Q.Cis-2-butene and trans-2-butene are

Ethylene (C2H4) is about 85.7% carbon by mass, and propene (C3H6) has exactly the same percentage because both share the empirical formula CH2.

First find %C in ethylene, C2H4 (molar mass = 2(12) + 4(1) = 28 g/mol):

%C = (24/28) x 100 = 85.7%

Now check each option (using C=12, H=1):

• Benzene, C6H6 (M = 78): %C = (72/78) x 100 = 92.3% — does not match.
• Propene, C3H6 (M = 42): %C = (36/42) x 100 = 85.7% — matches exactly.
• Ethane, C2H6 (M = 30): %C = (24/30) x 100 = 80.0% — does not match.
• Ethyne, C2H2 (M = 26): %C = (24/26) x 100 = 92.3% — does not match. …

Propene (C3H6) has the same percentage of carbon (about 85.7%) as ethylene (C2H4), because both share the empirical formula CH2.

First find %C in ethylene, C2H4 (molar mass = 2(12) + 4(1) = 28):

%C = 24/28 × 100 ≈ 85.7%

Now check each option (molar mass, then %C):

• Benzene, C6H6 (78 g/mol): %C = 72/78 × 100 ≈ 92.3% — different.
• Ethane, C2H6 (30 g/mol): %C = 24/30 × 100 = 80.0% — different. …