Chemistry MCQs for NEET — Practice Questions with Answers

In organic chemistry, C-C bond lengths depend on the type of bond between the carbon atoms. In $C_2H_2$ (acetylene), the carbon atoms are connected by a triple bond, which is shorter than double bonds (found in $C_2H_4$) and single bonds (found in $C_2H_6$ and $C_4H_8$). Therefore, $C_2H_2$ has the shortest C-C distance.

In benzene ($C_6H_6$), each carbon is sp2 hybridized, leading to bond angles of $120^ ext{°}$. Similarly, in ethene ($C_2H_4$), the carbons are also sp2 hybridized, resulting in bond angles of $120^ ext{°}$ around each carbon atom.

The compound $ (CH_3)_3 COH $ (tert-butyl alcohol) involves carbon atoms that are all sp^3 hybridized. In this structure, each carbon forms four sigma bonds, which is characteristic of sp^3 hybridization. The central carbon is bonded to three methyl groups and one hydroxyl group, utilizing sp^3 hybrid orbitals for all its bonds.

When the hybridization state of carbon changes from $sp^3$ to $sp^2$ and finally to $sp$, the bond angles increase progressively. In $sp^3$ hybridization, the bond angles are approximately 109.5°. In $sp^2$ hybridization, the bond angles are 120°, and in $sp$ hybridization, the bond angles are 180°. This increase in bond angle is due to the increasing s-character in the hybrid orbitals.

In a homologous series, each successive member differs by a -CH2- group. The molecular weight of a -CH2- group is 14 amu (12 for carbon and 2 for hydrogen). Therefore, the difference in atomic mass units (amu) between consecutive members of a homologous series is 14.

A homologous series is a group of organic compounds that have a similar general formula, similar chemical properties, and successive members differ by a CH2 unit. Option o4 includes $CH_3COOH$ (acetic acid), $CH_3COOCH_3$ (methyl acetate), and $CH_3COOCH_2CH_3$ (ethyl acetate), which do not fit the criteria of a homologous series because they belong to different functional groups (carboxylic acid and esters).