Whire phosphorous on reaction with lime water gives calcium...

Whire phosphorous on reaction with lime water gives calcium salt of an acid (P) along with a gas (Q). Which of the following is correct? (a) $(Q)$ is more basic than ammonia. (b) (P) is dibasic acid (c) 'The bond angle in (Q) is less than that in case of ammonia. (d) ( $\mathrm{P}$ ) on heating gives (Q) and $\mathrm{O}_{2}$.

Whire phosphorous on reaction with lime water gives calcium salt of an acid (P) along with a gas
(Q). Which of the following is correct?
(a) $(Q)$ is more basic than ammonia.
(b) (P) is dibasic acid
(c) 'The bond angle in (Q) is less than that in case of ammonia.
(d) ( $\mathrm{P}$ ) on heating gives (Q) and $\mathrm{O}_{2}$.

Key Concepts

Basicity Comparison Between Phosphine and Ammonia

The basicity of a molecule is influenced by the electronegativity and the availability of a lone pair for bonding. Phosphine (PH3) is significantly less basic than ammonia (NH3) because phosphorus is less electronegative than nitrogen, leading to a less effective donation of its lone pair. This difference is a classic illustration of how periodic trends affect chemical reactivity and strength of bases.

Molecular Geometry and Bond Angle Comparisons

The shape and bond angles of molecules depend on the central atom’s size, bonding, and lone pair repulsion. In comparing trigonal pyramidal molecules like phosphine (PH3) and ammonia (NH3), differences in bond angles arise because PH3 exhibits a smaller bond angle due to poorer orbital hybridization and less effective lone pair–bond pair repulsion relative to the more tightly held electrons in ammonia.

Hypophosphorous Acid Structure and Acidity

Hypophosphorous acid (commonly H3PO2) is notable for being monobasic despite having three hydrogen atoms because only one hydrogen, which is attached to an oxygen atom, is acidic. This concept is essential in understanding acid strength and behavior, emphasizing that the number of hydrogen atoms does not always correspond to basicity or titratable protons.

Reaction of White Phosphorus in Alkaline Media

White phosphorus reacts with bases or alkaline solutions to produce phosphorus-containing compounds such as phosphine (PH3) along with salts of phosphorus acids. This reaction is an important example in inorganic chemistry where the conditions lead to redox processes, forming reduced phosphorus species as the gas and oxidized phosphorus as part of an acid salt.

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