I am not acquainted with a frost diagram. If it isn't too complex, I'd like to know about themmjc123 said:Why do you reverse the second equation? Add equation 1 to equation 2 and what do you get?
PS Are you familiar with oxidation state diagrams (also called Frost diagrams)? Drawing one for Fe may help.
Alright, so adding both reactions gives us the desired reaction. But how do we obtain the result that the sum of their free energies is equal to the free energy of the reaction obtained by adding them? Also, why can't we simply add the E values as well like we do for a cell by summing cathode and anode reaction E valuesmjc123 said:Why do you reverse the second equation? Add equation 1 to equation 2 and what do you get?
PS Are you familiar with oxidation state diagrams (also called Frost diagrams)? Drawing one for Fe may help.
Have you heard of Hess's law?Krushnaraj Pandya said:But how do we obtain the result that the sum of their free energies is equal to the free energy of the reaction obtained by adding them?
Free energies are additive. Potentials are not. They are related by ΔG = -nFE. SoKrushnaraj Pandya said:Also, why can't we simply add the E values as well like we do for a cell by summing cathode and anode reaction E values
I thought Hess's Law was for Enthalpies onlymjc123 said:Have you heard of Hess's law?
G is a state function, so the difference in G between two states is independent of the path taken between them. So it doesn't matter whether you go from Fe3+ to Fe directly, or via Fe2+ as an intermediate - the free energy change is the same.
Free energies are additive. Potentials are not. They are related by ΔG = -nFE. So
ΔG3 = ΔG1 + ΔG2
implies 3E3 = E1 + 2E2
A Frost diagram would show this clearly (google "Frost diagram"). It is a graph with oxidation number as the x-axis and free energy as the y axis. The difference in free energy (y-coordinate) between two states is nFE; the slope of the line joining them is FE (where E is the reduction potential; note positive progression along the x-axis means oxidation, so a positive slope means positive ΔGox, i.e. negative Eox, i.e. positive Ered.)
Alright, so E is not a state function. But G=-nFE, and G is a state function.mjc123 said:Strictly speaking, perhaps, but the principle applies for all state functions.
The standard reduction potential of Fe is a measure of the tendency of iron (Fe) to gain electrons and become reduced in a redox reaction, compared to a standard hydrogen electrode (SHE) at standard conditions (25°C, 1 atm pressure, and 1 M concentration of ions).
The standard reduction potential of Fe is typically determined experimentally by measuring the potential difference between a standard hydrogen electrode and a solution containing Fe ions at standard conditions, using a voltmeter. The potential difference gives the standard reduction potential of Fe.
The standard reduction potential of Fe is important because it allows scientists to predict the direction of a redox reaction involving Fe, as well as the voltage and energy changes associated with the reaction. It also provides information about the reactivity and stability of Fe in different environments.
The standard reduction potential of Fe is affected by the pH of the solution. As the pH increases, the standard reduction potential of Fe becomes more positive, indicating that Fe is more likely to be reduced. Conversely, as the pH decreases, the standard reduction potential becomes more negative, indicating that Fe is more likely to be oxidized.
The standard reduction potential of Fe can be influenced by several factors such as temperature, concentration of ions, and the presence of other substances in the solution. Changes in these factors can shift the equilibrium of the redox reaction and therefore affect the standard reduction potential of Fe.