An organic compound having molecular mass 60 is found to contain $\mathrm{C}=20 \%, \mathrm{H}= 6.67 \%$ and $\mathrm{N}=46.67 \%$ while rest is oxygen. On heating it gives $\mathrm{NH}_{3}$ alongwith a solid residue. The solid residue give violet colour with alkaline copper sulphate solution. The compound is

(C) $(\mathrm{NH}_{2})_{2} \mathrm{CO}$

(A) $\mathrm{CH}_{3} \mathrm{NCO}$

(B) $\mathrm{CH}_{3} \mathrm{CONH}_{2}$

(D) $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CONH}_{2}$

JEE Main · 2005 · 08 May 2005 · Offline · Some Basic Concepts of Chemistry

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

NH_{3}

alongwith a solid residue. The solid residue give violet colour with alkaline copper sulphate solution. The compound is

(A) $CH_{3} NCO$
(B) $CH_{3} CONH_{2}$
(C) $(NH_{2})_{2} CO$ ✓ Correct
(D) $CH_{3} CH_{2} CONH_{2}$

Answer: (C)

Solution

First turn the percentages into a formula for a molar mass of

60

: carbon at

20%

gives

\frac{0.20 \times 60}{12} = 1

atom, hydrogen at

6.67%

gives

4

, nitrogen at

46.67%

gives

2

, and the remaining

26.7%

oxygen gives

1

, so the molecule is

CH X_{4} N X_{2} O

. That formula is urea,

(NH X_{2}) X_{2} CO

. On heating it gives off ammonia and leaves a residue whose biuret test, a violet colour with alkaline copper sulphate, confirms the identification as urea.

JEE Main · 2005 · 08 May 2005 · Offline · Single correct option

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JEE Main · 2005 · 08 May 2005 · Offline · Some Basic Concepts of Chemistry

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