Question

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

$HCN\text{ + }2H_{2}O \rightarrow HCOOH\left(X\right)\text{ + }2NH_{3};$
$HCOOH\xrightarrow{\Delta }CO\left[Y\right]\text{+}H_{2}O$
(i) Malonic acid on dehydration by $P_{2}O_{5}$ produce $C_{3}O_{2}$ .
(ii) Carbon suboxide gives $CO_{2}$ on dissociation.
(iii) Potassium ferrocyanide on reaction with concentrated sulphuric acid produce $CO$ gas.
(iv) Action of concentrated $HNO_{3}$ on charcoal gives $CO_{2}$ .