8 Marks: 1 Consider the following half-reaction. 4H + (aq) + O 2 (g) + 4e - ? 2H
ID: 835242 • Letter: 8
Question
8
Marks: 1
Consider the following half-reaction.
4H+(aq) + O2(g) + 4e- ? 2H2O(l) Eo = 1.23 V
What is E, if the pressure of oxygen gas is 1.0 atmosphere and the pH is 5.31?
USE 2 DECIMAL PLACES. (Hint, are solids and pure liquids included in Q? Using LeChatelier's principle is E going to be larger or smaller?)
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11
Marks: 1
Mg2C2O4(s) ? 2Mg2+(aq) +C2O42-(aq) Ksp = 8.6 x 10-5
What is Qsp if 100 mL of 0.063 M Mg(N03)2 is added to 50 mL of 0.021 M Na2C2O4?
Recall that if Qsp is greater than Ksp, a precipitate forms.
Explanation / Answer
8)E=E-(R/n)log(Q)
E=1.23-(0.0591/4)log(1/10^-5.31)
E=1.15V
11)Qsp = [Mg 2+ ]^2 [C2O4 2-]
=[ 100*.063 / 150 ]^2 [ 50*.021/ 150]
=1.235e-5
ACS II....Study for the finals good luck
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