Q2. Why is N-O bond shorter than N-O-H bond in HNO3 molecule?
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.
As we can see from the resonating structures, there is double bon 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.
And 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.
Hope it helps!