Certain organic compound on combustion produces three gaseous...

The elements present in organic compounds are C, H, S and their oxides are $C{O}_{2}, {H}_{2}O, S{O}_{2}$ respectively.
$C{O}_{2}$ turns lime water milky, water turns anhydrous copper sulphate blue and $S{O}_{2}$ being reducing agent can reduce ${K}_{2}C{r}_{2}{O}_{7}$ into green coloured $Cr^{3 +}$ compound $\left(CrC{l}_{3}\right)$ etc.