$\begin{matrix}
CH-C{{O}_{2}}H \\
\,||\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \\
CH-C{{O}_{2}}H \\
\end{matrix}\xrightarrow[(two\,mole)]{NaOH}(A)\xrightarrow{electrolysis}(B);$
$CaO + C\xrightarrow{{Heat}}A\xrightarrow{{{H_2}O}}B\xrightarrow{{{H_2}S{O_4}\,;\,H{g^{2 + }}}}C$