AIIMS Chemistry Electrochemistry Class 12 Questions

Calculate emf of cell at 25°C

$\text{Cell notation : } \text{M} \mid \text{M}^{2+}_{0.01} \parallel \text{M}^{2+}_{0.0001} \mid \text{M}$

If value of $E^\circ_{\text{Cell}}$ is 4 volt (Given $\frac{RT}{F} \ln 10 = 0.06$)

The conductivity of a 0.05 M solution of a weak monobasic acid is 10⁻³ S cm⁻¹. If λᵐ∞ for weak acid is 500 S cm² mol⁻¹, calculate Kₐ of weak monobasic acid:

The decomposition of $\text{NH}_3$ on Pt surface is a zero order reaction. If the value of rate constant is $2 \times 10^{-4} \text{ mole liter}^{-1} \text{ sec}^{-1}$. The rate of appearance of $\text{N}_2$ and $\text{H}_2$ are respectively.

Assertion: One mole of silver deposits by 1 Faraday charge. Reason: Faraday charge required depends upon no of electron.

Assertion : Mg cannot be obtained by reduction of its metal oxide by aluminium. Reason : Mg is less electropositive than Al.

In following cell reaction Mg(s) + 2Ag⁺ (0.001M) → Mg²⁺ (0.20M) + 2Ag(s) Calculate E₀cell for the reaction [E° = 3.17 V, $\frac{2.30RT}{F}$ = 0.054]

Time taken to completely (in hr) decompose 36 g water by passing 3A current is:

Cell equation:

A + 2B²⁺ → A²⁺ + 2B

A²⁺ + 2e⁻ → A E°=+0.34 V

And log₁₀K=15.6 at 300 K for cell reactions. Find E° for B⁺ + e⁻ → B. Given $\left[\frac{2.303RT}{F} = 0.059\right]$ at $300\text{ K}$

Which of the following is true for $\text{N}_2\text{O}_5$?

Which of the following can be reduced easily?

Assertion : $\text{NaCl}_{\text{(aq)}}$ electrolysis produces $\text{Na}$ metal.

Reason : $\text{Na}^+$ is obtained at cathode.

$0.1\text{ mole, per litre}$ solution present in conductivity cell where electrode of $100\text{ cm}^2$ area placed at $1\text{ cm}$ and resistance observe is $5 \times 10^3\text{ Ohm}$, what is molar conductivity of solution?

The dielectric constant of $\text{H}_2\text{O}$ is 80. The electrostatic force of attraction between $\text{Na}^+$ and $\text{Cl}^-$ will be

For hydrogen-oxygen fuel cell, the cell reaction is

$2\text{H}_2(\text{g}) + \text{O}_2(\text{g}) \rightarrow 2\text{H}_2\text{O}(\text{l})$

If $\Delta G_f^\circ(\text{H}_2\text{O}) = -237.2 \text{ kJmol}^{-1}$, then emf of this cell is

The standard EMF for the cell reaction, Zn + Cu²⁺ → Cu + Zn²⁺ is 1.1 volt at 25°C. The EMF for the cell reaction, when 0.1 M Cu²⁺ and 0.1M Zn²⁺ solutions are used, at 25°C is

Assertion : Reverse current flows in charging of lead storage battery:

Reason : During charging 4 PbO PbSO convert into Pb and 2

Assertion : $\text{KCl/NaCl/NH}_4\text{Cl}$ etc. cannot be used in the salt bridge of a cell containing silver.

Reason : A salt bridge contains concentrated solution of an inert electrolyte like $\text{KCl}$, $\text{KNO}_3$, $\text{NH}_4\text{NO}_3$ etc. or solidified solution of such an electrolyte in agar-agar and gelatine.

Assertion (A): At the end of electrolysis using platinum electrodes, an aqueous solution of $\text{CuSO}_4$ turns colourless.

Reason (R): During the electrolysis $\text{CuSO}_4$ changes to $\text{Cu(OH)}_2$ during electrolysis.

The number of coulombs required to reduce 12.3 g of nitrobenzene to aniline is

Assertion (A): $E_{\text{cell}}$ increases with increase in concentration of $\text{Ag}^+$ ions.

Reason (R): $E_{\text{cell}}$ has positive value.

How many Faradays of electricity are required for the given reaction to occur? MnO₄⁻ → Mn²⁺

A conductivity cell has a cell constant of 0.5 cm⁻¹. This cell when filled with 0.01 M NaCl solution has a resistance of 384 Ω at 25°C. Calculate the equivalent conductance of the given solution.

