Electrochemistry
Electrochemistry Lecture-1
Conductance of electrolytic solutions
Good conductor - Almost fully conducting
Semi conductor - Partially conducting
Insulators - Not conducting
Conductance of electrolytic solutions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → ( κ ) (\kappa) ( κ ) → \rightarrow → → \rightarrow → → \rightarrow → λ m v s C for weak electrolyte \lambda_m vs \sqrt {C}\text{for weak electrolyte} λ m v s C for weak electrolyte → \rightarrow → → \rightarrow → λ o ( S c m m o l − 1 ) for different ions \lambda^o (S cm mol^{-1})\text {for different ions} λ o ( S c mm o l − 1 ) for different ions
Electrochemistry Lecture-1
Difference between metallic conductor & electrolytic conductor
Metallic Conductor Electrolytic Conductor
1. Electrons
1. Ions
2. No transport of matter
2. Electrolyte / ions are transpotive
3. R ∝ T R\propto T R ∝ T
R ∝ 1 T R\propto \frac{1}{T} R ∝ T 1
4. No chemical change
4. Chemical Change at the electrodes
Conductance of electrolytic solutions → \rightarrow → Difference between metallic conductor & electrolytic conductor → \rightarrow → → \rightarrow → → \rightarrow → ( κ ) (\kappa) ( κ ) → \rightarrow → → \rightarrow → → \rightarrow → λ m v s C for weak electrolyte \lambda_m vs \sqrt {C}\text{for weak electrolyte} λ m v s C for weak electrolyte → \rightarrow → → \rightarrow → λ o ( S c m m o l − 1 ) for different ions \lambda^o (S cm mol^{-1})\text {for different ions} λ o ( S c mm o l − 1 ) for different ions
Electrochemistry Lecture-1
Some important points
Resistance (R)
R ∝ l R \propto l R ∝ l
R ∝ 1 A R \propto \frac{1}{A} R ∝ A 1
R ∝ l A R \propto \frac{l}{A} R ∝ A l
or R = ρ l A R = \rho \frac{l}{A} R = ρ A l
Conductance of electrolytic solutions → \rightarrow → → \rightarrow → Some important points → \rightarrow → → \rightarrow → ( κ ) (\kappa) ( κ ) → \rightarrow → → \rightarrow → → \rightarrow → λ m v s C for weak electrolyte \lambda_m vs \sqrt {C}\text{for weak electrolyte} λ m v s C for weak electrolyte → \rightarrow → → \rightarrow → λ o ( S c m m o l − 1 ) for different ions \lambda^o (S cm mol^{-1})\text {for different ions} λ o ( S c mm o l − 1 ) for different ions
Electrochemistry Lecture-1
Some important points
ρ → specific resistance \rho \rightarrow \text{specific resistance} ρ → specific resistance
Conductance = 1 R = \frac{1}{R} = R 1
Conductance = 1 ρ ⋅ A l = \frac{1}{\rho} \cdot \frac{A}{l} = ρ 1 ⋅ l A
Unit of resistance O h m Ohm O hm
Unit of conductance O h m − 1 Ohm^{-1} O h m − 1
1 ρ → specific conductance or conductivity \frac{1}{\rho} \rightarrow \text{specific conductance or conductivity} ρ 1 → specific conductance or conductivity
Conductance of electrolytic solutions → \rightarrow → → \rightarrow → Some important points → \rightarrow → → \rightarrow → ( κ ) (\kappa) ( κ ) → \rightarrow → → \rightarrow → → \rightarrow → λ m v s C for weak electrolyte \lambda_m vs \sqrt {C}\text{for weak electrolyte} λ m v s C for weak electrolyte → \rightarrow → → \rightarrow → λ o ( S c m m o l − 1 ) for different ions \lambda^o (S cm mol^{-1})\text {for different ions} λ o ( S c mm o l − 1 ) for different ions
