Which metal can be purified by zone refining?

1. Ni

2. Zr

3. In

4. Fe

\((i) Zr + 2I_2 \xrightarrow{870K} ZrI_4 \xrightarrow{2075K} Zr + 2I_2 \)
\((ii) Ni + 4CO \xrightarrow{330K} Ni(CO)_4 \xrightarrow{450K} \underset{(pure)}{Ni} + 4CO \)

The processes (ii) and (i) above, respectively, are  : 

1. Mond's process; Van Arkel process

2. Van Arkel process; Mond's process

3. Goldschmidt process; Mond's process

4. Mond's process; Goldschmidt process

The correct statement among the following is:  

The fundamental principle of froth flotation process is:

NaCN is a depressant that is used: 

Ellingham's diagram for the formation of ${\mathrm{CO}}_2$ is a straight line in the given graph. This is due to:

1. Increase in entropy during ${\mathrm{CO}}_2$ formation.

2. Decrease in entropy during ${\mathrm{CO}}_2$ formation.

3. Entropy remains constant during ${\mathrm{CO}}_2$ formation.

4. Can not be predicted.

Why is roasting important in the iron metallurgy process?  

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

The substance that acts as a collector in the froth flotation method is:

1. Sodium xenate.           

2. Sodium pyrophosphate.

3. Sodium nitroprusside.

4. Sodium ethyl xanthate.