Q85 / 180 · NEET 2025 · Chemistry

Which one of the following reactions does NOT belong to "Lassaigne's test" ?

A
$\mathrm{Na}+\mathrm{C}+\mathrm{N} \xrightarrow[\Delta]{ } \mathrm{NaCN}$
B
$2 \mathrm{Na}+\mathrm{S} \xrightarrow[\Delta]{ } \mathrm{Na}_2 \mathrm{~S}$
C
$\mathrm{Na}+\mathrm{X} \xrightarrow[\Delta]{\longrightarrow}+\mathrm{NaX}$
Correct answer
D
$2 \mathrm{CuO}+\mathrm{C} \xrightarrow[\Delta]{ } 2 \mathrm{Cu}+\mathrm{CO}_2$

Solution

$2 \mathrm{CuO}+\mathrm{C} \xrightarrow[\Delta]{ } 2 \mathrm{Cu}+\mathrm{CO}_2$ "Lassaigne's test" is used to detect Nitrogen, Halogen, Sulphur, Phosphorus. $4^{\text {th }}$ option is detection of carbon, it is not "Lassaigne's test".

Hence, the correct answer is option: 'D'.

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