Chemistry MCQs for NEET — Practice Questions with Answers

The context states: '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 context states: 'The resonance structures have (i) the same positions of nuclei and (ii) the same number of unpaired electrons.' It also says: 'They contribute to the actual structure in proportion to their stability,' which implies they are not necessarily equally stable (some are more stable contributors than others). For example, in Problem 8.17, stability I > II > III is clearly mentioned.

The context states: 'however, it is known that the two N–O bonds of nitromethane are of the same length (intermediate between a N–O single bond and a N=O double bond). The actual structure of nitromethane is therefore a resonance hybrid of the two canonical forms I and II.'

The context states: 'Resonance stabilizes the molecule as the energy of the resonance hybrid is less than the energy of any single canonical structure.'

The context states: 'This effect is observed when the transfer of electrons is towards the atom or substituent group attached to the conjugated system. For example in nitrobenzene this electron...'

The context states: 'The transition metals and their compounds are known for their catalytic activity. This activity is ascribed to their ability to adopt multiple oxidation states and to form complexes.'

The context mentions: 'finely divided iron (in Haber’s Process)' as an example of a transition metal catalyst.

The context specifies: 'Vanadium(V) oxide (in Contact Process)' as a catalytic agent.

The context states: 'They have high melting points, higher than those of pure metals.' Therefore, the statement that they have lower melting points is incorrect.

The context explains: 'Catalysts at a solid surface involve the formation of bonds between reactant molecules and atoms of the surface of the catalyst... This has the effect of increasing the concentration of the reactants at the catalyst surface and also weakening of the bonds in the reacting molecules (the activation energy is lowering).'