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 :

The unit cell of copper corresponds to a face centered cube of edge length 3.596 $$\mathop A\limits^o $$ with one copper atom at each lattice point. The calculated density of copper in kg/m³ is ___________. [Molar mass of Cu : 63.54 g; Avogadro Number = 6.022 $$\times$$ 10²³]