Chemistry MCQs for NEET — Practice Questions with Answers

The text mentions: 'Chlorine containing antibiotic, chloramphenicol, produced by microorganisms is very effective for the treatment of typhoid fever.'

The text states: 'These may be classified as mono, di, or polyhalogen (tri-,tetra-, etc.) compounds depending on whether they contain one, two or more halogen atoms in their structures.'

The text states: 'The boiling points of organohalogen compounds are comparatively higher than the corresponding hydrocarbons because of strong dipole-dipole and van der Waals forces of attraction.'

The text says: 'Certain fully fluorinated compounds are being considered as potential blood substitutes in surgery.'

The text states: 'Halogenated compounds persist in the environment due to their resistance to breakdown by soil bacteria.'

The contraction is, however, greater from element to element in this series resulting from poor shielding by 5f electrons. The statement that actinoid contraction is more significant than lanthanoid contraction due to more effective shielding by 5f electrons is incorrect. The context states that 'The contraction is, however, greater from element to element in this series resulting from poor shielding by 5f electrons.' This implies that poor shielding, not effective shielding, is the cause, and while the contraction per element is greater, the overall significance is often attributed to lanthanoid contraction's impact on subsequent elements, as stated: 'The lanthanoid contraction is more important because...'

The text states: 'The irregularities in the electronic configurations of the actinoids, like those in the lanthanoids are related to the stabilities of the $f^0$, $f^7$ and $f^{14}$ occupancies of the 5f orbitals. Thus, the configurations of Am and Cm are [Rn] $5f^7 7s^2$ and [Rn] $5f^7 6d^1 7s^2$.' Americium (Am) clearly shows a $5f^7$ configuration, indicating stability due to a half-filled orbital.

The text states: 'There is a greater range of oxidation states, which is in part attributed to the fact that the 5f, 6d and 7s levels are of comparable energies.' This allows for the participation of more electrons in bonding.

The text states: 'Hydrochloric acid attacks all metals but most are slightly affected by nitric acid owing to the formation of protective oxide layers; alkalies have no action.' Thus, hydrochloric acid attacks all actinoid metals.

The text states: 'The fourteen electrons are formally added to 5f, though not in thorium (Z = 90) but from Pa onwards the 5f orbitals are complete at element 103.' This clearly indicates that thorium (Th) does not have 5f orbital occupancy in its ground state configuration as explained here.