Equations Topic 9/19

Question 1

Cell potentials

Answer 1

Eθcell = Eθ (reduction) - Eθ (oxidation)

where
Eθ = reduction potential at STP

**if cell potential is (-), the reaction is not spontaneous. If (+), the reaction is spontaneous

Question 2

Relation between G and E

Answer 2

ΔGθ = -n F Eθcell

where
ΔGθ = change in Gibbs free energy at SATP (if + = non-spontaneous reaction, if 0 = equilibrium, if - = spontaneous)
n = number of electrons transferred per reaction
F = Faraday’s constant
Eθcell = standard electron potential of the cell (if + = spontaneous reaction

Question 3

Mass deposited on cathode

Answer 3

Q = It
n (e-) = Q / F
n (deposit) = n (e-) / z
m (deposit) = n (deposit) x M
=> m (deposit) = MIt / zF

where
Q = charge
I = current
t = time
n = number of electrons transferred per reaction
F = Faraday’s constant
z = stoichiometric coefficient
m = mass
M = molar mass