Electrochemistry PYQs

A solution of copper sulphate is electrolysed for 10 minutes with a current of 1.5 amperes. The mass of copper deposited at cathode is: (Given: Molar mass of Cu = 63 g mol⁻¹, 1F = 96487 C mol⁻¹)

Calculate emf of the half cell:

Consider the following compounds: KO₂, H₂O₂ and H₂SO₄. The oxidation states of the underlined elements in them are, respectively,

If the molar conductivity $(\Lambda_m)$ of a $0.050\ \mathrm{mol\ L^{-1}}$ solution of a monobasic weak acid is $90\ \mathrm{S\ cm^2\ mol^{-1}}$, its extent (degree) of dissociation will be [Assume $\Lambda_+^{\circ} = 349.6\ \mathrm{S\ cm^2\ mol^{-1}}$ and $\Lambda_-^{\circ} = 50.4\ \mathrm{S\ cm^2\ mol^{-1}}$.]

Match List I with List II. Choose the correct answer from the options given below:

Mass in grams of copper deposited by passing 9.6487 A current through a voltmeter containing copper sulphate solution for 1000 seconds is: (Given : Molar mass of Cu : 63 g mol⁻¹, 1F = 96487 C)

The conductivity of centimolar solution of KCl at 25°C is 0.0210 ohm⁻¹ cm⁻¹ and resistance of cell containing the solution at 25°C is 60 ohm. The value of cell constant is -

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R : Assertion A : In equation ΔᵣG = −nFEcell, value of ΔᵣG depends on n. Reason R : Ecell is an intensive property and ΔᵣG is an extensive property. In the light of the above statements, choose the correct answer from the options given below:

At 298 K, the standard electrode potentials of Cu²⁺/Cu, Zn²⁺/Zn, Fe²⁺/Fe and Ag⁺/Ag are 0.34 V, −0.76 V, −0.44 V and 0.80 V, respectively. On the basis of standard electrode potential, predict which of the following reaction cannot occur?

Given below are half-cell reactions: Will the permanganate ion, MnO₄⁻, liberate O₂ from water in the presence of an acid?

The molar conductance of NaCl, HCl and CH₃COONa at infinite dilution are 126.45, 426.16 and 91.0 S cm² mol⁻¹ respectively. The molar conductance of CH₃COOH at infinite dilution is:

The molar conductivity of 0.007 M acetic acid is 20 S cm² mol⁻¹. What is the dissociation constant of acetic acid? Choose the correct option.

On electrolysis of dilute sulphuric acid using Platinum (Pt) electrode, the product obtained at anode will be

The number of Faraday's (F) required to produce 20 g of calcium from molten CaCl$_2$ (Atomic mass of Ca = 40 g mol⁻¹) is

Following limiting molar conductivities are given as:

The standard electrode potential ($E^⊖$) values of $\mathrm{Al^{3+}/Al}$, $\mathrm{Ag^+/Ag}$, $\mathrm{K^+/K}$ and $\mathrm{Cr^{3+}/Cr}$ are $-1.66\,V$, $0.80\,V$, $-2.93\,V$ and $-0.74\,V$, respectively. The correct decreasing order of reducing power of the metal is

Name the gas that can readily decolourise acidified $KMnO_4$ solution:

In the electrochemical cell Zn|ZnSO₄(0.01 M)||CuSO₄(1.0 M)|Cu, the emf of this Daniell cell is E₁. When the concentration of ZnSO₄ is changed to 1.0 M and that of CuSO₄ changed to 0.01 M, the emf changes to E₂. From the following, which one is the relationship between E₁ and E₂? (Given, RT/F = 0.059

The molar conductivity of a $0.5\ \text{mol dm}^{-3}$ solution of AgNO₃ with electrolytic conductivity of $5.76 \times 10^{-3}\ \text{S cm}^{-1}$ at $298\ \text{K}$ is:

During the electrolysis of molten sodium chloride, the time required to produce $0.10$ mol of chlorine gas using a current of $3$ amperes is:

The number of electrons delivered at the cathode during electrolysis by a current of $1$ ampere in $60$ seconds is (charge on electron $=1.60\times10^{-19}\ \text{C}$):

Hot concentrated sulphuric acid is a moderately strong oxidizing agent. Which of the following reactions does not show oxidizing behaviour?

Aqueous solution of which of the following compounds is the best conductor of electric current?

Assuming complete ionization, same moles of which of the following compounds will require the least amount of acidified KMnO₄ for complete oxidation?

When 0.1 mol MnO₄²⁻ is oxidised, the quantity of electricity required to completely oxidise MnO₄²⁻ to MnO₄⁻ is:

The weight of silver (at. wt. = 108) displaced by a quantity of electricity which displaces 5600 mL of O₂ at STP will be:

The pair of compounds that can exist together is:

$$(a) H₂O₂ + O₃ → H₂O + 2O₂$$ $$(b) H₂O₂ + Ag₂O → 2Ag + H₂O + O₂$$ Role of hydrogen peroxide in the above reactions is respectively

The reaction of aqueous KMnO₄ with H₂O₂ in acidic conditions gives:

A hydrogen gas electrode is made by dipping platinum wire in a solution of HCl of pH = 10 and by passing hydrogen gas around the platinum wire at one atmosphere pressure. The oxidation potential of the electrode would be

