Solution of Chapter 3. Electrochemistry (Chemistry Part-I Book)

How would you determine the standard electrode potential of the system Mg²⁺|Mg?

Can you store copper sulphate solutions in a zinc pot?

Consult the table of standard electrode potentials and suggest three substances that can oxidise ferrous ions under suitable conditions

Calculate the potential of hydrogen electrode in contact with a solution whose pH is 10.

Calculate the emf of the cell in which the following reaction takes place:

Ni(S) + 2Ag⁺ (0.002M) → Ni²⁺ (0.160 M) + 2Ag(s)

The Cell in which the following reaction occurs:

2Fe³⁺(aq) + 2I^– (aq) → 2Fe²⁺(aq) + I₂(s) has E⁰_cell = 0.236V at 298 K.

Calculate the standard Gibbs energy and the equilibrium constant of the cell reaction.

Why does the conductivity of a solution decrease with dilution?

Suggest a way to determine the Λ°_m value of water

The molar conductivity of 0.025 mol L^–1 methanoic acid is 46.1 S cm² mol^–1. Calculate its degree of dissociation and dissociation constant. Given λ⁰_(H+) = 349.6 S cm² mol^–1 and λ⁰ (HCOO^–) = 54.6 S cm² mol^–1.

If a current of 0.5 ampere flows through a metallic wire for 2 hours, then how many electrons would flow through the wire?

Suggest a list of metals that are extracted electrolytically.

Consider the reaction: Cr₂O₇^2– + 14H⁺ + 6e^–⇒ 2Cr³⁺ + 7H₂O. What is the quantity of electricity in coulombs needed to reduce 1 mol of Cr₂O₇^2–?

Write the chemistry of recharging the lead storage battery, highlighting all the materials that are involved during recharging

Suggest two materials other than hydrogen that can be used as fuels in fuel cells.

Explain how rusting of iron is envisaged as setting up of an electrochemical cell.

Arrange the following metals in the order in which they displace each other from the solution of their salts.

Al, Cu, Fe, Mg, and Zn.

Given the standard electrode potentials,

K⁺ /K = –2.93V, Ag⁺ /Ag = 0.80V,

Hg²⁺ /Hg = 0.79V

Mg²⁺ /Mg = –2.37 V, Cr³⁺ /Cr = – 0.74V

Arrange these metals in their increasing order of reducing power.

Depict the galvanic cell in which the reaction

Zn(s) + 2Ag⁺ (aq) → Zn²⁺ (aq) + 2Ag(s) takes place. Further show:

1) Which of the electrode is negatively charged?

2) The carriers of the current in the cell.

3) Individual reaction at each electrode.

Calculate the standard cell potentials of galvanic cell in which the following reactions take place:

(i) 2Cr(s) + 3Cd²⁺ (aq) → 2Cr³⁺ (aq) + 3Cd

(ii) Fe² + (aq) + Ag⁺ (aq) → Fe³⁺ (aq) + Ag(s)

Calculate the Δ_rG⁰ and equilibrium constant(K) of the reactions.

Write the Nernst equation and emf of the following cells at 298 K:

(i) Mg(s)|Mg²⁺ (0.001M)||Cu²⁺ (0.0001 M)|Cu(s)

(ii) Fe(s)|Fe²⁺ (0.001M)||H⁺ (1M)|H₂(g)(1bar)| Pt(s)

(iii) Sn(s)|Sn²⁺ (0.050 M)||H⁺ (0.020 M)|H₂(g) (1 bar)|Pt(s)

(iv) Pt(s)|Br₂(l)|Br^–(0.010 M)||H⁺ (0.030 M)| H₂(g) (1 bar)|Pt(s).

In the button cells widely used in watches and other devices the following reaction takes place:

Zn_(s) + Ag₂O_(s) + H₂O_(l)→ Zn²⁺ _(aq) + 2Ag_(s) + 2OH^–(aq). Determine Δ_rG⁰ and E⁰ for the reaction.

Define conductivity and molar conductivity of the solution of an electrolyte. Discuss their variation with concentration.

The conductivity of 0.20 M solution of KCl at 298 K is 0.0248 S cm^–1. Calculate its molar conductivity.

The resistance of a conductivity cell containing 0.001M KCl solution at 298 K is 1500 Ω. What is the cell constant if the conductivity of 0.001M KCl solution at 298 K is 0.146 × 10^–3 S cm^–1.

The conductivity of sodium chloride at 298 K has been determined at different concentrations and the results are given below:

Calculate Λ_m for all concentrations and draw a plot between Λ_m and c^1/2. Find the value of Λ⁰_m.

Conductivity of 0.00241 M acetic acid is 7.896 × 10^–5 S cm^–1. Calculate its molar conductivity. If ∧⁰_m for acetic acid is 390.5 S cm²mol^–1, what is its dissociation constant?

How much charge is required for the following reductions:

(i) 1 mol of Al^{3 +} to Al?

(ii) 1 mol of Cu^{2 +} to Cu?

(iii) 1 mol of MnO^–₄ to Mn²⁺ ?

How much electricity in terms of Faraday is required to produce

(i) 20.0 g of Ca from molten CaCl₂?

(ii) 40.0 g of Al from molten Al₂O₃?

How much electricity is required in coulomb for the oxidation of

(i) 1 mol of H₂O to O₂?

(ii) 1 mol of FeO to Fe₂O₃?

A solution of Ni(NO₃)₂ is electrolysed between platinum electrodes using a current of 5 amperes for 20 minutes. What is mass of Ni deposited at the cathode?

Given -

Current = 5A

Time - 20 minutes

Mass of Ni deposited = ?

Three electrolytic cells A,B,C containing solutions of ZnSO₄, AgNO₃ and CuSO₄, respectively are connected in series. A steady current of 1.5 amperes was passed through them until 1.45 g of silver deposited at the cathode of cell B. How long did the current flow? What mass of copper and zinc were deposited?

Given -

I = 1.5 A

W = 1.45 g of Ag

t = ?

n = 1

Using the standard electrode potentials given in Table 3.1, predict if the reaction between the following is feasible:

(i) Fe^{3 +} (aq) and I^–(aq)

(ii) Ag ⁺ (aq) and Cu(s)

(iii) Fe^{3 +} (aq) and Br^– (aq)

(iv) Ag(s) and Fe^{3 +} (aq)

(v) Br₂ (aq) and Fe^{2 +} (aq).

Predict the products of electrolysis in each of the following:

(i) An aqueous solution of AgNO₃ with silver electrodes.

(ii) An aqueous solution of AgNO₃ with platinum electrodes.

(iii) A dilute solution of H₂SO₄ with platinum electrodes.

(iv) An aqueous solution of CuCl₂ with platinum electrodes.