Question

If an adding of $FeC{l}_3$ solution to acidified Lassaigne s solution, a red colouration is produced, it indicates the presence of:

• A. $S$
• B. $N$
• C. $N$ and $S$
• D. $S$ and $Cl$

Answer 1

Answer: (C)

$N$ and $S$

The red colour is due to the formation of $Fe{\left(CNS\right)}_3$ which indicates the presence of both, $N$ and $S$ and the extract used will be $NaCNS$.

$Fe{Cl}_3+3NaCNS⟶\underset{\text{Blood red colour}}{Fe{\left(CNS\right)}_3}+3NaCl$