Chemistry > Thermodynamics and Thermochemistry > 19.0 Enthalpy, Entropy, Free Energy Changes and The Nature of Process
Thermodynamics and Thermochemistry
1.0 Introduction to Thermodynamics
1.1 Importance of Thermodynamics
1.2 Limitations of Thermodynamics
1.3 Some Basic Terms of Thermodynamics
2.0 Thermodynamic Processes
2.1 Some other important relations of adiabatic process
2.2 Reversible and Irreversible Processes
2.3 Polytropic Process
3.0 Heat $(Q)$
4.0 Work $(W)$
5.0 Internal Energy
6.0 Zeroth Law of Thermodynamic
7.0 First Law of Thermodynamics
8.0 Heat Capacity
9.0 Enthalpy $(H)$ or Heat Content
10.0 Significance of $?H$ and $?E$
11.0 Relationship Between $?H$ and $?E$
12.0 Standard Enthalpy of Reaction
12.1 Molar Enthalpy of Fusion $\left( {\Delta {H_{fus}}} \right)$
12.2 Molar Enthalpy of Vaporisation $(\Delta {H_{vap}})$
12.3 Enthalpy of Sublimation $\left( {\Delta {H_{sub}}} \right)$
12.4 Enthalpy of Formation
12.5 Enthalpy of Combustion $\left( {\Delta {H_c}} \right)$
12.6 Enthalpy of Neutralization $\left( {\Delta {H_{neu}}} \right)$
12.7 Enthalpy of Solution $\left( {\Delta {H_{sol}}} \right)$
13.0 Law of Thermodynamics
14.0 Bond Energy or Bond Enthalpies
15.0 Second Law of Thermodynamic
16.0 Entropy (S)
16.1 Some Important points Related to Entropy
16.2 Entropy Change in Various Thermodynamic Process
16.3 Entropy Change in Phase Transformation
17.0 Spontaneous Processes
18.0 Free Energy (G)
19.0 Enthalpy, Entropy, Free Energy Changes and The Nature of Process
20.0 Standard Free Energy Change
21.0 Coupled Reactions
22.0 Third Law of Thermodynamic
22.1 Third Law of Thermodynamics, Entropy ? Temperature
22.2 Limitations of Third Law of Thermodynamics
23.0 Important Facts
19.1 Characteristics of Free Energy
1.2 Limitations of Thermodynamics
1.3 Some Basic Terms of Thermodynamics
2.2 Reversible and Irreversible Processes
2.3 Polytropic Process
12.2 Molar Enthalpy of Vaporisation $(\Delta {H_{vap}})$
12.3 Enthalpy of Sublimation $\left( {\Delta {H_{sub}}} \right)$
12.4 Enthalpy of Formation
12.5 Enthalpy of Combustion $\left( {\Delta {H_c}} \right)$
12.6 Enthalpy of Neutralization $\left( {\Delta {H_{neu}}} \right)$
12.7 Enthalpy of Solution $\left( {\Delta {H_{sol}}} \right)$
16.2 Entropy Change in Various Thermodynamic Process
16.3 Entropy Change in Phase Transformation
22.2 Limitations of Third Law of Thermodynamics
• It is a thermodynamic state function
• It is represented by $‘G’.$
$$G=H-TS$$
Gibbs free energy change at constant temperature
$$\Delta G = \Delta H - T\Delta S$$
• It is an extensive property since its value depends upon the quantity of substance.
• Criteria of spontaneity based on constant $T$ and $P.$
(a) If $\Delta G < 0,$ the process is spontaneous
(b) If $\Delta G > 0,$ the process is non-spontaneous
(c) If $\Delta G = 0$ the system is at equilibrium
• $\Delta G$ is equal to maximum possible useful work other than the $P-V$ work that is obtainable from the system.
• $\Delta G = - NF\;{E_{cell}}$
• $\Delta G^\circ = - nF\;E{^\circ _{cell}}$ where $E_{cell}^\circ $ $=$ standard cell potential.
• The relation between Gibb’s free energy change and equilibrium constant.
$$\Delta G = \Delta {G^\circ } + \frac{{RT}}{{\ln Q}}$$
At equilibrium $?G = 0$
$$\therefore \quad \Delta {G^\circ } = - RT\;\ln \;K = - 2.303\;RT\;\log \;K\quad ....(1)$$
Again
$$\therefore \quad \Delta {G^\circ } = \Delta {H^\circ } - T\Delta {S^\circ }$$
• At equilibrium $?G = 0$
So $$\Delta H - T\Delta S = 0\quad or\quad T\Delta S = \Delta H$$
$$T = \frac{{\Delta H}}{{\Delta S}}$$
