Structural Isomers of Butane

Steps:

• Identify structures: H3C-CH2-CH2-CH3 is n-butane (C4H10); H3C-CH-CH3 (H below) is 2-methylpropane (C4H10).
• Check empirical formula: Both C4H10 simplify to C2H5, so same empirical formula (statement 1 true).
• Check molecular formula: Both C4H10, so same molecular formula (statement 2 false).
• Check homologous series: Both saturated alkanes (CnH2n+2), so same series (statement 3 true).

Why B is correct:

• B selects statements 1 and 3, matching isomers' shared empirical formula and homologous series per alkane definition.

Why the others are wrong:

• A includes 2, but isomers have identical molecular formulas (C4H10).
• C excludes 3, but both are alkanes in the same series.
• D includes 2 (false, same molecular formula) and excludes 1 (false, same empirical formula).

Final answer: B