Leaching of gold with dilute aqueous solution of $NaCN$ in presence of oxygen gives complex $[A]$,which on reaction with zinc forms the elemental gold and another complex $[B]$. $[A]$ and $[B],$ respectively are ...... .

Which of the following statements is not correct?
$1$. Reduction of alumina to give aluminium by magnesium is thermodynamically feasible.
$2$. The point of intersection of $Al_2O_3$ and $MgO$ curves in Ellingham diagram is below $1665 \ K$.
$3$. Use of magnesium as reducing agent in metallurgy of aluminium is economical.
$4$. Ellingham diagram represents the graphical plot of Gibbs energy vs temperature for the formation of the oxides of common metals and reducing agents.

The slag consists of molten impurities generally in the form of

Which of the following is an acidic flux?

From which of the following is silver obtained by the reaction with $Na[Ag(CN)_2]$?

Which technique is used in the manufacture of aluminium from bauxite?