Chapter - 4 Electrochemistry Class 12 Notes | EduRev

Chemistry Class 12

Class 12 : Chapter - 4 Electrochemistry Class 12 Notes | EduRev

The document Chapter - 4 Electrochemistry Class 12 Notes | EduRev is a part of the Class 12 Course Chemistry Class 12.
All you need of Class 12 at this link: Class 12

ELECTRODE POTENTIAL
For any electrode → oxidiation potential = - Reduction potential
Ecell = R.P of cathode - R.P of anode
Ecell = R.P. of cathode + O.P of anode
Ecell is always a +ve quantity & Anode will be electrode of low R.P
Cell = SRP of cathode - SRP of anode.

  •  Greater the SRP value greater will be oxidising power.

GIBBS FREE ENERGY CHANGE :
ΔG = - nFEcell
ΔG° = - nFE°cell

NERNST EQUATION : (Effect of concentration and temp of an emf of cell)
⇒ ΔG = ΔG° + RT lnQ (where Q is raection quotient)
ΔG° = - RT ln Keq

Chapter - 4 Electrochemistry Class 12 Notes | EduRev
At chemical equilibrium
ΔG = 0 ; ECell = 0.

  •  Chapter - 4 Electrochemistry Class 12 Notes | EduRev
    Chapter - 4 Electrochemistry Class 12 Notes | EduRev
    For an electrode M(s)/Mn+.
    Chapter - 4 Electrochemistry Class 12 Notes | EduRev

CONCENTRATION CELL : A cell in which both the electrods are made up of same material.
For all concentration cell E°cell = 0.
(a) Electrolyte Concentration Cell :
eg. Zn(s) / Zn2+ (c1) || Zn2+(c2) / Zn(s) Chapter - 4 Electrochemistry Class 12 Notes | EduRev

(b) Electrode Concentration Cell:
eg. Pt, H2(P1 atm) / H+ (1M) / H2(P2atm) / Pt Chapter - 4 Electrochemistry Class 12 Notes | EduRev


DIFFERENT TYPES OF ELECTRODES :
1. Metal-Metal ion Electrode M(s)/Mn+. Mn+ + ne- →  M(s) Chapter - 4 Electrochemistry Class 12 Notes | EduRev

2. Gas-ion Electrode Pt/H2(Patm)/H+(XM) as a reduction electrode Chapter - 4 Electrochemistry Class 12 Notes | EduRev
3. Oxidation-reduction Electrode Pt / Fe2+, Fe3+ as a reduction electrode Fe3+ + e- → Fe2+ Chapter - 4 Electrochemistry Class 12 Notes | EduRev
4. Metal-Metal insoluble salt Electrode eg. Ag/AgCI, Cl- as a reduction electrode AgCI(s) + e- → Ag(s) + Cl-
Chapter - 4 Electrochemistry Class 12 Notes | EduRev


CALCULATION OF DIFFERENT THERMODYNAMICS FUNCTION OF CELL REACTION

  • ΔG = -n FEcell
  • Chapter - 4 Electrochemistry Class 12 Notes | EduRev (At costant pressure).
  • Chapter - 4 Electrochemistry Class 12 Notes | EduRev
  • Chapter - 4 Electrochemistry Class 12 Notes | EduRev = Temperature cofficient of e.m.f of the cell.E = a + bT + CT2 + ....
  • Chapter - 4 Electrochemistry Class 12 Notes | EduRev
  • ΔCp of cell reaction
    Chapter - 4 Electrochemistry Class 12 Notes | EduRev
    Chapter - 4 Electrochemistry Class 12 Notes | EduRev

ELECTROLYSIS :
(a) Chapter - 4 Electrochemistry Class 12 Notes | EduRev

(b) Similarly the an ion which is strogner reducing agent(low value of SRP) is liberated fir stat the anode.
Chapter - 4 Electrochemistry Class 12 Notes | EduRev


FARADAY’S LAW OF ELECTROLYSIS :
First Law :
Chapter - 4 Electrochemistry Class 12 Notes | EduRev

Second Law :
W α E  W/E = constant Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Chapter - 4 Electrochemistry Class 12 Notes | EduRev

CURRENT EFFICIENCY = Chapter - 4 Electrochemistry Class 12 Notes | EduRev

  • CONDITION FOR SIMULTANEOUS DEPOSITION OF Cu & Fe AT CATHODE
    Chapter - 4 Electrochemistry Class 12 Notes | EduRevCondition for the simultaneous deposition of Cu & Fe on cathode.

