Q10 / 75 · JEE Main 2026 (02 April Shift 1) · Chemistry

Given below are two statements :
Statement (I) : Oxidising power of halogens decreases in the order $F_2 > Cl_2 > Br_2 > I_2$, which is the basis of "Layer test".
Statement (II) : "Layer test" to identify $Br_2$ and $I_2$ in aqueous solution involves the oxidation of bromide or iodide into $Br_2$ or $I_2$ respectively with $Cl_2$, which is a type of displacement redox reaction.
In the light of the above statements, choose the correct answer from the options given below :

  • Correct answer
    A
    Both Statement I and Statement II are true
  • 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

Solution

Statement I is true. The oxidising power of halogens decreases down the group in the order $F_2 > Cl_2 > Br_2 > I_2$. A stronger oxidising halogen can displace a weaker oxidising halogen from its aqueous halide solution. This principle forms the basis of the layer test.

Statement II is true. In the layer test, chlorine water ($Cl_2$) is added to an aqueous solution containing bromide ($Br^-$) or iodide ($I^-$) ions. Since $Cl_2$ is a stronger oxidising agent, it oxidises $Br^-$ to $Br_2$ and $I^-$ to $I_2$. The reaction is given by:
$Cl_2 + 2X^- \rightarrow 2Cl^- + X_2$ (where $X = Br, I$)
This is a non-metal displacement redox reaction. The liberated $Br_2$ or $I_2$ is then extracted into an organic solvent layer (like $CHCl_3$ or $CCl_4$), where it imparts a characteristic orange-red colour for $Br_2$ or a violet colour for $I_2$, thereby identifying them.

Therefore, both Statement I and Statement II are true.

Answer: Both Statement I and Statement II are true

Hence, the correct answer is option: 'A'.

Relevant Questions