electrochem formulae Flashcards
cell potential
cathode - anode
enthalpy of solution
lattice enthalpy + hydration enthalpy
molar conductivity
Λ = k/c
ksp (AB)
a(A+) a(B-)
what is ɛ_0
the vacuum permittivity
what is e in coulomb potential
elementary charge of an e-
what is ɛ_r
relative permittivity (the reduction of an electrostatic field from the presence of solvent)
for the ionic strength eq what is important to remember?
the ^2 at the end only applies to the z value (the charge)
eq for electrical work?
J = V * q
where V = potential difference, q = charge transferred
why does the nernst eq have a negative n
n is the no. of moles of e-, neg shows that the cell is performing work on the surroundings, = a spontaneous reaction with Ecell > 0 and deltaG < 0
what is the temp coefficient of the cell?
(∂E / ∂T)_p
what is the form of the nernst eq for electrodes of second kind?
E = E^0 * - RT/F ln (a(anion))
what is k in the molar conductivity eq?
conductivity = the reciprocal of resistivity
electrophoretic mobility
μ = ze/f
where f =6πrn
eq for transport number
cation = t+ = z+cLAF/I delta t = I+/I
where L = B-A = distance moved by the boundary in the time
A = cross-section of the tube
I = total electric current passed
what is k for M+/X-, M2+/X2+, M3+/X3+, M4+/X4+ ?
the number squared e.g. 4^2 = 16
what is n in the nernst eq?
the no. of e- from the half eq of the cell
eq for pH
-log [H+]
what is Q?
conc of products/conc reactants
Why are J and deltaG equal?
DeltaG is the maximum work done by a system and in a galvanic cell the chemical energy is converted to electrical energy which is used to do work
So deltaG = Wmax = Wele = J
eq for specific energy
VIt/m
eq for specific power
VxI/m
eq for theoretical specific capacity
q_th = nF/Mr
what is theoretical specific capacity?
amount of charge per kg of reactants
eq for coulombic efficiency
qpr/qth
how to convert the units of As/g for qth to Ah/kg
divide by 3.6
eq for power delivered
P = iE
eq for surface tension
λ = ∂G/∂A
eq to estimate surface tension by stretching a thin water film?
dG = fdx = ydA
young-laplace equation for bubbles
pin = pout + 2 Y/r
OR
for bubbles deltaP = 2 Y/r
contact angle and young eq
YSG = YSL + YLG cos theta -> cos theta = YSG-YSL/YLG
What values to use for standard conditions for Nernst calculations?
All concentrations of 1M, assume an activity of 1, 298K, Q =1 if in the standard state
In what cases can you simplify the reaction quotient equation to concentrations instead of activities?
For most purposes but especially non-acidic electrochemical cells working at low (<1M) concentrations
