Zinc cannot be extracted from zinc oxide via CO reduction because:

(Given:  Ellingham diagram)

 

The better reducing agent for ZnO is: 

1. C

2. CO

3. CO₂

4. ${\mathrm{CO}}_3^{2-}$

Al can reduce MgO under the following conditions:

1. Above 500 °C, Al can reduce MgO

2. Below 500 °C, Al can reduce MgO

3. Below 1350 °C, Al can reduce MgO

4. Above 1350 °C, Al can reduce MgO

The thermodynamic property useful for selecting the reducing agent is:

1. Gibbs free energy change .

2. Internal energy change.

3. Specific heat capacity.

4. None of the above.