Which of the following statements are correct? I ) P 4 molecule is very reactive because of angular strain. II ) The basicity of H 3 PO 3 is 3 . III ) In gas phase, all P - Cl   bonds of PCl 5 have same bond length. IV ) In solid state, PCl 5 exists as an ionic solid, in which anion PCl 6 - has octahedral and cation PCl 4 + has tetrahedral shape.

Step-by-step solution

1 ) P 4 has tetrahedral unit where four P atoms are arranged in the four corners of a tetrahedron joined together by a total of six single bonds i.e each P atom makes bond with 3 other P atoms to complete its octet leading to reorientation of orbitals thus resulting in a bond angle of 60 ° . 2 ) Basicity of H 3 PO 3 = 2 3 ) PCl 5 has trigonal bipyramidal structure, three equatorial P – Cl   bonds are equatorial, while the two axial bonds are longer than equatorial bonds. 4 ) In solid state, PCl 5 ex