The incorrect statement regarding ethyne is
- The carbon-carbon bond in ethyne is weaker than that in ethene
- Both carbons are sp hybridised
- The C-C bond in ethyne is shorter than that in ethene
- Ethyne is linear
Answer
(1) The carbon-carbon bond in ethyne is weaker than that in ethene
Solution
Ethyne H-C C-H has one σ and two π bonds between the carbons; ethene has one σ and one π bond.
(1): more bonds hold the carbons, so C≡C (bond enthalpy 823 kJ mol-1) is stronger than C=C ( 681 kJ mol-1); hence (1) is incorrect.
(2): each carbon forms two σ bonds, so it is sp hybridised; hence (2) is correct.
(3): C≡C (120 pm) is shorter than C=C (134 pm), so (3) is correct.
(4): sp carbons give a 180° bond angle, so (4) is correct.
Answer: (1)