(a)Account for the following :
(i)The acidic strength decreases in the order `HCl gt H_(2)S gt PH_(3)`
(ii)Tendency to form pentahalides decreases down the group in group 15 of the periodic table.
(b)Complete the following chemical equations. :
(i)`P_(4)+SO_(2)Cl_(2)to`
(ii)`XeF_(2)+H_(2)O to`
(iii)`I_(2)+underset(("conc"))(HNO_(3)) to`

Answer

(a)(i)HCl is stronger acid than HF.The acid strength of hydrogen halide is `HFltHClltHBrltHI`.
(ii)Element of this group form both ionic and covalent compounds in +3 oxidation state.In net shell, the covalent character decreases in the order :
`NgtPgtAsgtSbgtBi`.
Due to inert pair effect.
(b)(i)`P_(4)+10 SO_(2)Cl_(2)tounderset("Phosphorus pentachloride")(4PCl_(5)+10 SO_(2))`
(ii)`2XeF_(2)+H_(2)Oto2Xe+4HF+O_(2)`
(iii)underset(("conc."))(`I_(2)+10HNO_(3))tounderset("Iodine to Iodine acid")(2HIO_(3)+10NO_(2)+)4H_(2)O`