Why is the C-H bond length and strength different for ethyne, ethene and ethane?

The length and strength of the C-H bond are different for ethine, ethylene and ethane due to the difference between the s characters (sp 3, sp 2, sp) in each chemical structure, which gives stronger bonds. For example, the length of the C-H bond in ethino is 1.06Å, which is also less than in ethane (1.09Å) or ethylene (1.08Å).

Answer: The energy associated with a chemical bond formation determines the bond strength and its proportion/degree determines its bond length.

Explanation:

When the bond energy is higher, the 'stronger' we say the bond is between the two atoms become, and the distance between its atoms (bond length) is smaller.