Electrochemistry Lecture-1
Some important terms
Conductance = specific conductance × A l \text{Conductance} = \text{specific conductance} \times \frac{A}{l} Conductance = specific conductance × l A
⇒ Specific Conductance = Conductance × l A \Rightarrow \text{Specific Conductance} = \text{Conductance} \times \frac{l}{A} ⇒ Specific Conductance = Conductance × A l
l A → cell constant \frac{l}{A} \rightarrow \text{cell constant} A l → cell constant
Specific conductance = conductance × cell constant \text{Specific conductance} = \text{conductance} \times \text{cell constant} Specific conductance = conductance × cell constant
Conductance of electrolytic solutions → \rightarrow → → \rightarrow → → \rightarrow → Some important terms → \rightarrow → ( κ ) (\kappa) ( κ ) → \rightarrow → → \rightarrow → → \rightarrow → λ m v s C for weak electrolyte \lambda_m vs \sqrt {C}\text{for weak electrolyte} λ m v s C for weak electrolyte → \rightarrow → → \rightarrow → λ o ( S c m m o l − 1 ) for different ions \lambda^o (S cm mol^{-1})\text {for different ions} λ o ( S c mm o l − 1 ) for different ions
Electrochemistry Lecture-1
Some important terms
Unit of Specific conductance= Siemens × l A \times \frac{l}{A} × A l = S m − 1 = S m^{-1} = S m − 1
For unknown resistance Wheatstone bridge principal is used
R 1 R 2 = R 3 R 4 \frac{R_1}{R_2} = \frac{R_3}{R_4} R 2 R 1 = R 4 R 3
R 1 = R 3 R 4 ⋅ R 2 ( Balance point ) R_1 = \frac{R_3}{R_4} \cdot R_2 (\text{Balance point}) R 1 = R 4 R 3 ⋅ R 2 ( Balance point )
Conductance of electrolytic solutions → \rightarrow → → \rightarrow → → \rightarrow → Some important terms → \rightarrow → ( κ ) (\kappa) ( κ ) → \rightarrow → → \rightarrow → → \rightarrow → λ m v s C for weak electrolyte \lambda_m vs \sqrt {C}\text{for weak electrolyte} λ m v s C for weak electrolyte → \rightarrow → → \rightarrow → λ o ( S c m m o l − 1 ) for different ions \lambda^o (S cm mol^{-1})\text {for different ions} λ o ( S c mm o l − 1 ) for different ions
Electrochemistry Lecture-1
Specific conductance or conductivity( κ ) (\kappa) ( κ )
Specific Conductance = Conductance × \times ×
Materials
Conductivity (S/m)
C u \mathrm{Cu} Cu 6 × 10 3 6 \times 10^3 6 × 1 0 3
Silver
6.2 × 10 3 6.2 \times 10^3 6.2 × 1 0 3
Glass
∼ 1 × 10 − 16 \sim 1 \times 10^{-16} ∼ 1 × 1 0 − 16
Pure Water
∼ 4 × 10 − 5 ( H 2 O ⇌ H + + O H H − ) \sim 4 \times 10^{-5}\left(\mathrm{H}_2 \mathrm{O} \rightleftharpoons \mathrm{H}^{+}+\mathrm{OH} \mathrm{H}^{-}\right) ∼ 4 × 1 0 − 5 ( H 2 O ⇌ H + + OH H − )
0.1 M H c l 0.1 \mathrm{M} \mathrm{Hcl} 0.1 M Hcl ∼ 4 − > H + , C l − \sim 4->\mathrm{H}^{+}, \mathrm{Cl}^{-} ∼ 4 − > H + , Cl −
G e \mathrm{Ge} Ge ∼ 2 \sim 2 ∼ 2
Conductance of electrolytic solutions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → Specific conductance or conductivity( κ ) (\kappa) ( κ ) → \rightarrow → → \rightarrow → → \rightarrow → λ m v s C for weak electrolyte \lambda_m vs \sqrt {C}\text{for weak electrolyte} λ m v s C for weak electrolyte → \rightarrow → → \rightarrow → λ o ( S c m m o l − 1 ) for different ions \lambda^o (S cm mol^{-1})\text {for different ions} λ o ( S c mm o l − 1 ) for different ions
