Bayer's process is used for the purification of Bauxite containing which of the following as an impurity?

Which of the following is not concentrated by electromagnetic separation?

In the Serpek process for the purification of bauxite,what is used to remove silicon dioxide?

What is concentration of ore?

In the leaching of alumina from bauxite,the ore impurity expected to leach out in the process by reacting with $NaOH$ is:

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.