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Solutions and Electrochemistry IV (Activty a_x (a_x = gamma [x] (gamma is…
Solutions and Electrochemistry IV
Electrode Potential and emf
Must subtract anode emf from cathode emf
Don't forget that anode has negative reduction potential (as it is oxidised)
Nernst Equation
Activty a_x
Effective concentration of species in a mixture
Always less than concentration of solution
Arises by intermolecular interactions in non-ideal gases/solutions
a_x = gamma [x]
gamma is dimensionless activity coefficient
Gamma approximates to 1 in dilute solutions
In more concentrated solutions, gamma decreases as there is more intermolecular interaction
Cannot measure gamma + and gamma - (mean individual ion coefficients) in isolation!
Debye-Huckel Laws
Limiting Law
For 0.001 < l < 0.1 molal
is mean ion activity coefficient
I is ionic strength
A is solvent dependent constant
B and a are given constants
Extended Law
For l < 0.001 molal
Ionic Strength
Calculate the ionic strenght of a 10^-4 solution of magnesium nitrate.
Calculate the mean ion activity coefficient of this solution.
Calculate the activity of this solution
