An unsaturated hydrocarbon $X$ absorbs two hydrogen molecules on catalytic hydrogenation,and also gives the following reaction: $X$ $\xrightarrow[Zn/H_2O]{O_3} A$ $\xrightarrow{[Ag(NH_3)_2]^{+}} B$ ($3$-oxo-hexane dicarboxylic acid). $X$ will be

Write the main product of the given reactions:
$(1)$ $C_6H_5CH = CH_2 \xrightarrow{HBr}$
$(2)$ $C_4H_{10} \xrightarrow{\text{air}, \Delta}$

$CH_3-C(CH_3)=CH_2 + (CH_3)_3CH \xrightarrow[273 \ K]{HF} C_8H_{18} (A)$
Unknown $(A)$ in the above reaction is:

Arrange the following compounds in decreasing order of acidic character of $C-H$ bonds.
$CH_2=CH_2, CH_3-CH_3, C_6H_6, CH\equiv CH$

In laboratory burners,we use

For the following reaction scheme,percentage yields are given along the arrows. $x \ g$ and $y \ g$ are the masses of $R$ and $U$,respectively. (Molar mass of $H$,$C$,and $O$ are $1$,$12$,and $16 \ g \ mol^{-1}$ respectively). $(1)$ The value of $x$ is $(2)$ The value of $y$ is.