In the concentration of $PbS$ containing $ZnS$ as impurity,the depressant used is:

If bauxite contains $SiO_2$ as an impurity,which of the following methods can be used for its purification?

The function of potassium ethyl xanthate in the froth floatation process is to make the ore

Observe the following statements regarding the purification of bauxite and select the correct answer.
$(I)$ During the $Hall$ process,silicon is removed in the form of vapor.
$(II)$ Bauxite containing $Fe_2O_3$ impurities is purified by the $Bayer$ process.
$(III)$ $AlN$ is formed during the $Serpeck$ process.

In the cyanide process for extraction of gold and silver from ores,the cyanide solution acts as a

For the purification of alumina,the modern processes most useful when $(i)$ the impurity present is a lot of iron oxides and $(ii)$ the impurity present is a lot of silica,are: