X→1% HgSO4,  60°C30% H2SO4Yintermediate⇌Zfinal If Z is aldehyde, X is

CH≡CH+H2O⇌Hg+2, 60oC30%H2SO4CH|H=COH|H⇌tautomerismketo−enolCH3−CHOR−C≡CH+H2O⇌Hg+2, 60oC30%H2SO4R−COH|=CH|H⇌tautomerismketo−enolR−CO−CH3Addition of water follows Markownikov’s rule. So in alkynes, the O – H group  (- negative part of addendum) attacks non – terminal carbon. Thus the final product is ketone.               ∵Ethyne contains only two carbon atoms, – OH group attacks terminal carbon. Thus the final product is an aldehyde