A solution contains NO 2 − and I − . To detect I − using the CCl 4 layer test, which of the following is true?

Question

A solution contains NO 2 − ​ and I − . To detect I − using the CCl 4 ​ layer test, which of the following is true?

TestHub · Accepted Answer

Concepts: Interference in anion analysis, redox stability.

Solution:

1. In the CCl₄ test, we usually add an oxidant like Cl₂ water to liberate I₂.

2. However, NO₂⁻ itself is an oxidant in acidic medium:

$H N O_{2} + I^{-} + H^{+} \to NO + I_{2} + H_{2} O$

3. Thus, NO₂⁻ will cause a "false positive" or premature liberation of I₂ even without adding Cl₂ water. It must be accounted for or removed.

Correct Answer: NO₂⁻ must be removed because it can oxidize I⁻ to I₂ in acidic medium.

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