How can methanol and ethanol be distinguished?
A) Treating with Schiff’s reagent
B) Treating with Lucas reagent
C) Heating with iodine and alkali
D) Treating with CrO₂ in dilute H₂SO₄

Methanol and ethanol can be distinguished by their reactions with certain reagents. Let's evaluate each option:

A) Treating with Schiff’s reagent: Schiff's reagent is typically used to test for the presence of aldehydes. Both methanol and ethanol are not aldehydes, so this test would not help distinguish between them.

B) Treating with Lucas reagent: Lucas reagent is used to test for the presence of primary, secondary, and tertiary alcohols. Methanol is a primary alcohol, and ethanol is also a primary alcohol. Therefore, the Lucas reagent test would not distinguish between methanol and ethanol.

C) Heating with iodine and alkali: This test is used to distinguish between primary, secondary, and tertiary alcohols. Methanol is a primary alcohol, and ethanol is also a primary alcohol. So, this test would not distinguish between methanol and ethanol.

D) Treating with Cr{O_2} in dil. {H_2}S{O_4}: This test involves using chromic acid in dilute sulfuric acid to oxidize the alcohol. Primary alcohols like methanol are oxidized to aldehydes and then to carboxylic acids, while secondary alcohols like ethanol are oxidized to ketones. So, if you perform this test, methanol would give different oxidation products compared to ethanol, allowing you to distinguish between them.

Therefore, the correct answer is D) Treating with Cr{O_2} in dil. {H_2}S{O_4}.