At $25^\circ C$ molar conductance of $0.1$ molar aqueous solution of ammonium hydroxide is $9.54\,ohm^{-1}\,cm^2\,mol^{-1}$ and at infinite dilution its molar conductance is $238\,ohm^{-1}\,cm^2\,mol^{-1}$. The degree of ionisation of ammonium hydroxide at the same concentration and temperature is

A button cell used in watches functions as follows: $$Zn(s)+Ag_2O(s)+H_2O(l) \rightleftharpoons 2Ag(s)+Zn^{2+}(aq)+2OH^{-}(aq)$$ If half-cell potentials are: $$Zn^{2+}(aq)+2e^- \rightarrow Zn(s),\ E^\circ=-0.76V$$ $$Ag_2O(s)+H_2O(l)+2e^- \rightarrow 2Ag(s)+2OH^-(aq),\ E^\circ=0.34V$$ The cell potential will be

The Gibbs energy for the decomposition of Al₂O₃ at 500°C is as follows: $$\frac{2}{3}Al_2O_3 \rightarrow \frac{4}{3}Al + O_2$$ $$\Delta_r G = +960\,kJ\,mol^{-1}$$ The potential difference needed for the electrolytic reduction of aluminium oxide (Al₂O₃) at 500°C is at least:

Molar conductivities (Λₘ°) at infinite dilution of NaCl, HCl and CH₃COONa are 126.4, 425.9 and 91.0 S cm² mol⁻¹ respectively. Λₘ° for CH₃COOH will be :

Standard reduction potentials of the half reactions are given below: $$F_2(g) + 2e^- \rightarrow 2F^-_{(aq)} ; E^0 = +2.85V$$ $$Cl_2(g) + 2e^- \rightarrow 2Cl^-_{(aq)} ; E^0 = +1.36V$$ $$Br_2(l) + 2e^- \rightarrow 2Br^-_{(aq)} ; E^0 = +1.06V$$ $$I_2(s) + 2e^- \rightarrow 2I^-_{(aq)} ; E^0 = +0.53V$$ The strongest oxidizing and reducing agents respectively are:

Four successive members of the first series of the transition metals are listed below. For which one of the standard potential (E°M²⁺⁄M) value has a positive sign?

A solution contains $Fe^{2+}$, $Fe^{3+}$ and $I^-$ ions. This solution was treated with iodine at $35^\circ C$. $E^\circ$ for $Fe^{3+}/Fe^{2+}$ is $+0.77\,V$ and $E^\circ$ for $I_2/2I^-$ = 0.536 V. The favourable redox reaction is:

Which of the following expressions correctly represents the equivalent conductance at infinite dilution of Al₂(SO₄)₃? Given that λ°Al³⁺ and λ°SO₄²⁻ are the equivalent conductances at infinite dilution of the respective ions.

Consider the following relations for emf of an electrochemical cell: (i) EMF of cell = (Oxidation potential of anode) - (Reduction potential of cathode) (ii) EMF of cell = (Oxidation potential of anode) + (Reduction potential of cathode) (iii) EMF of cell = (Reduction potential of anode) + (Reduction potential of cathode) (iv) EMF of cell = (Oxidation potential of anode) - (Oxidation potential of cathode) Which of the above relations are correct

Oxidation number of P in $PO_4^{3-}$, of S in $SO_4^{2-}$ and that of Cr in $Cr_2O_7^{2-}$ are respectively:

Given: (i) $\mathrm{Cu^{2+} + 2e^- \rightarrow Cu},\; E^\circ = 0.337\,V$ (ii) $\mathrm{Cu^{2+} + e^- \rightarrow Cu^+},\; E^\circ = 0.153\,V$ The electrode potential $E^\circ$ for the reaction: $$\mathrm{Cu^+ + e^- \rightarrow Cu}$$ will be:

Among the following which is the strongest oxidizing agent?

$Al_2O_3$ is reduced by electrolysis at low potentials and high currents. If $4.0 \times 10^4$ amperes of current is passed through molten $Al_2O_3$ for $6$ hours, what mass of aluminium is produced? (Assume $100\%$ current efficiency, atomic mass of $Al = 27\,g\,mol^{-1}$)

Kohlrausch's law states that at

Standard free energies of formation (in kJ mol⁻¹) at 298 K are -237.2, -394.4 and -8.2 for H₂O(l), CO₂(g) and pentane(g) respectively. The value of E°cell for the pentane-oxygen cell is

Number of moles of MnO₄⁻ required to oxidize one mole of ferrous oxalate completely in acidic medium will be

Two silver rods are dipped separately in 1 M HCl and 1 M HNO₃. In which of the two acids will the silver rod dissolve under standard conditions

In producing chlorine through electrolysis, 100 W power at 125 V is being consumed. How much chlorine per minute is liberated? ECE of chlorine is 0.367 × 10⁻⁶ kg/ C:

If E°Fe²⁺/Fe = -0.441 V and E°Fe³⁺/Fe²⁺ = 0.771 V, the standard emf of the reaction Fe + 2Fe³⁺ → 3Fe²⁺ will be:

A hypothetical electrochemical cell is shown below: A|A⁺(xM)||B⁺(yM)|B The emf measured is +0.20 V. The cell reaction is:

$4.5\ g$ of aluminium $(atomic\ mass=27)$ is deposited at cathode from $Al^{3+}$ solution by a certain quantity of electric charge. The volume of hydrogen produced at STP from $H^+$ ions in solution by the same quantity of electric charge will be: