NEET Chemistry The p-Block Elements (XII) Questions Solved


Account for the following :

(a) Thermal stability of water is much higher than that of H2S.

(b) White phosphorus is more reactive than red phosphorus.

(c) Ammonia acts as a ligand.

(d) Bismuth is a strong oxidizing agent in pentavalent state.

(e) Concentrated sulphuric acid is a strong dehydrating agent.

(a) The thermal stability of hydrides decrease from H2O to H2S because as the size of the atom increases, the bond becomes weaker and thus breaks on heating.

(b) Red phosphorus is regarded as a polymer consisting of chains of P4 tetrahedral linked together. This makes phosphorus denser and less reactive

But in white phosphorus P4, the four phosphorus atoms lie at the corners of a regular tetrahedron. Each phosphorus atom is linked to each of the other three atoms by covalent bond. The bond angle is equal to 60° which suggests that the molecule is under strain and hence active in nature.

(c) Due to the presence of a lone pair of electrons on nitrogen atom, it has a tendency to donate an electron pair, hence acts as a ligand.

(d) In Bismuth, the inert pair effect is very prominent. Thus +5 oxidation state is less stable in comparison to +3 oxidation state i.e. it readily accepts two electrons in pentavalent state and gets reduced to trivalent state. Therefore, it acts as a strong oxidising agent.

(e) Conc. H2SO4 has great affinity for water molecule i.e. it acts as a dehydrating agent.

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