$A$ substance which reacts with gangue to form fusible material is called:

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 froth floatation process is

Explain the froth flotation process.

The pair of oxides,which can be leached out when powdered bauxite containing certain impurities is digested with a concentrated solution of $NaOH$ at $473-523 \ K$ temperature and $35-36 \ bar$ pressure,are:

While extracting an element from its ore,the ore is ground and leached with dilute $KCN$ solution to form the soluble product potassium argentocyanide. The element is