Chemistry MCQs for NEET — Practice Questions with Answers

The NCERT defines it as: 'The energy of actual structure of the molecule (the resonance hybrid) is lower than that of any of the canonical structures. The difference in energy between the actual structure and the lowest energy resonance structure is called the resonance stabilisation energy or simply the resonance energy.'

The NCERT states, 'Among the resonance structures, the one which has more number of covalent bonds, all the atoms with octet of electrons (except hydrogen which has a duplet), less separation of opposite charges, (a negative charge if any on more electronegative atom, a positive charge if any on more electropositive atom) and more dispersal of charge, is more stable than others.'

The NCERT states, 'Resonance averages the bond characteristics as a whole.'

The statement 'The cannonical forms have no real existence' followed by 'The molecule does not exist for a certain fraction of time in one cannonical form and for other fractions of time in other cannonical forms' implies that canonical forms are not actual structures that the molecule adopts, but rather theoretical representations that collectively describe the true structure (the resonance hybrid).

According to the NCERT text, 'Allylic alcohols: In these alcohols, the —OH group is attached to a $sp^3$ hybridised carbon adjacent to the carbon-carbon double bond, that is to an allylic carbon.'

The NCERT states, 'Ethers are classified as simple or symmetrical, if the alkyl or aryl groups attached to the oxygen atom are the same, and mixed or unsymmetrical, if the two groups are different. Diethyl ether, $C_2H_5OC_2H_5$, is a symmetrical ether whereas $C_2H_5OCH_3$ and $C_2H_5OC_6H_5$ are unsymmetrical ethers.' In option o3 ($C_2H_5OCH_3$), the two alkyl groups attached to the oxygen (ethyl and methyl) are different, making it an unsymmetrical ether.

The NCERT states, 'Alcohols and phenols may be classified as mono–, di–, tri- or polyhydric compounds depending on whether they contain one, two, three or many hydroxyl groups respectively in their structures'.

According to the NCERT Table 7.1, the common name 'm-Cresol' corresponds to the IUPAC name '3-Methylphenol'.

The NCERT Summary states, 'Ethers are classified on the basis of groups attached to the oxygen atom.'

The NCERT text classifies primary, secondary, and tertiary alcohols based on whether the -OH group is attached to a primary, secondary, or tertiary carbon atom, respectively. A primary carbon is bonded to one or no other carbon atoms.