A pair of metals among the following that can be purified by the van Arkel method are:

1. Zr,  and Ti

2. Ag, and Au

3. Ni,  and Fe

4. Ga, and In

4M + 8CN^- + 2H₂O + O₂$\to$ 4[M(CN)₂]^- + 4OH^-

2[M(CN)₂]^- + Zn$\to$[Zn(CN)₄]^2- + 2M

The metal M in above-mentioned reaction is:

1. Nickel

2. Silver

3. Copper

4. Mercury

The extraction of gold and silver involves leaching with CN^- ion. Silver is later recovered by:

1. Liquation

2. Distillation

3. Zone refining

4. Displacement with Zn

A major impurity in pig iron is:

1. Carbon

2. Silicon

3. Phosphorus

4. Manganese

In the extraction of aluminium by the Hall-Heroult process, purified ${\mathrm{Al}}_2{\mathrm{O}}_3$ is mixed with ${\mathrm{CaF}}_2$ to:

Choose the correct option:
1. a and b
2. b and c
3. c and d
4. a and d

Aluminium is extracted from alumina Al₂O₃ by electrolysis of a molten mixture of:

1. ${\mathrm{Al}}_2{\mathrm{O}}_3+\mathrm{HF}+{\mathrm{NaAlF}}_4$

2. ${\mathrm{Al}}_2{\mathrm{O}}_3+{\mathrm{CaF}}_2+{\mathrm{NaAlF}}_4$

3. ${\mathrm{Al}}_2{\mathrm{O}}_3+{\mathrm{Na}}_3{\mathrm{AlF}}_6+{\mathrm{CaF}}_2$

4. ${\mathrm{Al}}_2{\mathrm{O}}_3+\mathrm{KF}+{\mathrm{Na}}_3{\mathrm{AlF}}_6$

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

The common impurities present in bauxite are:

a. $\mathrm{CuO}$                    

b. $\mathrm{ZnO}$                

c. ${\mathrm{Fe}}_2{\mathrm{O}}_3$                

d. ${\mathrm{SiO}}_2$

Choose the correct option:
1. a and b
2. b and c
3. c and d
4. a and d

The correct match among the following is: