Concept: Hybridization is the concept of mixing atomic orbitals to form new hybrid orbitals suitable for the pairing of electrons to form chemical bonds. The type of hybridization (sp, sp\u00b2, sp\u00b3) depends on the number of sigma bonds and lone pairs around the central atom. For carbon, if it forms two sigma bonds, it is sp hybridized; if it forms three sigma bonds, it is sp\u00b2 hybridized; and if it forms four sigma bonds, it is sp\u00b3 hybridized.

Why (B) is correct:

First, let's determine the hybridization of carbon in the combustion product, carbon dioxide (${\mathrm{CO}}_2$).

• In ${\mathrm{CO}}_2$, the central carbon atom forms two double bonds with two oxygen atoms. Each double bond consists of one sigma ($\sigma$) bond and one pi ($\pi$) bond.
• Therefore, the carbon atom in ${\mathrm{CO}}_2$ forms two sigma bonds and has no lone pairs.
• According to VSEPR theory, a central atom with two sigma bonds and no lone pairs is sp hybridized.

Now, let's analyze the hybridization of carbon in each given option:

• A) Ethane (${\mathrm{C}}_2{\mathrm{H}}_6$): Each carbon atom in ethane forms four single bonds (three with hydrogen and one with the other carbon). Thus, each carbon is sp\u00b3 hybridized.
• B) Ethyne (${\mathrm{C}}_2{\mathrm{H}}_2$): Each carbon atom in ethyne forms one triple bond with the other carbon and one single bond with hydrogen. A triple bond consists of one sigma bond and two pi bonds. Therefore, each carbon atom forms two sigma bonds (one with C and one with H) and has no lone pairs. Thus, each carbon is sp hybridized.
• C) Ethene (${\mathrm{C}}_2{\mathrm{H}}_4$): Each carbon atom in ethene forms one double bond with the other carbon and two single bonds with hydrogen. A double bond consists of one sigma bond and one pi bond. Therefore, each carbon atom forms three sigma bonds (one with C and two with H) and has no lone pairs. Thus, each carbon is sp\u00b2 hybridized.
• D) Ethanol (${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{OH}$): The first carbon (${\mathrm{CH}}_3$) forms four single bonds, so it is sp\u00b3 hybridized. The second carbon (${\mathrm{CH}}_2$) forms four single bonds (two with H, one with C, one with O), so it is also sp\u00b3 hybridized.

Comparing the hybridization, only ethyne has sp hybridized carbon atoms, which is the same as the carbon atom in ${\mathrm{CO}}_2$.

Correct Answer: (B)