The choice of reducing agent for metal o...

The choice of reducing agent for metal oxide is decided by thermodynamic principles of metallurgy. `Delta G` must be negative. Ellingham diagram is a plot of `Delta_(f)G^(0)` vs T for the formation of oxides of various elements. All the plots slope upwards when temperature increases. Each plot is a straight line except when some change in phase takes place. A metal will reduce the oxide of other metals which lie above it in this diagram.
At a temperature below 1623 K. Al cannot reduce

FeO

CrO

MgO

NiO

Verified by Experts

The correct Answer is:

AI can.t reduce MgO as Mg is more electropositive.

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The choice of reducing agent for metal oxide is decided by thermodynamic principles of metallurgy. Delta G must be negative. Ellingham diagram is a plot of Delta_(f)G^(0) vs T for the formation of oxides of various elements. All the plots slope upwards when temperature increases. Each plot is a straight line except when some change in phase takes place. A metal will reduce the oxide of other metals which lie above it in this diagram. Delta G^(0) vs T plot in the Ellingham's diagram slopes downward for the reaction.

`Mg + (1)/(2)O_(2) rarr MgO`

`2Ag + (1)/(2) O_(2) rarr Ag_(2)O`

`C + (1)/(2) O_(2) rarr CO`

`CO + (1)/(2) O_(2) rarr CO_(2)`

Ellingham diagram

Free energy curve

Entropy curve

Isobar

is mostly `+ve`

is mostly `-ve`

depends on the type of metal

depends on the formula of metal oxide