Use the following reaction to answer the question. 2 A l ( s )+ 3/2 O 2( g ) A l
ID: 697755 • Letter: U
Question
Use the following reaction to answer the question.
2Al (s)+ 3/2 O2(g)Al2O3(s) Gr0
Think about another reaction, 2Au(s)+ 3/2 O2(g)Au2O3 (s), which has a much lower reaction Gibbs free energy (in absolute value) than Gr0.
What will be the equilibrium oxygen partial pressure in the gold oxidation reaction compared to the aluminum oxidation?
A. Equilibrium oxygen partial pressure in gold oxidation is higher than aluminum oxidation
B. Equilibrium oxygen partial pressure in gold oxidation is lower than aluminum oxidation
C. Equilibrium oxygen partial pressure in gold oxidation is the same as aluminum oxidation
D. Not sure
Explanation / Answer
2Al (s)+ 3/2 O2(g)Al2O3(s); G1r0
2Au(s)+ 3/2 O2(g)Au2O3 (s); G2r0
G1r0 < 0 for the reaction to be spontaneous
Given that – G2r0 < - G1r0
Or G1r0 < G2r0
Go = -R T ln (Keq)
This implies that equilibrium constants
Keq2 < Keq1 .. eqn(1)
Keq2 = [Au2O3] / [Au]2 [O2]3/2
Keq1 = [Al2O3] / [Al]2 [O2]3/2
By comparison and using eqn (1) we get,
[O2] for the reaction 2 is higher than [O2] for reaction 1
Option A)