Halide Ion Precipitation Test

Steps:

• Recall halogen reactivity decreases down the group: F > Cl > Br > I, so weaker halogens like Br₂ cannot displace stronger ones like Cl⁻.
• Identify standard tests: silver nitrate forms colored precipitates with halides (AgCl white, AgBr pale yellow/cream, AgI yellow).
• Evaluate reducing agent strength: halide ions' ability to reduce increases down the group (I⁻ > Br⁻ > Cl⁻ > F⁻) due to easier electron loss.
• Check electron gain: halogens gain electrons to form anions, not cations.

Why B is correct:

• Silver halides are insoluble; AgBr forms a white (or cream) precipitate via Ag⁺(aq) + Br⁻(aq) → AgBr(s), a standard qualitative test.

Why the others are wrong:

• A: Br₂ does oxidize Cl⁻? No, incorrect—Br₂ cannot displace Cl₂ from NaCl as Cl₂ is stronger oxidant; no reaction occurs.
• C: Fluorine forms F⁻ anions by gaining electrons, not cations (which lose electrons).
• D: I⁻ is stronger reducing agent than Cl⁻, as larger ions lose electrons more easily.

Final answer: B