The role of depressant in froth floatation process is :

The extraction of copper from pyrites is more difficult than from its oxide ores through reduction because -

1.  $∆{\mathrm{G}}_{\mathrm{f}}$ of HCl is less than that of ${\mathrm{H}}_2\mathrm{S}<mspace\; width="1em"></mspace>\mathrm{and}<mspace\; width="1em"></mspace>{\mathrm{CS}}_2$

2. $∆{\mathrm{G}}_{\mathrm{f}}$ of HNO₃ is less than that of ${\mathrm{H}}_2\mathrm{S}<mspace\; width="1em"></mspace>\mathrm{and}<mspace\; width="1em"></mspace>{\mathrm{CS}}_2$

3.  $∆{\mathrm{G}}_{\mathrm{f}}$ of ${\mathrm{Cu}}_2\mathrm{S}$ is less than that of ${\mathrm{H}}_2\mathrm{S}<mspace\; width="1em"></mspace>\mathrm{and}<mspace\; width="1em"></mspace>{\mathrm{CS}}_2$

4. $∆{\mathrm{G}}_{\mathrm{f}}$ of CuSO₄ is less than that of ${\mathrm{H}}_2\mathrm{S}<mspace\; width="1em"></mspace>\mathrm{and}<mspace\; width="1em"></mspace>{\mathrm{CS}}_2$

The correct statement among the following is:

Leaching of low-grade copper ores does not involve

1. Cu getting converted into Cu²⁺(aq) in acidic medium

2. Cu getting converted into Cu²⁺(aq) in basic medium

3. Cu²⁺(aq) getting reduced to Cu

4. using bacteria in the presence of air.

The process in which Cl₂ is obtained as a by-product is :

Incorrect statement(s) among the following options is/are: