Download presentation

Presentation is loading. Please wait.

Published bySkylar Bence Modified over 3 years ago

5
We will call μ the Chemical Potential Right now we will think of it as the molar free energy, but we will refine this definition later… Free Energy of a Gas Define the molar Gibbs free Energy, μ: Pseudo-definition

7
Note: this is a little sloppy: Really: μ(T,p) = μ 0 (T) + RT ln (p/p 0 ) (argument of ln dimensionless) I (and many others) will continue to be sloppy in this regard, so remember p is in the units defined by the Standard State !!! The above holds for an Ideal Gas, Only!!!

8
We can now use any relation that we derive for an ideal gas mixture for real gases --- just replace p with f everywhere. f (the effective pressure) cannot be read on a gauge but must be evaluated from an EOS! Standard state

11
Chemical Reactions and Free Energy

14
Holds for any ideal mixture, not just gases

19
For an IDEAL MIXTURE (even liquids/solids) : G mix is solely the result of the increase in Entropy! H mix = 0 V mix = 0 Danger! This is not always the case: (Ethanol/Water for example)

28
Important Features of the Equilibrium Constant The Equilibrium Constant is a function of temperature only All pure phases are ignored in the Equilibrium expression (exact) The concentration of the solvent is ignored in solution equilibrium (approximation) The Equilibrium Constant is taken as a dimensionless number with all concentration values referenced to a standard state (Standard state arbitrary but its choice has numerical consequence)

29
Consider any reaction (even solution phase) whose constituents can be considered an ideal mixture aA + bB cC + dD The free energy change will be: where At equilibrium, G=0 and KQ Which defines the equilibrium expression or

30
In analogy to what we did for real gases, we can define an effective concentration for real solutions called the activity, and replace the concentration with it everywhere

31
A note on K C and K p : The equilibrium constant is taken as a dimensionless number that is a function of temperature only. Since there are no units, we must be careful to reference the proper definition of concentration (molecular number density). For gases, the concentration may be quoted as pressure (atm) or molarity (mol/l). If the standard of concentration is 1 mol/L, we say the equilibrium constant is K C, if the standard is 1 atm pressure, the equilibrium constant is labeled K p Recall the definition of K C: The proper quotient of equilibrium partial pressures, assuming the ideal gas equation of state (pV=nRT) (only choice, really) is:

32
Therefore, the numerical value of the equi8librium constant depends on the choice of standard state and the temperature through a difference in the number of gas phase moles between products and reactants:

33
Recall The temperature Dependence of G??

50
Fin

Similar presentations

OK

Calculating Equilibrium Composition Example Cl 2 (g) → 2Cl (g)

Calculating Equilibrium Composition Example Cl 2 (g) → 2Cl (g)

© 2018 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on structure of human respiratory system Ppt on railway track Ppt on coffee shop business plan Ppt on fibonacci numbers nature Ppt on personal financial planning Download ppt on civil disobedience movement in civil rights Ppt on condition based maintenance certification Ppt on do's and don'ts of group discussion videos Ppt on wild animals Ppt on history of indian railways