NEET Practice Questions (MCQs) with Answers & Solutions

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, 'Active immunity is slow and takes time to give its full effective response.' Options o1 and o2 describe passive immunity, and o4 is an example of passive immunity.

The NCERT states, 'When ready-made antibodies are directly given to protect the body against foreign agents, it is called passive immunity.' Anti-venom contains pre-formed antibodies, so it's a classic example of passive immunity.

The NCERT states, 'infectious organisms gaining access into body during natural infection induce active immunity.' Options o1 and o2 are explicitly mentioned as examples of passive immunity in the text, and o4 describes the direct administration of antibodies, which is passive immunity.

Vaccination involves introducing antigenic proteins or inactivated/weakened pathogens (foreign agents) into the body to stimulate antibody production by the host, which is active immunity. Since it's deliberately induced, it's artificially acquired. The text states, 'Injecting the microbes deliberately during immunisation... induce active immunity'.

The NCERT explicitly mentions, 'The yellowish fluid colostrum secreted by mother during the initial days of lactation has abundant antibodies (IgA) to protect the infant.'

Active immunity is defined by the host producing its own antibodies when exposed to antigens. The text states, 'When a host is exposed to antigens... antibodies are produced in the host body. This type of immunity is called active immunity.' Passive immunity provides immediate protection and involves pre-formed antibodies (not memory).