Q41 / 180 · AIIMS 2019 (25 May) · Chemistry
Which of the following are formula of methanides?
(1) $\mathrm{Be}_2 \mathrm{C}$
(2) $\mathrm{CaC}_2$
(3) $\mathrm{Mg}_2 \mathrm{C}_3$
(4) $\mathrm{Al}_4 \mathrm{C}_3$
- Correct answerAOnly 1 and 4
- BOnly 1 and 2
- COnly 3 and 4
- DOnly 2 and 4
Solution
Methanides are carbides which on hydrolysis give methane.
$\begin{aligned} & \mathrm{Be}_2 \mathrm{C}+4 \mathrm{H}_2 \mathrm{O} \longrightarrow 2 \mathrm{Be}(\mathrm{OH})_2+\mathrm{CH}_4 \\ & \mathrm{CaC}_2+2 \mathrm{H}_2 \mathrm{O} \longrightarrow \mathrm{Ca}(\mathrm{OH})_2+\mathrm{C}_2 \mathrm{H}_2 \\ & \mathrm{Mg}_2 \mathrm{C}_3+4 \mathrm{H}_2 \mathrm{O} \longrightarrow 2 \mathrm{Mg}(\mathrm{OH})_2+\mathrm{C}_3 \mathrm{H}_4 \\ & \mathrm{Al}_4 \mathrm{C}_3+12 \mathrm{H}_2 \mathrm{O} \longrightarrow 4 \mathrm{Al}(\mathrm{OH})_3+3 \mathrm{CH}_4\end{aligned}$
Hence, the correct answer is option: 'A'.