Bromine Partitioning Based on Polarity

Steps:

• Bromine (Br₂) is a non-polar molecule due to its covalent bonding.
• Cyclohexane is a non-polar hydrocarbon solvent.
• Water is a polar solvent, immiscible with cyclohexane.
• Upon shaking and settling, Br₂ dissolves preferentially in the non-polar cyclohexane layer via "like dissolves like," coloring it while leaving the aqueous layer colorless.

Why B is correct:

• Non-polar Br₂ molecules partition into non-polar cyclohexane, explaining the color distribution per the solubility principle that like dissolves like.

Why the others are wrong:

• A: Reduction to bromide ions would decolorize the solution entirely, not concentrate color in the organic layer.
• C: Bromine has low reactivity with water under these conditions, and its solubility in cyclohexane causes the observed layering.
• D: No reaction occurs with cyclohexane (an alkane) without catalysts; the color is from dissolved Br₂, not a product.

Final answer: B