(a) (i) Complete the following chemical equations :
(i)`NaOH_((aq))+Cl_(2(g)) rightarrow`
(Hot and conc.)
(ii) `Xef_(6)(s)+H_(2)O(l) rightarrow`
(b) How would you account for the following ?
(i) The value of electron gain enthalpy with negative sign for sulphur is higher than that for oxygen.
(ii) `NF_(3)` is an exothermic compound but `NCl_(3)` is endothermic compound.
(iii)`ClF_(3)` molecule has a T-shaped structure and not a trigonal planar one.

Answer

(i)It is due to higher lattice energy of oxides as compared to fluorides as oxide ion is dinegative whereas fluoride ion is mononegative.
(ii)It is because Xe is noble gas and has lone pair of electrons in its d-orbitals.Size of 5d orbitals in Xe is large enough for effective overlapping. 5p and 5d orbitals of Xe differ by `960 kh mol^(-1)`, that in `sp^(3)d` hybridisation, contribution of 5d orbital is objectionable.
(a)(i)`6NaOH_(aq) + 3Cl_(2)(g)to5NaCl + NaClO_(3) + 3H_(2)O`
(ii)`overset(("Hot and conc."))(XeF_(6)(s))+3H_(2)O_(l)toXeO_(3) + 6HF`
(b)(i)The negative electron gain enthalpies are large for elements of group 16.However, the atomic size of oxygen is quite small.Because of this, the electron-electron repulsions in 2p sub-shell are quite high.Hence, the incoming electron is not accepted as easily in oxygen as it in sulphur.Hence, the negative electron gain enthalpy for sulphur is higher than of oxygen.
(ii)The instability of `NCl_(3)` is due to the weak `NCl` bond.This is due to the large difference in the size of nitrogen and chlorine atoms.On the other hand, atoms of both nitrogen (75 pm) and fluorine (72 pm) are small sized.Thus, bonding in `NF_(3)` is quite strong and it is an exothermic compound.
(iii)`CIF_(3)` molecule involves a `sp^(3)d` hybridization of the central atom 'Cl'
`(##RES_INO_CHM_XII_V02_C03_E01_178_A01##)`
Thus, `CIF_(3)` have trigonal bipyramidal geometries with two positions occupied by 2 lone pairs. Hence it is T-shaped.