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. |
\((i) Zr + 2I_2 \xrightarrow{870K} ZrI_4 \xrightarrow{2075K} Zr + 2I_2 \)
\((ii) Ni + 4CO \xrightarrow{330K} Ni(CO)_4 \xrightarrow{450K} \underset{(pure)}{Ni} + 4CO \)
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
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. |
NaCN is a depressant that is used:
1. | To Separate PbS from ZnS by forming a complex with PbS. |
2. | To Separate PbS from ZnS by forming a complex with ZnS. |
3. | To Form froth. |
4. | As a collector. |
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.
Why is roasting important in the iron metallurgy process?
1. | FeO gets oxidized to Fe2O3 which does not combine with acidic SiO2 |
2. | SiO2 is an acidic oxide which can combine with metallic oxides i.e. FeO, and Fe2O3 |
3. | FeO when roasted get oxidized to more basic Fe2O3 |
4. | None of the above. |