Which of the following reactions is an example of auto reduction?

1.  ${\mathrm{Fe}}_3{\mathrm{O}}_4 + 4\mathrm{CO} \stackrel{}{\to } 3\mathrm{Fe} + 4{\mathrm{CO}}_2$

2.  ${\mathrm{Cu}}_2\mathrm{O} + \mathrm{C} \stackrel{}{\to } 2\mathrm{Cu} + \mathrm{CO}$

3.  ${\mathrm{Cu}}^{2+} \left(\mathrm{aq}\right) + \mathrm{Fe} \left(\mathrm{s}\right) \stackrel{}{\to } \mathrm{Cu} \left(\mathrm{s}\right) + {\mathrm{Fe}}^{2+}\left(\mathrm{aq}\right)$

4.  ${\mathrm{Cu}}_2\mathrm{O} + \frac{1}{2} {\mathrm{Cu}}_2\mathrm{S} \stackrel{}{\to } 3\mathrm{Cu} + \frac{1}{2} {\mathrm{SO}}_2$

A number of elements are available in earth’s crust but most abundant elements are ____________.

1.  Al and Fe

2.  Al and Cu

3.  Fe and Cu

4.  Cu and Ag

Zone refining is based on the principle that ___________.
 

In the metallurgy of aluminium ________________.

Electrolytic refining is used to purify which of the following metals?

1.  Cu and Zn

2.  Ge and Si

3.  Zr and Ti

4.  Zn and Hg

Answer the question on the basis of Figure

Choose the correct option of temperature at which carbon reduces FeO to iron and produces CO.

1.  Below temperature at point A.

2.  Approximately at the temperature corresponding to point A.

3.  Above temperature at point A but below the temperature at point D.

4.  Above temperature at point A.

Match the items of Column I with items of Column II and assign the correct code:

         Column I            Column II

(A) Pendulum         (1) Chrome steel

(B) Malachite          (2) Nickel steel

(C) Calamine          (3) ${\mathrm{Na}}_3{\mathrm{AlF}}_6$

(D) Cryolite            (4) ${\mathrm{CuCO}}_3.\mathrm{Cu} {\left(\mathrm{OH}\right)}_2$

                             (5) ${\mathrm{ZnCO}}_3$

1.  A (1)  B (2)  C (3)  D (4)

2.  A (2)  B (4)  C (5)  D (3)

3.  A (2)  B (3)  C (4)  D (5)

4.  A (4)  B (5)  C (3)  D (2)

Match the items of Column I with the items of Column II and assign the correct
code :

1. A =(1); B=(2); C=(4); D=(5)

2. A=(4); B=(3); C=(1); D=(2)

3. A=(3); B=(4); C=(2); D=(1)

4. A=(5); B=(4); C=(3); D=(2)

Match the items of Column I with the items of Column II and assign the correct code :

     Column I             Column II

(A) Sapphire           (1) ${\mathrm{Al}}_2{\mathrm{O}}_3$
(B) Sphalerite         (2) NaCN
(C) Depressant       (3) Co
(D) Corundum        (4) ZnS
                             (5) ${\mathrm{Fe}}_2{\mathrm{O}}_3$

1.  A (3)  B (4)  C (2)  D (1)

2.  A (5)  B (4)  C (3)  D (2)

3.  A (2)  B (3)  C (4)  D (5)

4.  A (1)  B (2)  C (3)  D (4)

Match the items of Column I with items of Column II and assign the correct
code :