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: 

Incorrect statement for the Hall-Heroult process is:

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);  ∆G^o = -360 kJ mol^-1
(II) Cs + 1/2O₂(g)  \(\xrightarrow[]{\Delta }\) CO(g); ∆G^o = -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. ${\mathrm{Al}}_2{\mathrm{O}}_3+\mathrm{HF}+{\mathrm{NaAlF}}_4$

2. ${\mathrm{Al}}_2{\mathrm{O}}_3+{\mathrm{CaF}}_2+{\mathrm{NaAlF}}_4$

3. ${\mathrm{Al}}_2{\mathrm{O}}_3+{\mathrm{Na}}_3{\mathrm{AlF}}_6+{\mathrm{CaF}}_2$

4. ${\mathrm{Al}}_2{\mathrm{O}}_3+\mathrm{KF}+{\mathrm{Na}}_3{\mathrm{AlF}}_6$

Which of the following has a negative slope?

1. C $\to$CO

2. Fe $\to$Fe₂O₃

3. Mg $\to$MgO

4. All of the above

The correct statement among the following is: