An ore of tin containing $FeCrO_4$ is concentrated by

Which principle is involved in froth flotation?

Which of the following is used as a stabilizer during the concentration of sulphide ores?

In the froth-floatation process,palm oil functions as:

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.

Which soluble substances are obtained when bauxite is treated with a solution of $NaOH$ at a temperature of $473 - 523 \ K$ and a pressure of $35 - 36 \ bar$?