Practicing Success

Target Exam

CUET

Subject

Chemistry

Chapter

Physical: Electro Chemistry

Question:

Match the entries of column I with appropriate entries of column II and choose the correct option out of the four options given.

Column I

(Electrolysis)

Column II

(Products at anode and cathode respectively)

(a) NaCl solution using inert electrodes (i) O2 and Cu
(b) NaCl solution using Hg as cathode and graphite rod as anode (ii) O2 and H2
(c) Very dilute NaCl solution using inert electrodes (iii) Cl2 and Na
(d) CuSO4 solution using inert electrodes (iv) Cl2 and H2

 

Options:

(a)-(i), (b)-(iii), (c)-(ii), (d)-(iv)

(a)-(iii), (b)-(iv), (c)-(ii), (d)-(i)

(a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)

(a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)

Correct Answer:

(a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)

Explanation:

The correct answer is option 3. (a)-(iv), (b)-(iii), (c)-(ii), (d)-(i).

Column I

(Electrolysis)

Column II

(Products at anode and cathode respectively)

(a) NaCl solution using inert electrodes (iv) Cl2 and H2
(b) NaCl solution using Hg as cathode and graphite rod as anode (iii) Cl2 and Na
(c) Very dilute NaCl solution using inert electrodes (ii) O2 and H2
(d) CuSO4 solution using inert electrodes (i) O2 and Cu

Let us go through each case of electrolysis to understand the products formed at the anode and cathode.

(a) NaCl solution using inert electrodes

Inert Electrodes: These electrodes do not participate in the reaction and are typically made of materials like platinum or graphite.

At the anode (oxidation occurs):

\(2 \text{Cl}^- \rightarrow \text{Cl}_2 + 2e^-\)

Chloride ions (Cl\(^-\)) are oxidized to chlorine gas (Cl\(_2\)).

At the cathode (reduction occurs):

\(2 \text{H}_2\text{O} + 2e^- \rightarrow \text{H}_2 + 2 \text{OH}^-\)

Water is reduced to hydrogen gas (H\(_2\)) and hydroxide ions (OH\(^-\)).

Products:

Anode: Cl\(_2\)

Cathode: H\(_2\)

(b) NaCl solution using Hg as cathode and graphite rod as anode

Mercury (Hg) Cathode and Graphite Anode:

At the anode (oxidation occurs):

\(2 \text{Cl}^- \rightarrow \text{Cl}_2 + 2e^-\)

Chloride ions (Cl\(^-\)) are oxidized to chlorine gas (Cl\(_2\)).

At the cathode (reduction occurs):

\(\text{Na}^+ + e^- \rightarrow \text{Na (amalgam)}\)

Sodium ions (Na\(^+\)) are reduced to form a sodium amalgam with mercury (Na-Hg).

Products:

Anode: Cl\(_2\)

Cathode: Na (amalgam)

(c) Very dilute NaCl solution using inert electrodes

Inert Electrodes and Very Dilute NaCl Solution:

At the anode (oxidation occurs):

\(2 \text{H}_2\text{O} \rightarrow \text{O}_2 + 4 \text{H}^+ + 4e^-\)

Water is oxidized to oxygen gas (O\(_2\)).

At the cathode (reduction occurs):

\(2 \text{H}_2\text{O} + 2e^- \rightarrow \text{H}_2 + 2 \text{OH}^- \)

Water is reduced to hydrogen gas (H\(_2\)) and hydroxide ions (OH\(^-\)).

Products:

Anode: O\(_2\)

Cathode: H\(_2\)

(d) CuSO\(_4\) solution using inert electrodes

Inert Electrodes and CuSO\(_4\) Solution:

At the anode (oxidation occurs):

\(2 \text{H}_2\text{O} \rightarrow \text{O}_2 + 4 \text{H}^+ + 4e^-\)

Water is oxidized to oxygen gas (O\(_2\)).

At the cathode (reduction occurs):

\(\text{Cu}^{2+} + 2e^- \rightarrow \text{Cu}\)

Copper ions (Cu\(^{2+}\)) are reduced to copper metal (Cu).

Products:

Anode: O\(_2\)