Q27 / 125 · BITSAT 2021 · Chemistry

When $\mathrm{C}_{2} \mathrm{H}_{2}, \mathrm{CH}_{4}$ and $\mathrm{C}_{2} \mathrm{H}_{4}$ pass through a test tube which has ammonical $\mathrm{Cu}_{2} \mathrm{Cl}_{2}$, find out which gas comes out unaffected from test tube?

  • A
    $\mathrm{C}_{2} \mathrm{H}_{2}$ and $\mathrm{CH}_{4}$
  • B
    $\mathrm{C}_{2} \mathrm{H}_{2}$ and $\mathrm{C}_{2} \mathrm{H}_{4}$
  • Correct answer
    C
    $\mathrm{C}_{2} \mathrm{H}_{4}$ and $\mathrm{CH}_{4}$
  • D
    $\mathrm{C}_{2} \mathrm{H}_{2}$

Solution

$\mathrm{C}_{2} \mathrm{H}_{2}$ forms copper acetylide with ammonical $\mathrm{Cu}_{2} \mathrm{Cl}_{2}$ $\begin{array}{l} \mathrm{Cu}_{2} \mathrm{Cl}_{2}+2 \mathrm{NH}_{4} \mathrm{OH} \rightarrow \mathrm{Cu}_{2} \mathrm{O}+\mathrm{H}_{2} \mathrm{O}+2 \mathrm{NH}_{4} \mathrm{Cl} \\ \mathrm{Cu}_{2} \mathrm{O}+\mathrm{C}_{2} \mathrm{H}_{2} \rightarrow \underset{\text { (copper acetylide) }}{\mathrm{Cu}_{2} \mathrm{C}_{2}}+\mathrm{H}_{2} \mathrm{O} \end{array}$

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

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