Question

${\mathrm{Mg}}_2{\mathrm{C}}_3$ reacts with water to form Propyne. ${\mathrm{C}}_3^{4-}$has

Answer 1

Production of alkynes:

1. When metal carbides combine with water to produce alkyne and hydroxide.
2. The Magnesium carbide reacts with water to give Magnesium hydroxide and propyne.$\underset{\mathrm{Magnessium}\mathrm{carbide}}{{\mathrm{Mg}}_2{\mathrm{C}}_3\left(\mathrm{s}\right)}+4\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}\to \underset{\mathrm{Magnesium}\mathrm{hydroxide}}{2\mathrm{Mg}{\left(\mathrm{OH}\right)}_2\left(\mathrm{l}\right)}+\underset{\mathrm{Propyne}}{{\mathrm{C}}_3{\mathrm{H}}_4\left(\mathrm{g}\right)}$
3. ${\mathrm{C}}_3^{4-}$is formed when four hydrogen atoms are removed from propyne. $\underset{\mathrm{Propyne}}{{\mathrm{CH}}_3-\mathrm{C}\equiv \mathrm{CH}}\stackrel{-4{\mathrm{H}}^{+}}{\to }{}^{2-}\mathrm{C}=\mathrm{C}={\mathrm{C}}^{2-}$
4. Sigma bonds are the single bonds that make up a compound. When a compound has two bonds, one is the sigma bond and the other is the pi bond. If a compound has three bonds, one is the sigma bond and the other two are the pi bonds.${}^{2-}\mathrm{C}=\mathrm{C}={\mathrm{C}}^{2-}$
5. According to the structure of ${\mathrm{C}}_3^{4-}$, it has two double bonds, since one double bond contains $1$ sigma and $1$ pi bonds, $2$ double bonds have $2$ sigma and $2$ pi bonds.

Therefore, there are $2$ sigma bonds and $2$ pi bonds in ${\mathrm{C}}_3^{4-}$ion.