Question: why hgso4 is used in hydration of alkynes?
Answer: The metal catalyst like HgSO4 or CdSO4 will act as promoter and enhance the rate of electrophillic additon. Direct addtion of electrophillic reagent will have low rate of reaction. ... It is used as reagent in hydration of alkyne. This reagent favors formation of aldehydes & ketones via enol tautomerisation.