Question

When a mixture of potassium cyanate and ammonium sulphate is heated, it gives:
A. urea
B. methanamide
C. ethanamide
D. none

Answer 1

Hint: A solution of potassium cyanate and ammonium sulphate is evaporated to dryness leading to the formation of ammonium cyanate. It then undergoes rearrangement.


Complete answer:
Urea is the main nitrogen-containing end product of the breakdown of protein metabolism in all mammals and some fish. The material is not only in the urine of all mammals, but also in their blood, bile, milk, and sweat. Urea was first isolated from urine in 1773 by the French chemist Hilaire-Marin Rouelle.
During protein breakdown, amino acids ($NH_2$) are removed from amino acids that partially contain the protein. These amino groups are converted to ammonia ($NH_2$), which is toxic to the body and thus must be converted into urea by the liver. Urea has important uses as a fertilizer and feed supplement, as well as a starting material for the manufacture of plastics and drugs
A solution of potassium cyanate and ammonium sulfate evaporated to dryness when ammonium cyanate is formed, which then undergoes rearrangement to form urea.
${\text{2KCNO + (N}}{{\text{H}}_4}{)_2}{\text{S}}{{\text{O}}_4}{\text{ }} \to {\text{ 2N}}{{\text{H}}_4}{\text{CNO + }}{{\text{K}}_2}{\text{S}}{{\text{O}}_4}$

$ NH_4CNO\xrightarrow{rearrange} H_2NCONH_2$

So, the correct answer is Option A.

Note: Potassium cyanate is used as a raw material for organic synthesis, pharmaceutical and herbicide whereas ammonium sulphate is used as a fertilizer for alkaline solids. Also Urea is a colourless, crystalline substance that melts at 132.7 degree Celsius.