Electrochemistry

Variation of Conductivity with Concentration and Measurement

The molar conductivity of a strong electrolyte at infinite dilution is 240 S cm² mol⁻¹. If its molar conductivity at 0.0

For a strong electrolyte, α = (Lambdam/Lambdam°) , but here it’s less than 1 due to ion interaction. α = (228/240) = 0.95 .

Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Variation of Conductivity with Concentration and Measurement

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Variation of Conductivity with Concentration and Measurement

What is the emf of a cell Zn(s) | Zn²⁺(0.001 M) || H⁺(1 M) | H₂(g)(1 bar) | Pt(s) at 298 K? (Given: E°Zn²⁺/Zn = -0.76 V

E°cell = 0.00 - (-0.76) = 0.76 V . Ecell = 0.76 - (0.059/2) log (0.001/1²) = 0.76 + 0.0885 = 0.8485 V .

Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Variation of Conductivity with Concentration and Measurement

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Variation of Conductivity with Concentration and Measurement

A cell operates with Ecell = 1.50 V at 298 K when [Anode] = 0.001 M and [Cathode] = 0.1 M . If E°cell = 1.44 V , what is

Ecell = E°cell - (0.059/n) log Q , 1.50 = 1.44 - (0.059/2) log Q . 0.06 = -0.0295 log Q , log Q = -(0.06/0.0295) = -2.034, Q = 10⁻².⁰³⁴ ≈ 0.0092 . Since Q = ([Anode]/[Cathode]) = (0.001/0.1) = 0.01 , matches approximately.

Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Variation of Conductivity with Concentration and Measurement

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Variation of Conductivity with Concentration and Measurement

In a fuel cell, what is the cathode reaction?

Cathode: O₂ + 4H⁺ + 4e⁻ → 2H₂O .

Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Variation of Conductivity with Concentration and Measurement

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Variation of Conductivity with Concentration and Measurement

What is the equilibrium constant for a cell reaction with E°cell = 0.236 V at 298 K involving 2 electrons?

E°cell = (0.059/n) log Kc . 0.236 = (0.059/2) log Kc , log Kc = 8, Kc = 10⁸ .

Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Variation of Conductivity with Concentration and Measurement

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Variation of Conductivity with Concentration and Measurement

The conductivity of a 0.01 M LiNO₃ solution is 0.00135 S cm⁻¹. What is the molar conductivity?

Lambdam = (kappa × 1000/c) = (0.00135 × 1000/0.01) = 135 S cm² mol⁻¹ .

Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Variation of Conductivity with Concentration and Measurement

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Variation of Conductivity with Concentration and Measurement

The molar conductivity of NH₄Cl at infinite dilution is 149.7 S cm² mol⁻¹. If λ°NH_₄⁺ = 73.4 S cm² mol⁻¹ , what is λ°Cl⁻

Lambdam° = λ°NH_₄⁺ + λ°Cl⁻ . 149.7 = 73.4 + λ°Cl⁻ , λ°Cl⁻ = 76.3 S cm² mol⁻¹ .

Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Variation of Conductivity with Concentration and Measurement

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Variation of Conductivity with Concentration and Measurement

A cell reaction has E°cell = 0.74 V and Δr G° = -142610 J/mol at 298 K. How many electrons are transferred? (F = 96500 C

Δr G° = -n F E°cell , -142610 = -n × 96500 × 0.74 . n = (142610/96500 × 0.74) = (142610/71410) ≈ 2 .

Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Variation of Conductivity with Concentration and Measurement

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Variation of Conductivity with Concentration and Measurement

What is the emf of the cell Co(s) | Co²⁺(0.01 M) || Ag⁺(0.001 M) | Ag(s) at 298 K? (Given: E°Co²⁺/Co = -0.28 V , E°Ag⁺/A

E°cell = 0.80 - (-0.28) = 1.08 V . Ecell = 1.08 - (0.059/2) log ([Co²⁺]/[Ag⁺]²) = 1.08 - 0.0295 log (0.01/0.000001) = 1.08 - 0.177 = 0.903 V .

Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Variation of Conductivity with Concentration and Measurement

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Variation of Conductivity with Concentration and Measurement

A hydrogen electrode operates at 298 K with PH_₂ = 0.5 atm and pH = 3. What is its potential? (Given: E°H⁺/H_₂ = 0.00 V

E = E° - (0.059/2) log (PH_₂/[H⁺]²) , [H⁺] = 10⁻³ . E = 0 - 0.0295 log (0.5/10⁻⁶) = 0 - 0.0295 × 5.301 = -0.1564 V .

Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Variation of Conductivity with Concentration and Measurement

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Variation of Conductivity with Concentration and Measurement

What is the emf of a cell Ni(s) | Ni²⁺(0.1 M) || Cu²⁺(0.001 M) | Cu(s) at 298 K? (Given: E°Ni²⁺/Ni = -0.25 V , E°Cu²⁺/Cu

E°cell = 0.34 - (-0.25) = 0.59 V . Ecell = 0.59 - (0.059/2) log (0.1/0.001) = 0.59 - 0.059 = 0.531 V .

Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Variation of Conductivity with Concentration and Measurement

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Variation of Conductivity with Concentration and Measurement

A cell has E°cell = 0.59 V and an equilibrium constant of 10²⁰ at 298 K. How many electrons are transferred?

E°cell = (0.059/n) log Kc , 0.59 = (0.059/n) × 20 , n = (1.18/0.59) = 2 .

Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Variation of Conductivity with Concentration and Measurement

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