Carbon And Its Compounds Test - 2

Benzenoid compounds are generally aromatic.

Methane is a saturated hydrocarbon and will undergo substitution reaction, not addition reaction.

Unsaturated compounds undergo addition reactions with halogens.
Bromine water test is a distinction test for unsaturation, as the reddish brown colour of bromine water is discharged as bromine is added to the double bonded carbon atoms.

C₅H₁₀, pentene undergoes addition reaction with bromine and decolourizes bromine water.

Hence, option (4) is correct.

All the other options represent alkanes which are saturated hydrocarbons.

Glacial acetic acid is the purest form of acetic acid, which freezes during winters in regions with cold climate and resembles a glacier of ice.

Both litmus solution and NaHCO₃ can be used to distinguish between an alcohol and a carboxylic acid.

Only carboxylic acid will turn blue litmus red.
Only carboxylic acid will give effervescence with NaHCO₃ due to the evolution of CO₂.

Example:
CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂

However, both alcohols and carboxylic acids will produce an effervescence with Na metal due to the evolution of H₂ gas; hence, this reaction will not help to identify the compound.

Mixture of soap in water is a colloid as the soap micelles formed are in the colloidal range ( 1 nm to 10³ nm) and behave as colloidal particles.

Hence, option (4) is incorrect, regarding a mixture of soap in water.

All other statements are correct with reference to soap.
Soap is a sodium salt of higher carboxylic acids; it is a basic salt and its solution will have a pH more than 7.

Soap produces lather with soft water but not with hard water, because the corresponding calcium and magnesium salts are insoluble in water.