Electrochemistry Lecture-1
Molar conductance
Molar Conductance (λ m \lambda_{m} λ m
λ m = κ c \lambda_m = \frac{\kappa}{c} λ m = c κ
κ → S m − 1 \kappa \rarr Sm^{-1} κ → S m − 1 \qquad
C = m o l C = mol C = m o l m − 3 m^{-3} m − 3
λ m → S m 2 m o l − 1 \lambda_m \rightarrow Sm^2 mol^{-1} λ m → S m 2 m o l − 1
Conductance of electrolytic solutions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → ( κ ) (\kappa) ( κ ) → \rightarrow → Molar conductance → \rightarrow → → \rightarrow → λ m v s C for weak electrolyte \lambda_m vs \sqrt {C}\text{for weak electrolyte} λ m v s C for weak electrolyte → \rightarrow → → \rightarrow → λ o ( S c m m o l − 1 ) for different ions \lambda^o (S cm mol^{-1})\text {for different ions} λ o ( S c mm o l − 1 ) for different ions
Electrochemistry Lecture-1
Molar conductance
No. of ions
Charge of the ions M ( 1 ) + , M ( 2 ) 2 + , M ( 3 ) 3 + M_{(1)}^{+}, M_{(2)}^{2+}, M_{(3)}^{3+} M ( 1 ) + , M ( 2 ) 2 + , M ( 3 ) 3 +
Speed of ions
Conductance of electrolytic solutions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → ( κ ) (\kappa) ( κ ) → \rightarrow → Molar conductance → \rightarrow → → \rightarrow → λ m v s C for weak electrolyte \lambda_m vs \sqrt {C}\text{for weak electrolyte} λ m v s C for weak electrolyte → \rightarrow → → \rightarrow → λ o ( S c m m o l − 1 ) for different ions \lambda^o (S cm mol^{-1})\text {for different ions} λ o ( S c mm o l − 1 ) for different ions
Electrochemistry Lecture-1
Important terms
1M NaCl diluted into 10 − 2 10^{-2} 1 0 − 2 1 2 10 − 2 M \frac{1}{2}10^{-2}M 2 1 1 0 − 2 M
Specific conductance × \times ×
No. of ions ↓ \downarrow ↓
Charge on ion → \rightarrow →
Speed of ions → \rightarrow →
Conductance of electrolytic solutions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → ( κ ) (\kappa) ( κ ) → \rightarrow → → \rightarrow → Important terms → \rightarrow → λ m v s C for weak electrolyte \lambda_m vs \sqrt {C}\text{for weak electrolyte} λ m v s C for weak electrolyte → \rightarrow → → \rightarrow → λ o ( S c m m o l − 1 ) for different ions \lambda^o (S cm mol^{-1})\text {for different ions} λ o ( S c mm o l − 1 ) for different ions
Electrochemistry Lecture-1
Important terms
Molar Conductance ( λ m ) = κ C (\lambda_m)= \frac{\kappa}{C} ( λ m ) = C κ
Unit of C(mol / m 3)
As length(l) = 1, so V = A × l = A A\times l = A A × l = A
λ m = κ A l ⇒ λ m \lambda_m = \kappa \frac{A}{l}\Rightarrow \lambda_m λ m = κ l A ⇒ λ m κ × V \kappa\times{V} κ × V
κ \kappa κ
V increases on dilution
λ m \lambda_m λ m
Conductance of electrolytic solutions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → ( κ ) (\kappa) ( κ ) → \rightarrow → → \rightarrow → Important terms → \rightarrow → λ m v s C for weak electrolyte \lambda_m vs \sqrt {C}\text{for weak electrolyte} λ m v s C for weak electrolyte → \rightarrow → → \rightarrow → λ o ( S c m m o l − 1 ) for different ions \lambda^o (S cm mol^{-1})\text {for different ions} λ o ( S c mm o l − 1 ) for different ions
Electrochemistry Lecture-1
λ m v s C for weak electrolyte \lambda_m vs \sqrt {C}\text{for weak electrolyte} λ m v s C for weak electrolyte
