Question

$HCN+H_{2}O \rightarrow \left[X\right]+NH_{3}\text{,}$

$\left[X\right] \rightarrow \left[Y\right]+H_{2}O \, \left(U n b a l a n c e d \, e q u a t i o n s\right)$

[Y] May be prepared by which one of the following methods?

• A. By dehydration of Malonic acid with $P_{2}O_{5}$
• B. By thermal decomposition of carbon sub-oxide in air.
• C. By heating potassium hexacyanoferrate (II) with conc. $H_{2}SO_{4}$ .
• D. By the action of conc. $HNO_{3}$ on charcoal.

Answer 1

Answer: (C)

$HCN\text{ + }2H_{2}O \rightarrow HCOOH\left(X\right)\text{ + }2NH_{3};$

$HCOOH\overset{\Delta }{ \rightarrow }CO\left[Y\right]\text{+}H_{2}O$

(iii) Only $K_{4}\left(F e \left(C N\right)_{6}\right)$ gives $CO$ with conc. $H_{2}SO_{4}$ according to the following reaction.

$K_{4}\left[F e \left(C N\right)_{6}\right]\text{+}6H_{2}SO_{4}\left(c o n c .\right)\text{ + }6H_{2}O \rightarrow 2K_{2}SO_{4}+FeSO_{4}+3\left(N H_{4}\right)_{2}SO_{4}+6CO$

(i) Malonic acid gives $C_{3}O_{2}$ ;

(ii) $C_{3}O_{2}$ gives $CO_{2}$ .

(iv) Action of conc. $HNO_{3}$ on charcoal gives $CO_{2}$ .