This document discusses the extraction of elements and the Ellingham diagram. It covers the following key points: 1) Elements exist in nature in combined, native, or free states and can be extracted via mechanical separation, thermal decomposition, displacement, high temperature chemical reduction, or electrolytic reduction depending on factors like reactivity and stability. 2) The Ellingham diagram plots the change in free energy (ΔG) with temperature for oxidation reactions of metals. It shows which metals can reduce the oxides of other metals based on their relative positions on the diagram. 3) The diagram is used to determine the temperature at which an oxide becomes unstable and decomposes based on where its line crosses the ΔG = 0

1. Shri Shivaji Education Society Amravati’s
J.D.Patil Sangludkar Mahavidyalaya,
Daryapur.
Extraction of Elements
Rahul G.Sawarkar
M.Sc. GATE. SET
Asst.Professor

2. Occurrence of Elements
Combined
State
Native state
(or free State)

3. Methods of Extraction of Process
 Mechanical separation of elements that exist in
the native form.
 Thermal decomposition methods.
 Displacement of one metal by another.
 High temperature chemical Reduction method.
 Electrolytic reduction.

5. Factors influencing the Choice of Extraction Process
Choice
of E.P.
Reactivity
Selection
Stability
Electrolytic
Reduction
Occurrence

6. The graphical
representation
of Gibb’s energy
was first used by
H.J.T. Ellingham
The Ellingham diagram for oxides showing change
in free energy ∆G with temperature

7. For a spontaneous reaction,
free energy change ∆G must be
negative.
We have, ∆ G = ΔH – T ΔS
Where,
ΔH is enthalpy change during
the reaction,
T is the absolute temperature,
and
Δ S is the change in entropy
during the reaction.

8. From the Ellingham diagram for oxides-
i) The graphs for metal to metal oxide,all
slope upwards, because the free energy
change increases with an increase of
temperature.
ii) The free energy changes for all, follow a
straight line, unless the materials melt or
vaporize.
iii) At temperature where a line crosses Δ G
= 0, the free energy of formation of the
oxide becomes positive, and the oxides
becomes unstable, and should decompose
into the metal and oxygen. Below this
temperature the free energy of formation of
the oxides is negative, so the oxide is stable.
When change of state occurs at a particular temperature, entropy increases and change
in slopes of line occurs.
Example: Hg-HgO line changes slope at 3560C, when Hg boils.
Similarly, Mg-MgO changes at 11200 C.

9. iv) Any metal will reduce the oxides of other
metals which lie above it in the Ellingham
diagram, because the free energy will
become more negative by an amount equal
to the difference between the two graphs at
that particular temperature.
Example:
Al reduces FeO, CrO and NiO, in the well known Thermite reaction,
but it cannot reduce MgO below 15000C (because above 15000C
graph of Mg-MgO lies above aluminum).