10. Biomolecules — Chemistry STD 12 Science — Question

The reaction $X+Y^{2+} \rightarrow x^{2+} +Y$ will be spontaneous when :

$CH_3CH_2CH_2Br + NaCN \to $$CH_3CH_2CH_2CN+ NaBr$

This reaction will be the fastest in

$(I)\,\,HCHO$                                        $ (II)\,\,CH_3CHO$
$(III)$ Acetone                                      $\begin{array}{*{20}{c}}
  {\,\,\,\,\,\,\,\,\,\,\,\,\,O} \\ 
  {\,\,\,\,\,\,\,\,\,\,\,\,\,||} \\ 
  {(IV)\,\,\,Et - C - Et} 
\end{array}$