electrochem formulae

Question 1

cell potential

Answer 1

cathode - anode

Question 2

enthalpy of solution

Answer 2

lattice enthalpy + hydration enthalpy

Question 3

molar conductivity

Answer 3

Λ = k/c

Question 4

ksp (AB)

Answer 4

a(A+) a(B-)

Question 5

what is ɛ_0

Answer 5

the vacuum permittivity

Question 6

what is e in coulomb potential

Answer 6

elementary charge of an e-

Question 7

what is ɛ_r

Answer 7

relative permittivity (the reduction of an electrostatic field from the presence of solvent)

Question 8

for the ionic strength eq what is important to remember?

Answer 8

the ^2 at the end only applies to the z value (the charge)

Question 9

eq for electrical work?

Answer 9

J = V * q

where V = potential difference, q = charge transferred

Question 10

why does the nernst eq have a negative n

Answer 10

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

Question 11

what is the temp coefficient of the cell?

Answer 11

(∂E / ∂T)_p

Question 12

what is the form of the nernst eq for electrodes of second kind?

Answer 12

E = E^0 * - RT/F ln (a(anion))

Question 13

what is k in the molar conductivity eq?

Answer 13

conductivity = the reciprocal of resistivity

Question 14

electrophoretic mobility

Answer 14

μ = ze/f

where f =6πrn

Question 15

eq for transport number

Answer 15

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

Question 16

what is k for M+/X-, M2+/X2+, M3+/X3+, M4+/X4+ ?

Answer 16

the number squared e.g. 4^2 = 16

Question 17

what is n in the nernst eq?

Answer 17

the no. of e- from the half eq of the cell

Question 18

eq for pH

Answer 18

-log [H+]

Question 19

what is Q?

Answer 19

conc of products/conc reactants

Question 20

Why are J and deltaG equal?

Answer 20

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

Question 21

eq for specific energy

Answer 21

VIt/m

Question 22

eq for specific power

Answer 22

VxI/m

Question 23

eq for theoretical specific capacity

Answer 23

q_th = nF/Mr

Question 24

what is theoretical specific capacity?

Answer 24

amount of charge per kg of reactants

Question 25

eq for coulombic efficiency

Answer 25

qpr/qth

Question 26

how to convert the units of As/g for qth to Ah/kg

Answer 26

divide by 3.6

Question 27

eq for power delivered

Answer 27

P = iE

Question 28

eq for surface tension

Answer 28

λ = ∂G/∂A

Question 29

eq to estimate surface tension by stretching a thin water film?

Answer 29

dG = fdx = ydA

Question 30

young-laplace equation for bubbles

Answer 30

pin = pout + 2 Y/r
OR
for bubbles deltaP = 2 Y/r

Question 31

contact angle and young eq

Answer 31

YSG = YSL + YLG cos theta -> cos theta = YSG-YSL/YLG

Question 32

What values to use for standard conditions for Nernst calculations?

Answer 32

All concentrations of 1M, assume an activity of 1, 298K, Q =1 if in the standard state

Question 33

In what cases can you simplify the reaction quotient equation to concentrations instead of activities?

Answer 33

For most purposes but especially non-acidic electrochemical cells working at low (<1M) concentrations