Lecture 7 Flashcards
What is the extent of a reaction? How does it represent the amount of substance in a reaction?
the extent of the reaction (ع) is a value with dimensions of the amount of substances (in mol), representing the infinitesimal change of one substance to another.
the said change in the amount of species is represented by ع in the equation:
V * dع
where v is the stoichiometric number of the species (positive for products, negative for reactants)
How is the gibbs energy of reaction redefined in terms of the extent of the reaction? Drive this expression
It is defined as the slope of the Gibbs energy plotted against the extent of the reaction(ع).
∆rG = (δG/δع)
The derivation is found in notes on page 1
What is an exergonic and endergonic reactions?
The exergonic reaction is a reaction that has a ∆rG < 0, in which the reaction is spontaneous and therefore it can be used to drive another process, such as a reaction, or used to do non-expansion work.
The endergonic reaction is a reaction that has a ∆rG > 0, in which the reaction is not spontaneous and can only occur by doing work on it
What is the derivation for the Gibbs energy in relation to the partial pressure of gases and in equilibrium? (Explain all conditions and the steps used)
Found in notes on pages 1-2.
How is gibbs minimum energy (at eq) shown by the mixing of two gases?
Found within old notes, the same concept just now we know that the mixing graph is represented by ∆mixG = nRT(xa ln(xa) +xb ln(xb))
What is the derivation of Gibbs energy at any arbitrary stage?
Found in notes on pages 2-4
What is the response of the equilibrium constant to pressure?
First off from the fact that the eq constant depends on (∆rG^o) which is defined at a set constant pressure then we already know that the eq constant is 9ndepentent of said pressure where (δk/δp)T = 0
Having said that it doesn’t mean the variation of pressure cannot affect the eq composition.
One way we can think about increasing the gas is by adding an inert gas to the volume mixture but considering that the gases are perfect they won’t interact with each other which then means that all the values of partial pressure would be the same and the overall pressure would not change when adding an inter gas to a (perfect) gas mixture.
Alternatively, if we change the volume that said gases are in, the pressure of the system might change. Although the eq constant, K, will remain constant the partial pressures of the gases that K depends on will change but in a way that keeps K constant.
This change of pressure would either push the eq towards the reactants or the products where following Henri Le Chatelier principle, decreasing the volume (i.e increasing the pressure) pushes the eq towards the side with fewer molecules
A mathematical example of how this works is found in notes on pages 4-5
What is the derivation to the Van’t Hoff equation to show the eq constant response to temp?
Found in notes on pages 5-6
How is the Van’t Hoff equation used and how can we draw a graph from it)
Page 6 notes
