What happens in the extraction of chlorine by electrolysis of brine?

1. Oxidation of $C{l}^{-}$ ion to chlorine gas occurs.

2. Reduction of $C{l}^{-}$ ion to chlorine gas occurs.

3. For overall reaction $∆\mathrm{G}°$has negative value.

4. A displacement reaction takes place.

What does copper matte contain?

1. Sulphides of copper(I), and iron(II)

2. Sulphides of copper (II), and iron(III)

3. Sulphides of copper(II), and iron(II)

4. Sulphides of copper(I), and iron(III)

Which of the following reactions is an example of autoreduction?

$1. {\mathrm{Fe}}_3{\mathrm{O}}_4+ 4\mathrm{CO}\to 3\mathrm{Fe}+ 4{\mathrm{CO}}_2$

$2. {\mathrm{Cu}}_2\mathrm{O}+ \mathrm{C}\to 2\mathrm{Cu}+ \mathrm{CO}$

$3. {\mathrm{Cu}}^{2+}\left(\mathrm{aq}\right) + \mathrm{Fe}\left(\mathrm{s}\right) \to \mathrm{Cu}\left(\mathrm{s}\right) +{\mathrm{Fe}}^{2+}\left(\mathrm{aq}\right)$

$4. {\mathrm{Cu}}_2\mathrm{O}+\frac{1}{2}{\mathrm{Cu}}_2\mathrm{S}\to 3\mathrm{Cu}+\frac{1}{2}{\mathrm{SO}}_2$

Which are the most abundant elements present inside the earth's crust?

1. Al, and Fe 

2. Al, and Cu

3. Fe, and Cu

4. Cu, and Ag

Zone refining is based on the principle that-

In the extraction of copper from its sulphide ore, the metal is formed by the reduction of ${\mathrm{Cu}}_2\mathrm{S}$ with :
1. $\mathrm{FeS}$   
2. $\mathrm{CO}$
3. $C{u}_{2}O$   
4. ${\mathrm{SO}}_2$

Brine is electrolysed by using inert electrodes. The reaction at the anode is:

1. Cl^-(aq) → \(\frac{1}{2}\)Cl₂(g) + e^-;  \(E_{cell}^{o}\) = 1.36 V

2. 2H₂O(l) → O₂(g) + 4H⁺ +  4 e^-;  \(E_{cell}^{o}\) = 1.23 V

3. Na⁺(aq) + e^- → Na(s); \(E_{cell}^{o}\) = 2.71 V

4. H⁺(aq) + e^- → \(\frac{1}{2}\)H₂(g); \(E_{cell}^{o}\) = 0.00 V

In the metallurgy of aluminium:

Which of the following metals can be purified by electrolytic refining?

1. Cu, and Zn     

2. Ge, and Si     

3. Zr, and Ti     

4. Zn, and Hg

Extraction of gold and silver involves leaching the metal with $C{N}^{-}$ ion. The metal is recovered by ......