CO(g) + 1/2 O2(g) —-> CO2(g) ΔH°= -383.3 kJ/mol
Determine ΔH° for the reaction
Fe2O3(s) + 3CO(g) —-> 3CO2(g) + 2Fe(s)
16 Introduction
16.1 Spontaneity
16.2 Entropy
Question 6:
Question 7:
Question 8:
Question 9:
16.3 The Second and Third Laws of Thermodynamics
Question 10:
Question 11:
Question 12:
For the reaction C2H2(g) + 2 H2(g) → C2H6(g), answer the following question. Use data in Appendix G
Question 13:
For the reaction 2 BaO (s) → 2 Ba (s) + O2 (g), answer the following question. Use data in Appendix G
Question 14:
16.4 Free Energy
Question 15:
Question 16:
Question 17:
The boiling of an unknown compound X can be represented as follows:
X (l) → X (g)
ΔH° = 42.8 kJ/mol and ΔS° = 110.9 J/mol⋅K
Question 18:
Consider the reaction 3 CH4 (g) → C3H8 (g) + 2 H2 (g)
The reaction occurs at 25°C.
Using the data in Table 1, answer the following questions:
Table 1
Formula | ΔHf° (kJ/mol) | S° (J/mol⋅K) |
CH4 (g) | -74.6 | 186.3 |
C3H8 (g) | -103.8 | 270.3 |
H2 (g) | 0 | 130.7 |
Question 19:
Question 20:
Question 21:
Given the following data:
2Fe(s) + 3/2 O2(g) —-> Fe2O3(s) ΔG°= -742.2 kJ/mol
CO(g) + 1/2 O2(g) —-> CO2(g) ΔG°= -257.2 kJ/mol
Determine ΔG° for the reaction
Fe2O3(s) + 3CO(g) —-> 3CO2(g) + 2Fe(s)
Question 22:
Question 23:
Consider the reaction NH4Cl(g) → NH3 (g) + HCl (g)
The reaction occurs at 298 K.
Using the data in Table 2, answer the following questions:
Table 2
Formula | ΔHf° (kJ/mol) | ΔGf° (kJ/mol) |
NH3 (g) | -46.1 | -16.5 |
HCl (g) | -92.3 | -95.3 |
NH4Cl(g) | -314.4 | -203 |
Question 24:
Question 25:
Consider the reaction Ca(OH)2 (s) ↔ Ca2+ (aq) + 2 OH– (aq)
The reaction occurs at 25°C. For [Ca2+] = 1.5 M and pOH = 8.00 , and using ΔGf° data from Appendix G answer the following questions:
Question 26:
Consider the reaction HC2H3O2 (aq) ↔ H+ (aq) + C2H3O2– (aq)
The reaction occurs at 25°C. Using the Ka data in Appendix H, answer the following questions:
Question 27: