(a) Complete the following chemical reaction equations :
(b) Explain the following observations giving appropriate reasons :
(i) The stability of +5 oxidation state decreases down the group in group 15 of the periodic table.
(ii) Solid phosphorus pentachloride behaves as an ionic compound.
(iii) Halogens are strong oxidizing agents.
(b) (i) Group 15 first elements are pentavalent, therefore they can show positive oxidation state +3 (due to P-electron) and +5 (due to P and S electrons). In a group the +5 oxidation state stability decreases but +3 oxidation state increases due to inter pair effect which results the 5-orbitals electrons to participate in bonding hence shows +3 oxidation state as their stable oxidation state.
(ii) conducts electricity in the molten state. This means that in solid state it exists as in which the cation is tetrahedral and the anion is octahedral.
On melting, these ions become free to move and hence conducts electricity in the molten state.
(iii) As halogens are strong electron acceptors and change to negative ions and thus undergo reduction, so they are strong oxidising agent.