Write the following reactions:
$(1)$ Ethyne $+$ $(Cl_2 \text{ or } Br_2)$
$(2)$ Hydration reaction of but$-1-$yne.

(N/A) $(i)$ Reaction of ethyne with chlorine in the presence of water:
$HC \equiv CH$ $\xrightarrow{Cl^+ - OH^- (Cl_2 + H_2O)} CHOH = CHCl$ $\xrightarrow{Cl^+ - OH^-} [CH(OH)_2 - CHCl_2]$ $\xrightarrow{-H_2O} CHCl_2CHO$ ($2,2-$dichloroethanal).
$(ii)$ Hydration of but$-1-$yne:
$CH_3CH_2C \equiv CH$ $\xrightarrow{+H_2O, Hg^{2+}, \text{dil. } H_2SO_4} CH_3CH_2C(OH) = CH_2 \rightleftharpoons CH_3CH_2COCH_3$ (butanone).