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ChemMedMain 2026 • 2nd Apr - Shift 1

Evaluation of Halogen Oxidizing Power and Layer Test Statements

Given below are two statements : Statement (I) : Oxidising power of halogens decreases in the order F2>Cl2>Br2>I2\text{F}_2 > \text{Cl}_2 > \text{Br}_2 > \text{I}_2, which is the basis of "Layer test". Statement (II) : "Layer test" to identify Br2\text{Br}_2 and I2\text{I}_2 in aqueous solution involves the oxidation of bromide or iodide into Br2\text{Br}_2 or I2\text{I}_2 respectively with Cl2\text{Cl}_2, which is a type of displacement redox reaction. In the light of the above statements, choose the correct answer from the options given below :

Options

A

Both Statement I and Statement II are true

Correct
B

Both Statement I and Statement II are false

C

Statement I is true but Statement II is false

D

Statement I is false but Statement II is true

Topics & Concepts

p-Block Elements (Group 15-18)p-Block ElementsBalancing Redox ReactionsOxidation State

Step-by-Step Solution

To evaluate the correctness of the given statements, let us analyze the properties of halogens and the mechanism of the "Layer test":

  1. Analysis of Statement (I): The oxidizing power of halogens is determined by their standard electrode reduction potentials (Ereduction∘E^\circ_{\text{reduction}}): EF2/F−∘=+2.87 VE^\circ_{\text{F}_2/\text{F}^-} = +2.87\text{ V} ECl2/Cl−∘=+1.36 VE^\circ_{\text{Cl}_2/\text{Cl}^-} = +1.36\text{ V} EBr2/Br−∘=+1.09 VE^\circ_{\text{Br}_2/\text{Br}^-} = +1.09\text{ V} EI2/I−∘=+0.54 VE^\circ_{\text{I}_2/\text{I}^-} = +0.54\text{ V}

    Since a higher reduction potential indicates a stronger oxidizing power, the tendency to accept electrons decreases down Group 17 in the order: F2>Cl2>Br2>I2\text{F}_2 > \text{Cl}_2 > \text{Br}_2 > \text{I}_2

    Because of this variation in oxidizing power, a halogen with a higher reduction potential can oxidize the halide ions derived from halogens located below it in the periodic table. This principle forms the basis of the "Layer test" used in qualitative inorganic analysis. Thus, Statement (I) is True.

  2. Analysis of Statement (II): In the "Layer test", chlorine water (Cl2\text{Cl}_2) is added to an aqueous solution containing bromide (Br−\text{Br}^-) or iodide (I−\text{I}^-) ions in the presence of an immiscible organic solvent such as CCl4\text{CCl}_4, CHCl3\text{CHCl}_3, or CS2\text{CS}_2.

    Chlorine, being a stronger oxidizing agent than Br2\text{Br}_2 and I2\text{I}_2, oxidizes these ions via a displacement redox reaction: 2Br−(aq)+Cl2(aq)→Br2(aq)+2Cl−(aq)2\text{Br}^-(aq) + \text{Cl}_2(aq) \rightarrow \text{Br}_2(aq) + 2\text{Cl}^-(aq) 2I−(aq)+Cl2(aq)→I2(aq)+2Cl−(aq)2\text{I}^-(aq) + \text{Cl}_2(aq) \rightarrow \text{I}_2(aq) + 2\text{Cl}^-(aq)

    The liberated non-polar Br2\text{Br}_2 or I2\text{I}_2 dissolves preferentially in the organic layer:

    • Br2\text{Br}_2 imparts an orange or reddish-brown color to the organic layer.
    • I2\text{I}_2 imparts a violet color to the organic layer.

    Since Cl2\text{Cl}_2 displaces bromide or iodide ions from their solution through an electron-transfer (redox) mechanism, this is indeed a displacement redox reaction. Thus, Statement (II) is True.

Conclusion: Both Statement I and Statement II are true.

Correct Option: A

Evaluation of Halogen Oxidizing Power and Layer Test Statements | Chemistry PYQ Solution - JEE Challenger