Aluminium chloride exists as dimer, $Al_2Cl_6$ in solid state as well as in soluiton of non-polar solvents such as $C_6H_6.$ When dissolved in water it gives :

$B{X_3} + N{H_3}\xrightarrow{{R.T}}B{X_3}.N{H_3} + Heat\,of\,adduct\,formation\,\left( {\Delta H} \right)$ The numerical value of $\Delta H$ is found to be maximum for

Which among the following statement(s) is(are) true for the extraction of aluminium from bauxite?

$(A)$ Hydrated $Al _2 O _3$ precipitates, when $CO _2$ is bubbled through a solution of sodium aluminate.

$(B)$ Addition of $Na _3 AlF _6$ lowers the melting point of alumina.

$(C)$ $CO _2$ is evolved at the anode during electrolysis.

$(D)$ The cathode is a steel vessel with a lining of carbon.

A layer of coke is spread over bauxite during electrolytic reduction of alumina by Hall-Heroult process. This layer acts as a/an:

In $B_2H_6$