NEET Practice Questions (MCQs) with Answers & Solutions

Cyclic metaphosphoric acid ( ext{HPO}_3)_n contains three ext{P-O-P} bonds in its ring structure. The structure can be represented as a cyclic trimer with the formula ( ext{HPO}_3)_3. Each phosphorus atom is bonded to two oxygen atoms, which in turn are bonded to two different phosphorus atoms, creating three ext{P-O-P} linkages.

$ (NH_4)2SO_4 + KCNO \rightarrow NH_4CNO + K_2SO_4 \rightarrow NH_2CONH_2 urea $

Ammonia generally prepared by Haber's process

One part conc. $ HNO_3$ & 3parts conc. HCl forms aquaregia.

The stability of hydrides of group 15 elements decreases down the group. This is due to the decreasing bond strength and increasing size of the central atom. Hence, $SbH_3$ (Antimony hydride) is the least stable among the given options.

$NH_3$ (Ammonia) is the most stable hydride among the given options. This is because nitrogen has a smaller size and higher electronegativity, leading to stronger N-H bonds and better hydrogen bonding compared to other group 15 hydrides.

The boiling point of hydrides of group 15 elements increases down the group due to increasing molecular weight and van der Waals forces. However, $NH_3$ has an anomalously high boiling point due to strong hydrogen bonding. Hence, $PH_3$ (Phosphine) has the lowest boiling point among the given options.

Nitrogen trichloride ( ext{NCl}_3) is the most explosive among the given options. It is highly sensitive to heat, shock, and organic matter, and can decompose violently. This is because it forms nitrogen gas ( ext{N}_2) and chlorine gas ( ext{Cl}_2) upon decomposition, releasing a significant amount of energy.

Phosphorus trioxide ( ext{P}_2 ext{O}_3) is the most acidic among the given options. This is because it reacts with water to form phosphorous acid ( ext{H}_3 ext{PO}_3), which is a stronger acid compared to the acids formed by the other given oxides.