Which of the following compound is added to the sodium extract before addition of silver nitrate for testing of halogens?

The major product of the following reaction is :

The correct order of bond dissociation enthalpy of halogens is :

Copper reduces NO$$_3^ - $$ into NO and NO₂ depending upon the concentration of HNO₃ in solution. (Assuming fixed [Cu²⁺] and P_NO = P_NO2), the HNO₃ concentration at which the thermodynamic tendency for reduction of NO$$_3^ - $$ into NO and NO₂ by copper is same is 10^x M. The value of 2x is _______. (Rounded off to the nearest integer)

[Given, $$E_{C{u^{2 + }}/Cu}^o = 0.34$$ V, $$E_{NO_3^ - /NO}^o = 0.96$$ V, $$E_{NO_3^ - /N{O_2}}^o = 0.79$$ V and at 298 K, $${{RT} \over F}$$(2.303) = 0.059]