Aluminium is extracted from alumina Al2O3 by electrolysis of a molten mixture of:
1.
2.
3.
4.
The correct statement among the following is:
1. | The rate of reaction cannot be understood from the Ellingham diagram. |
2. | During the formation of metal oxide \(\Delta S\) becomes negative and \(\Delta G\) becomes positive resulting in a positive slope. |
3. | There is an abrupt change in the slope of the Ellingham line when a change in phase (s→l) or (l→g) takes place. |
4. | All of the above. |
Which metal can be purified by zone refining?
1. Ni
2. Zr
3. In
4. Fe
The chemical composition of "slag" formed during the smelting process in the extraction of copper is:
1. Cu2 + FeS
2. FeSiO3
3. CuFeS
4. Cu2S + FeO
The correct statement among the following is:
1. | In the decomposition of oxide into oxygen and gaseous metal, entropy increases. |
2. | Decomposition of oxide is an endothermic change. |
3. | To make ∆G° negative, the temperature should be high enough so that T∆S° > ∆H°. |
4. | All of the above. |
The fundamental principle of froth flotation process is:
1. | Impurities and metal ore have different wetting properties. |
2. | Impurities and metal ore have different solubility. |
3. | Impurities and metal ore have different diversity. |
4. | Impurities and metal ore have different compressive powers. |
Ellingham's diagram for the formation of is a straight line in the given graph.
This is due to:
1. Increase in entropy during formation.
2. Decrease in entropy during formation.
3. Entropy remains constant during formation.
4. Can not be predicted.
Consider the following reactions at 1000 oC.
(I) ZnS + 1/2O2(g) \(\xrightarrow[]{\Delta }\) ZnO(g); ∆Go = -360 kJ mol-1
(II) Cs + 1/2O2(g) \(\xrightarrow[]{\Delta }\) CO(g); ∆Go = -460 kJ mol-1
Choose the correct statement about the above reactions at 1000 oC:
1. ZnO is more stable than CO
2. ZnO can be reduced to Zn by C
3. ZnO, and CO are formed at an equal rate
4. ZnO can not be reduced to Zn by C
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.