Assertion: In electrolysis, the quantity of electricity needed for depositing 1 mole silver is different from that required for 1 mole of copper. Reason: The molecular weights of silver and copper are different.

Calculate the emf of the cell in which of the following reaction takes place Ni(s) + 2Ag⁺(0.002M) → Ni²⁺(0.160M) + 2Ag(s) (Give that E°cell = 1.05V)

Salts of metals X, Y and Z are electrolysed under identical condition using same quantity of electricity. It was observed that 4.2 g of X, 5.4 g of Y and 19.2 g of Z were deposited at respective cathode. If the atomic weights of X, Y, Z are 7, 27 and 64 respectively, then their ratio of valencies is

Assertion (A) Iron is protected from corrosion by connecting magnesium metal with it.

Reason (R) Iron acts as cathode and magnesium as anode which gradually disappears.

An increase in equivalence conductance of a strong electrolyte with dilution is mainly due to

Assertion Electrolysis of molten CaH2 produces hydrogen gas at anode. Reason In CaH2, hydrogen is present in the form of hydride H−.

Electrode potential of hydrogen electrode is 18 mV, then [H⁺] is

Assertion: Cu is stronger reducing agent than H₂. Reason: E° of Cu²⁺/Cu is negative.

For Zn²⁺ | Zn, E° = -0.76 V then EMF of the cell Zn/Zn²⁺(1M)|2H⁺(1M)|H₂(1 atm) will be

Assertion : Sodium acetate on Kolbe’s electrolysis gives methane. Reason : Methyl free radical is formed at cathode.

Assertion : Reduction potential of Mn (+3 to +2) is more positive than Fe (+3 to +2). Reason : Ionisation potential of Mn is more than that of Fe.

Assertion : A reaction is spontaneous if E_cell = +ve. Reason : For E_cell = +ve, ΔG is always –ve.

A factory produces 40 kg of calcium in two hours by electrolysis. How much aluminium can be produced by same current in 2 hours if current efficiency is 50%?

Calculate Λ°m using appropriate molar conductances of the electrolytes listed above at infinite dilution in H₂O at 25°C.

The standard half-cell reduction potential for Ag⁺|Ag is 0.7991 V at 25°C. Given the experimental value Ksp = 1.56×10⁻¹⁰ for AgCl, calculate the standard half-cell reduction potential for the Ag|AgCl electrode.

For the electrochemical cell, M | M⁺ || X⁻ | X, E°(M⁺/M) = 0.44 V and E°(X/X⁻) = 0.33 V. From this data one can deduce that

Assertion: Zinc displaces copper from copper sulphate solution. Reason: The E° of zinc i$s^{-0}$.76 V and that of copper is +0.34 V.

The specific conductance of a N/10 KCl at 25°C is 0.0112 Ω⁻¹ cm⁻¹. The resistance of cell containing solution at the same temperature was found to be 55 Ω. The cell constant will be

Which of the following has the highest tendency to give the reaction, Mⁿ⁺ (aq) + e⁻ → Mⁿ⁺⁻¹ (aq) ?

Hydrofluoric acid is a weak acid. At 25°C, the molar conductivity of a 0.002 M HF is 176.2 Ω⁻¹ cm² mol⁻¹. If its Λ₀ = 405.2 Ω⁻¹ cm² mol⁻¹. Equilibrium constant at the given concentration is

The time period to coat a metal surface of 80 cm² with 5 × 10⁻³ cm thick layer of silver (density 1.05 g cm⁻³) with the passage of 3 Å current through a silver nitrate solution is

For the following concentration cell, to be spontaneous Pt(H₂)|P₁ atm. ||Pt|Cl⁻|P₂ atm. Which of the following is correct?

EMF of the cell reaction is Zn + Fe²⁺ → Zn²⁺ + Fe

To observe the effect of concentration on the conductivity electrolytes of different nature were taken in two vessels A and B. A contains weak electrolyte NH₄OH and B contains strong electrolyte NaCl. In both containers, concentration of respective electrolyte was increased and conductivity observed.

Assertion: Copper metal gets readily corroded in acidic aqueous solution. Reason: Free energy change for this process is negative.

Faraday law of electrolysis indirectly shows

Assertion : Copper sulphate solution is not stored in zinc vessel.

Reason : Zinc forms complex with CuSO₄.

The charge required for the reduction of 1 mol of MnO₄⁻ to MnO₂ is