Question
A student was given the compound C6H4(NH2)SO3H for elemental analysis, while performing Lassaigne's test for 'N' what colour will he get and why?
✓
Answer
Blood red colouration, he will get because compound contains both N and S.
$\text{Na}+\text{S}+\text{C}+\text{N}\xrightarrow{\ \ \ \ \ \ \ \ \ \ }\text{NaSCN}$
$\text{Fe}+\text{3NaSCN}\xrightarrow{\ \ \ \ \ \ \ \ \ \ }\text{Fe}(\text{SCN})_3+3\text{Na}^+\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{Blood red colour}$
$\text{Na}+\text{S}+\text{C}+\text{N}\xrightarrow{\ \ \ \ \ \ \ \ \ \ }\text{NaSCN}$
$\text{Fe}+\text{3NaSCN}\xrightarrow{\ \ \ \ \ \ \ \ \ \ }\text{Fe}(\text{SCN})_3+3\text{Na}^+\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{Blood red colour}$
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