Electrochemistry Flashcards
Faraday’s First Law
Weight of the substance liberated or deposited at any electrode is directly proportional to the quantity of charge flowing through it
W= zIT
W= wt of substance
I= current
t= time in seconds
z= electrochemical equivalent
Faraday’s 2nd law
If the same amount of current is passed through two different electrolytes connected in series then the weight of the substance liberated is directly proportional to their equivalent masses
One Faraday
1 Faraday is the charge carried by 1 mole of electrons
F= Avogadro’s number x e-
1F= 96500 C
Galvanic cell
Device in which chemical energy is converted into electrical energy
Function of salt bridge
- Completes the electrical circuit by allowing the ions to flow from one half cell to another half cell
- Maintains the electrical neutrality of the solution present in the two cells
Electrode potential
Tendency of the electrode to lose or gain ions when in contact with a solution of its own ions is called electrode potential
Standard electrode potential conditions
- temperature: 298 K
- conc of ions- 1 mol/L
- pressure- atm
Standard hydrogen electrode (SHE)
- Electrode potential- 0V
- Hydrogen gas absorbed in an inert platinum electrode
- Standard conditions- 298 K, 1 atm, 1 mo/L
- acts as both cathode and anode
Electrochemical series
Arrangement of various electrode systems in increasing order of their standard reduction potentials
grw reactivity of metals decreases in going down the electrochemical series
The tendency of the substances to get oxidised decreases from top to bottom so reactivity decreases
comment on the feasibility of reaction
1. E^0= +ve
2. E^0= 0
3. E^0= -ve
- Feasible
- In equilibrium
- not feasible
when is a reaction feasible
When reduction potential of the cathode is higher than that of the anode
grw electropositive character reduces in going down the series
the metals on top have the highest tendency to get oxidised i.e. gain electrons which is a characteristic of metals which are more electropositive
as we go down the series, reducing power decreases so electropositive character also decreases
Negative free energy
System does electrical work on the surroundings
EMF of galvanic cell
difference of electrode potential which causes the flow of current from one electrode to another when virtually no current is drawn
Positive free energy
No electrical work is done by the system
Cell reaction will not occur
Electrical conductivity
Ease of flow of current through a conductor is called electrical conductivity
Specific resistance
Resistance offered per unit length and per unit cross sectional area when a voltage is applied
Conductance
Ease with which electrons can pass in a conductor
Specific conductivity or conductivity (K)
Conductance of 1cm^3 of the solution
Equivalent conductance
Conductance of 1 gm equivalent of an electrolyte in given concentration of solution
Molar conductance
Conductance of one mole of an electrolyte in given concentration of solution
Cell constant
Ratio of distance of electrode and closed area
G * = l/A
infinite dilution / zero concentration / limiting molar conductivity
the limiting value of molar conductivity when concentration approaches zero
value beyond which molar conductivity will not increase
