(N/A) In an organic compound,carbon and hydrogen are detected by heating the compound with copper$(II)$ oxide $(CuO)$.
$i$. Detection of carbon: Carbon present in the compound is oxidized to carbon dioxide $(CO_2)$,which turns lime water milky due to the formation of calcium carbonate.
Reaction: $C + 2CuO \rightarrow 2Cu + CO_{2(g)}$
$CO_{2(g)} + Ca(OH)_{2(aq)} \rightarrow CaCO_{3(s)} + H_2O_{(l)}$
$ii$. Detection of hydrogen: Hydrogen present in the compound is oxidized to water $(H_2O)$. This water is tested using anhydrous copper$(II)$ sulphate $(CuSO_4)$,which turns blue due to the formation of hydrated copper sulphate.
Reaction: $2H + CuO \xrightarrow{\Delta} Cu + H_2O$
$5H_2O + CuSO_{4(white)} \rightarrow CuSO_4 \cdot 5H_2O_{(blue)}$