Why does ethyne (acetylene) burn with a sooty flame?

Explanation

Ethyne is weakly acidic (C-H has some polarity ) because the carbon atoms involved in the triple bond are sp hybridised. However, molecule as a whole is non-polar since it is linear. Therefore, HF forms hydrogen bonding with ethyne since it is also polar in nature.
`overset(delta+)H-overset(delta-)F....overset(delta+)H-overset(delta-)C-=overset(delta-)C-overset(delta+)H....overset(delta-)F-overset(delta+)H`