Arrange benzene ,n-hexane and ethyne in decreasing order of acidic behaviour. Also reason for this behaviour.

Explanation

The hybridisation state of carbon in the compounds benzene, n-hexane and ethyne are as follows-

With increase in the s-character of the orbital involved in formation of `C-H` bonds, the electrons of the `C-H` bond lie more close to the carbon atom because s-electrons are close to the nucleus. Thus, the correct order of decreasing acidic behaviour is: ethyne `gt` benzene `gt` n-hexane.