CONDUCTANCE:

  • Chapter - 4 Electrochemistry Class 12 Notes | EduRev
  • Specific conductance or conductivity :
    (Reciprocal of specific resistance) k = 1/ρ K = specific conductance
  • Equivalent conductance:
    Chapter - 4 Electrochemistry Class 12 Notes | EduRev unit: -ohm-1 cm2 eq-1
  • Molar conductance:
    Chapter - 4 Electrochemistry Class 12 Notes | EduRev unit: -ohm-1 cm2 mole-1
    specific conductance = conductance x l/a

KOHLRAUSCH’S LAW:
Variation of λeqM of a solution with concentration :
(i) Strong electrolyte
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
(ii) Weak electrolytes :Chapter - 4 Electrochemistry Class 12 Notes | EduRev where λ is the molar conductivity

n+ = No of cations obtained after dissociation per formula unit
n_ = No of anions obtained after dissociation per formula unit

APPLICATION OF KOHLRAUSCH LAW:
1. Calculation of λ0M of weak electrolytes :
Chapter - 4 Electrochemistry Class 12 Notes | EduRev

2. To calculate degree of diossociation of a week electrolyte
Chapter - 4 Electrochemistry Class 12 Notes | EduRev

3. Solubility (S) of sparingly soluble salt & their Ksp

Chapter - 4 Electrochemistry Class 12 Notes | EduRev

IONIC MOBILITY: It is the distance travelled by the ion per second under the potential gradient of 1 volts per cm. It’s unit is cm2s-1v-1.

Absolute ionic mobility:
Chapter - 4 Electrochemistry Class 12 Notes | EduRev

Chapter - 4 Electrochemistry Class 12 Notes | EduRev

Transport Number:
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Where tc = Transport Number of cation & ta = Transport Number of anion


SOLUTION & COLLIGATIVE PROPERTIES
1. OSMOTIC PRESSURE :

(i) π = ρgh
Where, ρ = density of soln., h = equilibrium height.
(ii) Vont - Hoff Formula (For calculation of O.P.)
π = CST
π = CST = n/V (RT) (just like ideal gas equation)

∴ C = total cone, of all types of particles.
= C1 + C2 + C3 + ....
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Note : If V1 mL of C1 cone. + V2 mL of C2 cone, are mixed.
Chapter - 4 Electrochemistry Class 12 Notes | EduRev ; Chapter - 4 Electrochemistry Class 12 Notes | EduRev

Type of solutions:
(a) Isotonic solution 
- Two solutions having same O.P.
π1 = π2 (at same temp.)
(b) Hyper tonic - If π1> π2. ⇒ Ist solution is hypertonic solution w.r.t. 2nd solution.
(c) Hypotonic - IInd solution is hypotonic w.r.t. Ist solution.


Abnormal Colligative Properties : (In case of association or dissociation)
VANT HOFF CORRECTION FACTOR (i):

Chapter - 4 Electrochemistry Class 12 Notes | EduRev

  • i > 1 ⇒ dissociation.
    i < 1 ⇒ association.
  • Chapter - 4 Electrochemistry Class 12 Notes | EduRev
    ∴ π = iCRT
    π = (i1C1 + i2C2 + i3C3.....) RT

Relation between i & α (degree of dissociation) :
i = 1 + (n - 1)α Where, n = x + y.
Relation b/w degree of association β & i.
Chapter - 4 Electrochemistry Class 12 Notes | EduRev

2. RELATIVE LOWERING OF VAPOUR PRESSURE (RLVP) :
Vapour pressure : PSoln. < P
Lowering in VP = P - Ps = ΔP
Relative lowering in vapour pressure Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Raoult's law :- (For non - volatile solutes)
Experimentally relative lowering in V.P = mole fraction of the non volatile solute in solutions.
Chapter - 4 Electrochemistry Class 12 Notes | EduRev

Chapter - 4 Electrochemistry Class 12 Notes | EduRev

Chapter - 4 Electrochemistry Class 12 Notes | EduRev (M = molar mass of solvent)
If solute gets associated or dissociated
Chapter - 4 Electrochemistry Class 12 Notes | EduRev

  • According to Raoult’s law
    (i) Chapter - 4 Electrochemistry Class 12 Notes | EduRev where X1 is the mole fraction o f the solvent (liquid).
    (ii) An alternate form → Chapter - 4 Electrochemistry Class 12 Notes | EduRev
  • Ostwald—Walker Method : Experimental or lab determination of Chapter - 4 Electrochemistry Class 12 Notes | EduRev
    Chapter - 4 Electrochemistry Class 12 Notes | EduRev

3. ELEVATION IN BOILING POINT :
ΔTb = i x Kbm
Chapter - 4 Electrochemistry Class 12 Notes | EduRev or Chapter - 4 Electrochemistry Class 12 Notes | EduRev

