The complex formed when $Al_2O_3$ is leached from Bauxite using concentrated $NaOH$ solution is,

Leaching of $Ag_2S$ is carried out by heating it with a dilute solution of

Which of the following ores can be concentrated by the froth flotation method?

Sulphide ores of metals are usually concentrated by froth floatation process. Which one of the following sulphide ores offers an exception and is concentrated by chemical leaching?

The correct statements regarding the froth floatation method in metallurgy are:
$I$. Used for the purification of sulphide ores
$II$. Used for the roasting of sulphide ores
$III$. It is based on the relative densities of gangue and ore particles
$IV$. It is based on the difference in the wetting properties of gangue and ore particles in frothing agent and water

The substance added to the ore to remove impurities is known as........