Question 57
An organic compound A on heating with concentrated ${\text{H}}_2{\text{SO}}_4$ forms a compound B which on an addition of one mole of hydrogen in presence of $\text{Ni}$ forms a compound C. One mole of compound C on combustion forms two moles of ${\text{CO}}_2$ and 3 moles of ${\text{H}}_2\text{O}$. Identify the compounds A, B and C and write the chemical equations of the reactions involved.

Since compound C gives 2 moles of ${\text{CO}}_2$ and 3 moles of ${\text{H}}_2\text{O}$, it shows that it has the molecular formula ${\text{C}}_2{\text{H}}_6$ (Ethane). The reaction involved is:

$2{\text{C}}_2{\text{H}}_6+7{\text{O}}_2\to 4{\text{CO}}_2+6{\text{H}}_2\text{O}+\text{Heat}+\text{Light}$

'C' is obtained by the addition of one mole of hydrogen to compound B so the molecular formula of B should be ${\text{C}}_2{\text{H}}_4$ (Ethene). The reaction involved is:

${\text{C}}_2{\text{H}}_4+{\text{H}}_2\stackrel{\text{Ni}}{\to }4{\text{CO}}_2+6{\text{H}}_2\text{O}+\text{Heat}+\text{Light}$


Compound B is obtained by heating compound A with concentrated ${\text{H}}_2{\text{SO}}_4$ which shows it to be an alcohol. So compound A could be ${\text{C}}_2{\text{H}}_5\text{OH}$ (Ethanol). The reaction involved is:

${\text{C}}_2{\text{H}}_5\text{OH}\stackrel{{\text{Hot conc. H}}_2{\text{SO}}_4}{⟶}{\text{C}}_2{\text{H}}_4+{\text{H}}_2\text{O}$