Question:
Sodium extract of thiourea will be ……… colour in Lassaigne's test.
Sodium extract of thiourea will be ……… colour in Lassaigne's test.
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Compounds with both N and S give blood red colour with \(\mathrm{Fe^{3+}}\) in Lassaigne's test.
Updated On: Apr 23, 2026
- blue
- red
- yellow
- green
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Verified By Collegedunia
The Correct Option is B
Solution and Explanation
Step 1: Formula / Definition}
\[ \text{Thiourea contains both } \mathrm{N} \text{ and } \mathrm{S} \]
Step 2: Calculation / Simplification}
Sodium fusion converts \(\mathrm{N}\) and \(\mathrm{S}\) to \(\mathrm{NaCNS}\) (thiocyanate).
\(\mathrm{NaCNS} + \mathrm{Fe^{3+}} \rightarrow [\mathrm{Fe(CNS)}]^{2+}\) (blood red colour).
Step 3: Final Answer
\[ \text{red} \]
\[ \text{Thiourea contains both } \mathrm{N} \text{ and } \mathrm{S} \]
Step 2: Calculation / Simplification}
Sodium fusion converts \(\mathrm{N}\) and \(\mathrm{S}\) to \(\mathrm{NaCNS}\) (thiocyanate).
\(\mathrm{NaCNS} + \mathrm{Fe^{3+}} \rightarrow [\mathrm{Fe(CNS)}]^{2+}\) (blood red colour).
Step 3: Final Answer
\[ \text{red} \]
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