The beneficiation of the sulphide ores is usually done by

Select the correct option regarding the method of separating two sulfide ores by the froth flotation process.
$(1)$ The ratio of water and oil is chosen appropriately.
$(2)$ Some depressants are used for this process.
$(3)$ $HCN$ is a depressant for a mixture of $ZnS$ and $PbS$.
$(4)$ By using a suitable depressant for a mixture of $ZnS$ and $PbS$,only $PbS$ comes up with the froth.

The ore that is concentrated by the froth floatation process is

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

What is the role of a depressant in the froth flotation process?

How can you separate alumina from silica in bauxite ore associated with silica? Give equations,if any.