Identify the correct statements from the following.
Choose the correct answer from the options given below:

Solution

Chemistry ma’am · 3 steps

Write the molecular formula of both molecules first. Isomers must match exactly before you name the type.

1. Formula first. Isomers share one molecular formula. Homologues differ by CH₂ and must also carry the same functional group. Count carbons in each skeletal structure before you judge the label.

   Statement	First molecule	Second molecule	Verdict
   A	pentan-3-one, C₅H₁₀O (C₂H₅-CO-C₂H₅)	pentan-2-one, C₅H₁₀O (C₃H₇-CO-CH₃)	Correct: same ketone group, different alkyl groups on each side, so metamers
   B	propyl cyanide, C₄H₇N (-C≡N)	propyl isocyanide, C₄H₇N (-N≡C)	Correct: same formula, different functional groups, so functional isomers
   C	butan-1-ol, C₄H₁₀O	pentan-2-ol, C₅H₁₂O	Wrong: the formulae differ, so they are not isomers at all
   D	butan-1-amine, C₄H₁₁N (1° amine)	ethylpropylamine, C₅H₁₃N (2° amine)	Wrong: they differ by CH₂, but -NH₂ and -NH⁻ are different functional groups

2. Why D fails. A homologous series keeps the same functional group and general formula. A primary and a secondary amine belong to different classes, so a difference of CH₂ alone does not make them homologues.
3. So. Only A and B are correct, which is option (d).

The idea to keep. Count carbons in skeletal structures before you name any relationship. Isomers need the same formula; homologues need the same functional group and a CH₂ difference.

Answer from the NTA final answer key. Solution by PrepWiser.