The production of metals from their ones is usually very expensive due to the hi
ID: 996169 • Letter: T
Question
The production of metals from their ones is usually very expensive due to the high energy costs. The reaction for the production of Sn metal from SnO ore is: 2Sno (s) rightarrow 2Sn (s) + O_2(g) Delta G = ? Calculate Delta G for the reaction above using Delta G_f= - 286 kj/mole for SnO at 298K. Is Keq for this reaction as it is written at 298 K a very large or very small number? Is the reaction product favored at 298? For the conversion o f the SnO to Sn it is often reacted with CO in the reaction. 2 CO (g) + O_2(g) rightarrow 2 CO_2 (g) Delta G = - 498 kJ/mole at 298K. Show how coupling these two reactions will make a more favorable process for the production of Sn metal by calculating the Delta G for the combined process at 298 K. How would this reduce costs for production o f the Sn metal?Explanation / Answer
Given transformation,
2SnO (s) ----------> 2Sn (s) + O2 (g)
a) G = ?
G = Gf(Products) - Gf(Reactants)
G = [Gf O2 (g) + 2 Gf Sn] – [2 x Gf SnO (s)]
G = [(0) + 2 (0)] – [ 2 x (-286)]
G = + 572 kJ
G = 572000 J
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b) As G is very high +ve Keq will be very small number because
G = -RT ln(Keq)
As G become more and more +ve Keq takes small and smaller value.
Also as G is +ve reaction is not favored in given direction at given temperature.
Hence at 298 K product is not favored.
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c) Second coupled reaction is,
2CO (g) + O2 (g) -----------> 2CO2 (g)
Given G = -498 kJ/mol
Combined reaction;
2SnO (s) + 2CO (g) ----------> 2Sn (s) + 2CO2 (g)
For this coupled reaction Gc = ?,
Gc = G first reaction + G for second reaction
Gc = +572 kJ + (-498 kJ)
Gc = 74 kJ …………………………. (much less than 572 kJ)
To make G = -ve now we have to increases to less extent than what would be non-coupled reaction where G = +572 kJ.
This will save fuel require to attain the high temperature.
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