D & F Block Elements MCQs for NEET — Chemistry Questions with Answers

The text states regarding actinoids: 'However, even the early actinoids resemble the lanthanoids in showing close similarities with each other and in gradual variation in properties which do not entail change in oxidation state.' This indicates a commonality in this specific aspect for the early actinoids resembling lanthanoids.

The text states: 'The action of boiling water on them, for example, gives a mixture of oxide and hydride...'

The text states: 'The magnetic properties of the actinoids are more complex than those of the lanthanoids.' (So I is incorrect). 'Although the variation in the magnetic susceptibility of the actinoids with the number of unpaired 5f electrons is roughly parallel to the corresponding results for the lanthanoids, the latter have higher values.' (So II and III are correct).

The text states: 'The actinoids show in general +3 oxidation state.' and also 'The actinoids resemble the lanthanoids in having more compounds in +3 state than in the +4 state.'

The text states: 'Because the distribution of oxidation states among the actinoids is so uneven and so different for the former and later elements, it is unsatisfactory to review their chemistry in terms of oxidation states.'

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).'