Question

An organic compound having molecular mass $60$ is found to contain $C=20$%, $H=6.67$% and $N=46.67$%, while rest is oxygen. On heating, it gives $N{H}_3$ along with a solid residue. The solid residue gives violet colour with alkaline copper sulphate solution. The compound is:

• A. $C{H}_{3}NCO$
• B. $C{H}_{3}CON{H}_2$
• C. $(N{H}_2{)}_{2}CO$
• D. $C{H}_{3}C{H}_{2}CON{H}_2$

Answer 1

The correct option is C $(N{H}_2{)}_{2}CO$

The ratio of the number of gram atoms among $C$, $H$, $N$ and $O$ is,

$C:H:N:O=\frac{20}{12}:\frac{6.67}{1}:\frac{46.67}{14}:\frac{26.66}{16}=1:4:2:1$

Empirical formula $=C{H}_4{N}_{2}O$. So, empirical weight $=60$ g.

Given, molecular weight $=60$ g.

$\text{Molecular formula}=(\text{Empirical formula}{)}_n$

$n=\frac{\text{Molecular weight}}{\text{Empirical weight}}=\frac{60}{60}=1$

So, molecular formula is $(N{H}_2{)}_{2}CO$.