(a) Explain the following :
(i) `NF_3` is an exothermic compound whereas `NCl_3` is not.
(ii) `F_2` is most reactive of all the four common halogens.
(b) Complete the following chemical equations:
(i) ` C +H_2SO_4("conc")to`
(ii) `P_A+NaOH+H_2Oto`
(iii) `{:(Cl_2+F_2to),(("excess")):}`

Explanation

(a)(i) `NF_(3)` is an exothermic compound whereas `NCl_(3)` is endothermic compound because bond energy of `F_(2)`is lower than `Cl_(2)` and N-F bond is smaller and stronger than N-Cl bond.
(ii) Because of the lower bond energy of F-F bond and higher energy of `F^(-)` ions, flourine is the strongest oxidant amongest the halogens.
(b) (i) `C+2H_(2)SO_(4)"(conc.)"to 2SO_(2)+underset("carbon dioxide")(CO_(2)+2H_(2)O)`
(ii) `P_(4)+3NaOH+3H_(2)underset("Phosphine")(O to PH)+ underset("sodium hypophosphite")(3NaH_(2)PO_(2))`
(iii) `underset(("excess"))(CI_(2)+3F_(2))overset(heat)to2 CIF_(3)`