A compound ' $\mathrm{X}^{\prime}$ upon reaction with $\mathrm{H}_2 \mathrm{O}$ produced a colourless gas ' $Y$ ' with rotten fish smell. Gas ' $\mathrm{Y}$ ' is absorbed in a solution of $\mathrm{CuSO}_4$ to give $\mathrm{Cu}_3 \mathrm{P}_2$ as one of the products. Predict the compound ' $\mathrm{X}$ '

• Correct answer
  A

  $\mathrm{Ca}_3 \mathrm{P}_2$
• B

  $\mathrm{NH}_4 \mathrm{Cl}$
• C

  $\mathrm{As}_2 \mathrm{O}_3$
• D

  $\mathrm{Ca}_3\left(\mathrm{PO}_4\right)_2$

Solution

$$ \text { The given road map problem is } $$
As compound ' $\mathrm{X}$ ' produces a colorless gas ' $\mathrm{Y}$ ' with rotten fish smell, it can be $\mathrm{Ca}_3 \mathrm{P}_2$ (calcium phosphide). The reaction takes palce as follows : $$ \mathrm{Ca}_3 \mathrm{P}_2+\mathrm{H}_2 \mathrm{O} \longrightarrow \mathrm{Ca}(\mathrm{OH})_2+\mathrm{PH}_3 $$ Colorless gas with rotten fish smell. ' $\mathrm{Y}$ ' $\mathrm{CuSO}_4+\underset{\mathrm{Y}^{\prime}}{\mathrm{PH}_3} \longrightarrow \mathrm{Cu}_3 \mathrm{P}_2+\mathrm{H}_2 \mathrm{SO}_4$

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