Relative acidities of alkanes, alkenes, and alkynes?

Question

How does one explain the trend in bond lengths and acidity of the following hydrocarbons?

Answer 1

The trend can generally be explained by looking at the hybridization. Alkanes are sp3 hybridized, alkenes are sp2 and alkynes are sp hybridized. Therefore, the triple bonds in alkynes contain more s-character than the double bonds in alkenes and single bonds in alkanes. The more s-character a bond has, the shorter it will be and the more acidic the molecule will be. This is because the electrons are closer to the nucleus when there is more s-character in a bond.