Chapter - 4 Electrochemistry Class 12 Notes | EduRev

4. DEPRESSION IN FREEZING POINT:
∴ ΔT= i x Kf . m.
K= molal depression constant = Chapter - 4 Electrochemistry Class 12 Notes | EduRev

RAOULT’S LAW FOR BINARY (IDEAL) MIXTURE OF VOLATILE LIQUIDS :
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
xA' = mole fraction of A in vapour about the liquid / solution.
xB' = mole fraction of B
Chapter - 4 Electrochemistry Class 12 Notes | EduRev

Graphical Representation :

Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Ideal solutions (mixtures) : Mixtures which follow Raoul'ts law at all temperature.
Chapter - 4 Electrochemistry Class 12 Notes | EduRev

ΔHmix = 0 ΔVmix = 0 ΔSmix = + ve as for process to proceed : ΔGmix = -ve
eg. (1) Benzene + Toluene. 

(2) Hexane + heptane. 

(3) C2H5Br + C2H5I.
Non - Ideal solutions : Which do not obey Raoult's law.

(a) Positive deviation :-
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
eg. H2O + CH3OH.
H2O + C2H5OH
C2H6OH + hexane
C2H5OH + cyclohexane.
CHCI3 + CCI4 → dipole dipole interaction becomes weak.
Chapter - 4 Electrochemistry Class 12 Notes | EduRev

(b) Negative deviation
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
e.g. H2O + HCOOH
H2O + CH3COOH
H2O + HNO3
CHCl3 + CH3OCH3Chapter - 4 Electrochemistry Class 12 Notes | EduRev

Chapter - 4 Electrochemistry Class 12 Notes | EduRev

Immiscible Liquids:
(i) Ptotal= PA+ PB
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Chapter - 4 Electrochemistry Class 12 Notes | EduRev

Chapter - 4 Electrochemistry Class 12 Notes | EduRev

Chapter - 4 Electrochemistry Class 12 Notes | EduRev
B.P. of solution is less than the individual B.P.’s of both the liquids.

Henry Law :
This law deals with dissolution of gas in liquid i.e. mass of any gas dissolved in any solvent per unit volume is proportional to pressure of gas in equilibrium with liquid,
m α p
m = kρ
Chapter - 4 Electrochemistry Class 12 Notes | EduRev


SOLID STATE

  • Classification of Crystal into Seven System
    Chapter - 4 Electrochemistry Class 12 Notes | EduRev
  • ANALYSIS OF CUBICAL SYSTEM
    Chapter - 4 Electrochemistry Class 12 Notes | EduRev
  • NEIGHBOUR HOOD OF A PARTICLE :
    (i) Simple Cubic (SC) Structure :
    Chapter - 4 Electrochemistry Class 12 Notes | EduRev
    (ii) Body Centered Cubic (BCC) Structure :
    Chapter - 4 Electrochemistry Class 12 Notes | EduRev
    (iii) Face Centered Cubic (FCC) Structure:Chapter - 4 Electrochemistry Class 12 Notes | EduRev
  • DENSITY OF LATTICE MATTER (d) = Chapter - 4 Electrochemistry Class 12 Notes | EduRev
    where NA = Avogadro’s No. M = atomic mass or molecular mass.
  • IONIC CRYSTALS
    Chapter - 4 Electrochemistry Class 12 Notes | EduRev
  • EXAMPLES OF A IONIC CRYSTAL
    (a) Rock Salt (NaCI) Coordination number (6 : 6)
    (b) CsCI C.No. (8 : 8) Edge length of unit cell:- Chapter - 4 Electrochemistry Class 12 Notes | EduRev
    (c) Zinc Blende (ZnS) C.No. (4 : 4) Chapter - 4 Electrochemistry Class 12 Notes | EduRev
    (d) Fluorite structure (CaF2) C.No. (8 : 4) Chapter - 4 Electrochemistry Class 12 Notes | EduRev
  • Crystal Defects (Imperfections)Chapter - 4 Electrochemistry Class 12 Notes | EduRev

CHEMICAL KINETICS & REDIOACTIVITY
RATE/VELOCITY OF CHEMICAL REACTION :

Chapter - 4 Electrochemistry Class 12 Notes | EduRev Mol lit-1 time-1 = mol dm-3 time-1

Types of Rates of chemical reaction :
For a reaction R → P
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Chapter - 4 Electrochemistry Class 12 Notes | EduRev

RATE LAW (DEPENDENCE OF RATE ON CONCENTRATION OF REACTANTS):
Rate = K (conc.)order - differential rate equation or rate expression
Where K = Rate constant = specific reaction rate = rate of reaction when concentration is unity unit of K = (conc)1-order time-1

Order of reaction :
m1A + m2B → products.
R ∝ [A]p [B]q Where p may or may not be equal to m1 & similarly q may or may not be equal to m2.
p is order of reaction with respect to reactant A and q is order of reaction with respect to reactant B and (p + q) is overall order of the reaction.

