Question

An organic compound A on heating with concentrated $H_{2}S{O}_4$ forms a compound B which on addition of one mole of hydrogen in presence of Ni forms a compound C. One mole of compound C on combustion forms two moles of $C{O}_2$ and 3 moles of $H_{2}O.$ Identify the compounds A, B.

• A. A = Ethane , B = Ethanol
• B. A = Ethane , B = Ethene
• C. A = Ethanol , B = Ethene
• D. A = Ethanol , B = Ethane

Answer 1

The correct option is C A = Ethanol , B = Ethene

Since compound C gives 2 moles of $C{O}_2$ and 3 moles of $H_{2}O,$ it shows that it has the molecular formula $C_2{H}_6$ (Ethane). C is obtained by the addition of one mole of hydrogen to compound B so the molecular formula of B should be $C_2{H}_4$ (Ethene). Compound B is obtained by heating compound A with concentrated $H_{2}S{O}_4$ which shows it to be an alcohol. So compound A could be $C_2{H}_{5}OH$.
(Ethanol)
$C_2{H}_{5}OH\stackrel{Hotconc.H_{2}S{O}_4}{\to }{C}_2{H}_4+H_{2}O$
A B
$C_2{H}_4+H_2\stackrel{Ni}{\to }{C}_2{H}_6$
B C
$2C_2{H}_6+7O_2\to 4C{O}_2+6H_{2}O+$ Heat and light
C