The product(s) obtained via oxymercuration (${\mathrm{HgSO}}_4+{\mathrm{H}}_2{\mathrm{SO}}_4$) of $1$-butyne would give 

When $2$-butyne is treated with dil. ${\mathrm{H}}_2{\mathrm{SO}}_4/{\mathrm{HgSO}}_4$, the product formed is 

In the following reaction:

${\mathrm{C}}_2{\mathrm{H}}_{2 } \underset{{\mathrm{HgSO}}_4/{\mathrm{H}}_2{\mathrm{SO}}_4 }{\overset{{\mathrm{H}}_2\mathrm{O}}{\to }} \mathrm{X} \rightleftharpoons {\mathrm{CH}}_3\mathrm{CHO}$

What is X ?

Identify the reagents in the following transformations: 

A compound $\mathrm{X}\hspace{0.17em}\left({\mathrm{C}}_5{\mathrm{H}}_8\right)$ reacts with ammoniacal ${\mathrm{AgNO}}_3$ to give a white precipitate, and on oxidation with hot alkaline ${\mathrm{KMnO}}_4$ gives the acid, $({\mathrm{CH}}_3{)}_2\mathrm{CHCOOH}$. Therefore, $\mathrm{X}$ is