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WHY? 1.NH3 is a strong base than PH3. 2. in the structure of HNO3, the N-O bond is shorter than the N-OH bond 3.all the P-Cl bond in PCl5 are not equivalent 4. NH3 is good complexing agent

1. By definition from Lewis, a base is an electron pair donor.Due to smaller atomic size the density of lone pair electrons on N in NH3 is larger than that of P in PH3. So, NH3 is a stronger Lewis base than that of PH3.

2.N-O bond is shorter than N-OH bond in HNO3 molecule. It can be understood with the help of resonating structures of HNO3 molecule.There is double bond character between N-O bonds but there is always single bond character between N-OH bond. This is because of no pi-bonding occurring between nitrogen and oxygen of OH group.We know that double bond is shorter than single bond. So we can say that N-O bond is shorter than N-OH bond in HNO3 molecule.

3.There are two bonds in PCl5 .One is Equatorial and other is Axial and because of the repulsion factor one is longer and the other shorter.The bond nature is trigonal bipyramid. Two axial bonds of same length are at angle 90. Three equatorial bonds of same length are at bond angle of 120.This is due to the minimum repulsion of charge between the Cl atoms.

4.Ammonia is a good complexing agent because it is a good lewis base. More is the tendency of an atom, molecule or ion to donate electrons, more is its ability to form a complex. There is a lone pair of electrons present on nitrogen in ammonia, which it can donate readily to the central metal atom and hence forms a complex with it.

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