INTEGRATED RATE LAWS:
C0 or 'a' is initial concentration and Ct or a - x is concentration at time 't'
(a) zero order reactions :
Rate = k [cone.]0 = constant
Rate = k = Chapter - 4 Electrochemistry Class 12 Notes | EduRev or Ct = C0 - kt
Unit of K = mol lit-1 sec-1, Time for completion = C0/k
Chapter - 4 Electrochemistry Class 12 Notes | EduRev Chapter - 4 Electrochemistry Class 12 Notes | EduRev ∴ t1/2 ∝ C0

(b) First Order Reactions :
(i) Let a 1st order reaction is, A → Products
Chapter - 4 Electrochemistry Class 12 Notes | EduRev or Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Chapter - 4 Electrochemistry Class 12 Notes | EduRev Independent of initial concentration.
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Graphical Representation:
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Chapter - 4 Electrochemistry Class 12 Notes | EduRev Chapter - 4 Electrochemistry Class 12 Notes | EduRev

(c) Second order reaction :
2nd order Reactions Two types

Chapter - 4 Electrochemistry Class 12 Notes | EduRev

(d) Psuedo first order reaction :
∴ For A + B → Products [Rate = K [A]1 [B]1]
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Now if ‘B’ is taken in large excess b > > a.
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
∵ ‘b’ is very large can be taken as constant
Chapter - 4 Electrochemistry Class 12 Notes | EduRev ⇒ Chapter - 4 Electrochemistry Class 12 Notes | EduRev k' is psuedo first order rate constant


METHODS TO DETERMINE ORDER OF A REACTION
(a) Initial rate method :
r = k[A]a [B][C]c if Chapter - 4 Electrochemistry Class 12 Notes | EduRev
then for two different initial concentrations of Awe have
Chapter - 4 Electrochemistry Class 12 Notes | EduRev ⇒ Chapter - 4 Electrochemistry Class 12 Notes | EduRev

(b) Using integrated rate law : It is method of trial and error. 

(c) Method of half lives :
for nth order reaction Chapter - 4 Electrochemistry Class 12 Notes | EduRev
(d) Ostwald Isolation Method :
rate = k [A]a [B]b [C]c = k[A]a

METHODS TO MONITOR THE PROGRESS OF THE REACTION :
(a) Progress of gaseous reaction can be monitored by measuring total pressure at a fixed volume & temperature or by measuring total volume of mixture under constant pressure and temperature. Chapter - 4 Electrochemistry Class 12 Notes | EduRev Chapter - 4 Electrochemistry Class 12 Notes | EduRev {Formula is not applicable when n = 1, the value of n can be fractional also.}

(b) By titration method:
1. ∴ a ∝ V0 a - x ∝ VtChapter - 4 Electrochemistry Class 12 Notes | EduRev
2. Study of acid hydrolysis of an easter.
Chapter - 4 Electrochemistry Class 12 Notes | EduRev

(c) By measuring optical roteition produced by the reaction mixture:
Chapter - 4 Electrochemistry Class 12 Notes | EduRev

EFFECT OF TEMPERATURE ON RATE OF REACTION.
Chapter - 4 Electrochemistry Class 12 Notes | EduRev2 to 3 (for most of the reactions)
Arhenius theroy of reaction rate.
Chapter - 4 Electrochemistry Class 12 Notes | EduRev 

Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Arhenius equation
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
If k1 and k2 be the rate constant of a reaction at two different temperature T1 and T2 respectively, then we have
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Chapter - 4 Electrochemistry Class 12 Notes | EduRev Chapter - 4 Electrochemistry Class 12 Notes | EduRev Ea ≥ 0

REVERSIBLE REACTIONS
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
In Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Chapter - 4 Electrochemistry Class 12 Notes | EduRev Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Chapter - 4 Electrochemistry Class 12 Notes | EduRev ⇒ Chapter - 4 Electrochemistry Class 12 Notes | EduRev

(ii) REVERSIBLE 1st ORDER REACATION ( both forward and backward)
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
(iii) SEQUENTIAL 1ST ORDER REACTION
Chapter - 4 Electrochemistry Class 12 Notes | EduRev
Chapter - 4 Electrochemistry Class 12 Notes | EduRev Chapter - 4 Electrochemistry Class 12 Notes | EduRev

CASE-I K1» K
Chapter - 4 Electrochemistry Class 12 Notes | EduRev

CASE-II K2 » K1
Chapter - 4 Electrochemistry Class 12 Notes | EduRev

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