Electrochemistry

Question 1

Faraday’s First Law

Answer 1

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

Question 2

Faraday’s 2nd law

Answer 2

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

Question 3

One Faraday

Answer 3

1 Faraday is the charge carried by 1 mole of electrons

F= Avogadro’s number x e-

1F= 96500 C

Question 4

Galvanic cell

Answer 4

Device in which chemical energy is converted into electrical energy

Question 5

Function of salt bridge

Answer 5

1. Completes the electrical circuit by allowing the ions to flow from one half cell to another half cell
2. Maintains the electrical neutrality of the solution present in the two cells

Question 6

Electrode potential

Answer 6

Tendency of the electrode to lose or gain ions when in contact with a solution of its own ions is called electrode potential

Question 7

Standard electrode potential conditions

Answer 7

1. temperature: 298 K
2. conc of ions- 1 mol/L
3. pressure- atm

Question 8

Standard hydrogen electrode (SHE)

Answer 8

1. Electrode potential- 0V
2. Hydrogen gas absorbed in an inert platinum electrode
3. Standard conditions- 298 K, 1 atm, 1 mo/L
4. acts as both cathode and anode

Question 9

Electrochemical series

Answer 9

Arrangement of various electrode systems in increasing order of their standard reduction potentials

Question 10

grw reactivity of metals decreases in going down the electrochemical series

Answer 10

The tendency of the substances to get oxidised decreases from top to bottom so reactivity decreases

Question 11

comment on the feasibility of reaction
1. E^0= +ve
2. E^0= 0
3. E^0= -ve

Answer 11

1. Feasible
2. In equilibrium
3. not feasible

Question 12

when is a reaction feasible

Answer 12

When reduction potential of the cathode is higher than that of the anode

Question 13

grw electropositive character reduces in going down the series

Answer 13

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

Question 14

Negative free energy

Answer 14

System does electrical work on the surroundings

Question 15

EMF of galvanic cell

Answer 15

difference of electrode potential which causes the flow of current from one electrode to another when virtually no current is drawn

Question 16

Positive free energy

Answer 16

No electrical work is done by the system
Cell reaction will not occur

Question 17

Electrical conductivity

Answer 17

Ease of flow of current through a conductor is called electrical conductivity

Question 18

Specific resistance

Answer 18

Resistance offered per unit length and per unit cross sectional area when a voltage is applied

Question 19

Conductance

Answer 19

Ease with which electrons can pass in a conductor

Question 20

Specific conductivity or conductivity (K)

Answer 20

Conductance of 1cm^3 of the solution

Question 21

Equivalent conductance

Answer 21

Conductance of 1 gm equivalent of an electrolyte in given concentration of solution

Question 22

Molar conductance

Answer 22

Conductance of one mole of an electrolyte in given concentration of solution

Question 23

Cell constant

Answer 23

Ratio of distance of electrode and closed area

G * = l/A

Question 24

infinite dilution / zero concentration / limiting molar conductivity

Answer 24

the limiting value of molar conductivity when concentration approaches zero
value beyond which molar conductivity will not increase

Question 25

Kohlrausch’s law

Answer 25

The molar conductivity at infinite dilution of an electrolyte is equal to the sum of molar conductances of its cations and anions, with each conductance term multiplied by the number of ions present in the electrolyte