Acetylene shows acidic character because carbon is sp hybridized containing 50 % s-character which makes acirc; euro; ldquo;C-H bond highly acidic in nature.In acetylene carbon is sp hybridized. The bond length sp<sp2<sp3. So sp bond is smallest the bonded pair in case of sp hybridized bond is nearer to C than in cases of sp2 snd sp3 bonds. So sp hybridized cabon is more electronegetive and can pull electron more nearer to the carbon and make hydrogen od actylene acquire a little positive charge. Thus the hydrogen become a little acidic in nature.