Reduction of nitroalkanes in neutral medium (e.g. Zn / N H_4 Cl) …

$\begin{array}{*{20}{c}}
{O\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,C \equiv CH\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,O\,\,\,} \\
{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,||\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,||\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\
{Cl - C - C{H_2} - C - C{H_2} - C{H_2} - C - C{H_3}} \\
{|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\
{C{H_2}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\
{|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\
{C \equiv N\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}
\end{array}$ $\xrightarrow[{BaS{O_4}}]{{{H_2}/Pd}}\,'X'$

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Which of the following compound is most acidic

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The reaction of hydrogen and iodine monochloride is given as

$H{_2(g)} + 2ICl_{(g)} \to 2HCl_{(g)} + I_{2(g)}$

This reaction is of first order with respect to $H_{2(g)}$ and $ICl_{(g)}$ , following mechanisms were proposed

Mechanism $A$ :

$H{_2(g)} + 2ICl_{(g)} \to 2HCl_{(g)} + I_{2(g)}$

Mechanism $B$ :

$H_{2(g)} + ICl_{(g)} \to HCl_{(g)} + HI_{(g)}$ ; Slow

$HI_{(g)} + ICl_{(g)} \to HCl_{(g)} + I_{2(g)}$ ; Fast

Which of the above mechanism $(s)$ can be consistent with the given information about the reaction