Question

The carbide of which of the following metals on hydrolysis gives allylene or propyne?

• A. $Be$
• B. $Ca$
• C. $Al$
• D. $Mg$

Answer 1

Answer: (D)

$Mg$

Answer 2

$Be_2C$ and $Al_4C_3$ on reaction with water liberate methane gas while $CaC_2$ gives acetylene gas. $Mg$ forms $MgC_2$ either when heated directly with carbon in an electric furnace or when $MgO$ is heated with carbon. When $MgC_2$ is heated, it changes into $Mg_2C_3$. The carbide, $Mg_2C_3$ reacts with $H_2O$ to form propyne. ${Mg2C3 +4H3O -> 2Mg(OH)2 + CH3C}$ $\underset{\text{Propyne}}{ {\equiv CH}}$