AlF₃ is soluble in HF only in presence of KF. It is due to the formation of

1.  ${\mathrm{K}}_3\left({\mathrm{AIF}}_3{\mathrm{H}}_3\right)$

2.  ${\mathrm{K}}_3\left({\mathrm{AIF}}_6\right)$

3.  ${\mathrm{AIH}}_3$

4.  $\mathrm{K}\left({\mathrm{AIF}}_3\mathrm{H}\right)$

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

1. Distillation

2. Zone refining

3. Displacement with Zn

4. Liquation

Considering Ellingham diagram, which of the following metals can be used to reduce alumina?

1. Fe.

2. Zn

3. Mg

4. Cu

The correct match among the following is-

1. A-2, B-3, C-1, D-4

2. A-1, B-2, C-3, D-4

3. A-3, B-4, C-2, D-1

4. A-4, B-2, C-3, D-1

Among the following an iron mineral is:

1. Malachite

2. Cassiterite

3. Pyrolusite

4. Magnetite

A major impurity in pig iron is:

1. Carbon

2. Silicon

3. Phosphorus

4. Manganese

Which of the following statements, about the advantage of roasting of sulphide ore before reduction is not true?

1. Carbon and hydrogen suitable reducing agents for metal sulphides

2. The ${∆}_f{G}^0$ of the sulphide is greater than those for $C{S}_2$ and $H_{2}S$

3. the ${∆}_f{G}^0$ is negative for roasting of sulphur ore to oxide.

4. Roasting of the sulphide to the oxide is thermodynamically feasible

Sulphide ores of metals are usually concentrated by froth flotation process. Which one of the following sulphide ores offers an exception and is concentrated by chemical leaching?

1. Argentite

2. Galena

3. Copper pyrite

4. Sphalerite

Identify the incorrect statement

In the conversion of Zinc ore to zinc metal, the process of roasting involves

1.  ${\mathrm{ZnCO}}_3 \stackrel{}{\to } \mathrm{ZnO}$

2.  $\mathrm{ZnO} \stackrel{}{\to } {\mathrm{ZnSO}}_4$

3.  $\mathrm{ZnS} \stackrel{}{\to } \mathrm{ZnO}$

4.  $\mathrm{ZnS} \stackrel{}{\to } {\mathrm{ZnSO}}_4$