Which one of the following reactions does NOT belong to "Lassaigne's test"? (1) Na + C + N δ NaCN; (2) 2Na + S δ Na2S; (3) Na + X…

Question

Which one of the following reactions does NOT belong to "Lassaigne's test"? (1) Na + C + N δ NaCN; (2) 2Na + S δ Na2S; (3) Na + X δ NaX; (4) 2CuO + C δ 2Cu + CO2.

1. A. Na + C + N NaCN
2. B. 2Na + S Na2S
3. C. Na + X NaX
4. D. 2CuO + C 2Cu + CO2 (Correct answer)

Correct Answer

Option D — 2CuO + C 2Cu + CO2

Detailed Solution & Explanation

The correct answer is 2CuO + C $\to$ 2Cu + CO$_2$.

Key Points

• Lassaigne's (sodium fusion) test detects N, S, halogens and P in an organic compound by fusing it with sodium: Na + C + N $\to$ NaCN, 2Na + S $\to$ Na$_2$S, Na + X $\to$ NaX.
• The reaction 2CuO + C $\to$ 2Cu + CO$_2$ is a simple reduction of copper oxide by carbon and has nothing to do with Lassaigne's test.