C H 3 C O O H → Weak electrolyte
C H 3 C O O H ( 1 − α ) ⇌ H + α + C H 3 C O O − α \underset{\substack{\mathrm{(1-\alpha)}}}{\mathrm{CH}_3 \mathrm{COOH}} \rightleftharpoons
\underset{\alpha}{\mathrm{H}^{+}}+\underset{\alpha}{\mathrm{CH}_3 \mathrm{COO}^{-}} ( 1 − α ) CH 3 COOH ⇌ α H + + α CH 3 COO −
λ m = K V
λ m = λ m 0 + A C
λ m o → \lambda_m^{o} \rightarrow λ m o →
Conductance of electrolytic solutions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → ( κ ) (\kappa) ( κ ) → \rightarrow → → \rightarrow → → \rightarrow → λ m v s C for weak electrolyte \lambda_m vs \sqrt {C}\text{for weak electrolyte} λ m v s C for weak electrolyte → \rightarrow → → \rightarrow → λ o ( S c m m o l − 1 ) for different ions \lambda^o (S cm mol^{-1})\text {for different ions} λ o ( S c mm o l − 1 ) for different ions
Electrochemistry Lecture-1
Köhlrausch law of independent migration of ions
Λ m o ( K C l ) − Λ m o ( N a C l ) \Lambda_m^{o}(KCl) - \Lambda_m^{o} (NaCl) Λ m o ( K Cl ) − Λ m o ( N a Cl )
= Λ m ∘ ( K B r ) − Λ m ∘ ( N a B r ) =\Lambda_m^{\circ}(K{Br})-\Lambda_m^{\circ}\left(Na{Br}\right) = Λ m ∘ ( K B r ) − Λ m ∘ ( N a B r )
= λ m 0 ( K I ) =\lambda^0_m(KI) = λ m 0 ( K I ) λ m 0 ( N a I ) \lambda^0_m(NaI) λ m 0 ( N a I ) ∼ 23 S c m 2 m o l − 1 \sim 23 \mathrm{Scm}^2 \mathrm{~mol}^{-1} ∼ 23 Scm 2 mol − 1
λ m 0 ( N a B r ) \lambda^0_m(NaBr) λ m 0 ( N a B r ) λ m 0 ( N a C l ) \lambda^0_m(NaCl) λ m 0 ( N a Cl ) λ m 0 ( K B r ) \lambda^0_m(KBr) λ m 0 ( K B r ) λ m 0 ( K C l ) \lambda^0_m(KCl) λ m 0 ( K Cl ) ∼ 23 S c m 2 m o l − 1 \sim 23 \mathrm{Scm}^2 \mathrm{~mol}^{-1} ∼ 23 Scm 2 mol − 1
λ m 0 ( K C l ) \lambda^0_m(KCl) λ m 0 ( K Cl ) λ m 0 ( K + ) \lambda^0_m(K^+) λ m 0 ( K + ) λ m 0 ( C l − ) \lambda^0_m(Cl^-) λ m 0 ( C l − )
Conductance of electrolytic solutions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → ( κ ) (\kappa) ( κ ) → \rightarrow → → \rightarrow → → \rightarrow → λ m v s C for weak electrolyte \lambda_m vs \sqrt {C}\text{for weak electrolyte} λ m v s C for weak electrolyte → \rightarrow → Köhlrausch law of independent migration of ions → \rightarrow → λ o ( S c m m o l − 1 ) for different ions \lambda^o (S cm mol^{-1})\text {for different ions} λ o ( S c mm o l − 1 ) for different ions
Electrochemistry Lecture-1
λ o ( S c m m o l − 1 ) for different ions \lambda^o (S cm mol^{-1})\text {for different ions} λ o ( S c mm o l − 1 ) for different ions
λ o \lambda^o λ o m o l − 1 mol^{-1} m o l − 1
H + − 349.6 H^+-349.6 H + − 349.6
O H − − 199.1 OH^- {-} 199.1 O H − − 199.1
K + − 73.5 K^+-73.5 K + − 73.5
C l − − 76.3 Cl^- {-}76.3 C l − − 76.3
λ m 0 \lambda^0_m λ m 0
Conductance of electrolytic solutions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → ( κ ) (\kappa) ( κ ) → \rightarrow → → \rightarrow → → \rightarrow → λ m v s C for weak electrolyte \lambda_m vs \sqrt {C}\text{for weak electrolyte} λ m v s C for weak electrolyte → \rightarrow → → \rightarrow → λ o ( S c m m o l − 1 ) for different ions \lambda^o (S cm mol^{-1})\text {for different ions} λ o ( S c mm o l − 1 ) for different ions
