In pyrometallurgical processes, a reducing agent is required to reduce the metal
ID: 554562 • Letter: I
Question
In pyrometallurgical processes, a reducing agent is required to reduce the metal ore/concentrate in the form of oxides or sulfates to elemental metal. Ellingham diagrams are the thermodynamic basis for the selection of a reducing agent. Using the Ellingham diagram provided, please determine whether, thermodyn 2. ally: a Carbon can be used to reduce Cr203 to Cr. If yes, at what temperatures [6 MARKS] b.-Mn can be used to reduce Cr203 ttr)If yes, at what temperatures [4 MARKS c. Which one would be your preferred choice of reducing agent. Why [3 MARKS]Explanation / Answer
In ellingham diagram cabon can act as a reducing agent for all Metal oxides at very high temperature but chromium formed at high temperature reacts with carbon & forms its carbide so at high temperature reduction of chromic oxide, carbon cannot be used azz a reducing agent. more ever the greater the gap between any two lines in the ellingham diagram Greater the effectiveness of the reducing agent crossponding to lower lines as the gap between chromium and magnesium is very less Hence magnese will not be a good choice for reduction of chromic oxide in pyromettlurgical process.
Highly electropositive metals like Sodium Potassium Lithium aluminium etc to reduce the less electropositive metals like chromium copper magnese etc.
The Ellen gum ka for aluminium lies below the car of mass metals such as chromium manganese it is it is fact indicates the aluminium can be used as a reducing agent for oxides of all metals. The free energy of formation of chromium oxide and Aluminium oxide per mole of oxygen consumed are -540kJ & -827 kj respectively. The overall reaction will be given as follows
2/3 Cr2O3 + 4/3 Al = 2/3 Al2O3 +4/3 Cr , G = -287KJ
So Aluminium oxide is more stable than chromium oxide since the Gibbs free energy change is negative aluminium can reduce Cr2O3 in pyromettlurgical process. Pyrometallurgical vs Aluminium is used as a reducing agent to extract chromium and manganese reduction of their oxides.