In the extraction of silver from the argentite ore, the ore is treated with a dilute solution of $\mathrm{NaCN}$ in water, in the presence of $\mathrm{Y}$. Whereby the following reaction takes place:
${\mathrm{Ag}}_2\mathrm{X}+4\mathrm{NaCN}+2\mathrm{Y}\to 2\mathrm{Na}\left[\mathrm{Ag}(\mathrm{CN}{)}_2\right]+{\mathrm{Na}}_2{\mathrm{XO}}_4$. $\mathrm{X}$ and $\mathrm{Y}$ in this reaction are 

How many of the following metals can be extracted by auto-reduction?

 $\mathrm{Fe}, \mathrm{Zn}, \mathrm{Pb}, \mathrm{Al}, \mathrm{Hg}, \mathrm{Cu}, \mathrm{K}, \mathrm{Ca}$ .

There are many minerals of zinc present in nature and some of this are - Zinc blende, willemite, franklinite, zincite and calamine . One of these minerals of zinc contains metal, nonmetal and metalloid elements in its chemical formula. The total number of atoms present per molecule in this mineral is_____.

The total number of oxide minerals of iron in the following are - 

Haematite, iron pyrites, siderite, magnetite, limonite

How many of the following are methods to concentrate ores?

Gravity separation, magnetic separation, chromatography, froth floatation process, polling