Which of the following best describes the nucleophilic addition step in the acid-catalyzed hydrolysis of acetonitrile $(CH_3CN)$?

Identify the correct decreasing order of boiling points for the following organic compounds.

Ethyl ester $\xrightarrow{CH_3MgBr \text{ (excess)}} P$. The product $P$ will be

What are $\underline{A}, \underline{B}, \underline{C}$ in the following reactions?
$(I)$ $(CH_3 CO_2)_2 Ca \stackrel{\Delta}{\longrightarrow} \underline{A}$
$(II)$ $CH_3 CO_2 H \underset{\text{Red P}}{\stackrel{HI}{\longrightarrow}} \underline{B}$
$(III)$ $2 CH_3 CO_2 H \stackrel{P_4 O_{10}}{\longrightarrow} \underline{C}$
$\underline{A} \quad \underline{B} \quad \underline{C}$

The major product of the following reaction sequence is

$(i) \ F_3CCOOH$
$(ii) \ CH_3COOH$
$(iii) \ C_6H_5COOH$
$(iv) \ CH_3CH_2COOH$
Correct order of $pK_a$ value is: