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 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
Incorrect statement for the Hall-Heroult process is:
1. | Cryolite Na3AlF6 lower the melting point of Al2O3, and increase its electrical conductivity. |
2. | Al is obtained at the cathode, and CO2 at the anode. |
3. | Li2CO3 can be used in place of cryolite(Na3AIF6) |
4. | MgF2 can be used in place of fluorspar (CaF2) |
What is the composition of the anode mud used in the electrolytic refining of silver?
1. Zn, Cu, Ag, Au
2. Zn, Ag, Au
3. Cu, Ag, Au
4. Au only
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
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
During extraction, copper is obtained by the reduction of cupric oxide with:
1. Cu2S
2. SO2
3. FeS
4. CO
Aluminium is extracted from alumina Al2O3 by electrolysis of a molten mixture of:
1.
2.
3.
4.
Which of the following has a negative slope?
1. C CO
2. Fe Fe2O3
3. Mg MgO
4. All of the above
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. |