Question

The number of $\sigma$ and $\pi$ bonds in ${C_2}{H_2}$ is:
(A) $0$ and $4$
(B) $2$ and $2$
(C) $3$ and $2$
(D) $4$ and $2$

Answer 1

To find the number of $\sigma$ and $\pi$ bonds in ${C_2}{H_2}$ we have to analyze the structure and hybridization of ${C_2}{H_2}$ and calculate the total number of bonds and then determine how many sigma and pi-bonds are present in the structure.

Complete step by step answer:
The chemical name of ${C_2}{H_2}$ is Ethyne. It is also called acetylene. It is an organic compound made up of carbon and hydrogen. It is the first member of the homologous series of alkynes.It is represented by the structure given below,

The nature of the bond found between carbon and hydrogen in ethyne is a covalent bond. The hybridization in carbon varies from $s{p^3}$ to $sp$. In case of Ethyne, the hybridization is $sp$. The geometry of the ethyne molecule is planar. In its excited state, carbon has one electron in $2s$ and three electrons in $2p$orbitals. Since two carbon atoms are present in the bonding so the one electron in $2s$orbitals forms a sigma bond with one electron in $1s$ orbital of Hydrogen and the two electrons in unhybrid $2p$ orbitals form two $\pi$ bonds with the two electrons present in$2p$orbitals of the second carbon atom. The remaining one electron forms a sigma bond with the other remaining electron. In this way, a triple bond is formed between two carbon atoms and two single bonds between carbon and hydrogen. Hence, among this one triple bond and two single bonds, the number of $\sigma$and $\pi$ bonds in ${C_2}{H_2}$ is $3$ and $2$.

So, the correct answer is Option C.

Note: Ethyne is a colorless gas. It is widely used as a fuel and a chemical building block. It is highly unstable in its pure form and thus generally handled as a solution. It is also used in various conversions in organic chemistry.