The reaction of divalent manganese with oxygen in aqueous solution is given as follows: Mn2+ + 1/2O2(aq) + H2O = MnO2(s) + 2H+ The equilibrium constant (K) for this reaction is 23.7. It has been found that a lake water sample that contains no oxygen at 25 C, pH = 8.5, originally contained 0.6 mg/L of Mn2+. The sample was aerated (atmospheric conditions of the dissolved oxyen concentration is 9.2 mg/L) and after 10 days of contact with atmospheric oxygen, the Mn2+ concentration was 0.4 mg/L. The molecular weight of Mn is 55, O is 16 and H is 1. The change in free energy of formation at standard conditions (kcal/mole) are as follows: Mn2+ = -54.4, O2(aq) = +3.93, H2O = -56.69, MnO2(s) = -111.1, H+ = 0. (a) Assuming that the pH remains constant during aeration, will the precipitate continue to form after the measurement on the tenth day? (b) What should the Mn2+ concentration be (in moles/L) at equilibrium, assuming that pH and presence of dissolved oxygen are the same as in part "a". Assume ideal conditions
The reaction of divalent manganese with oxygen in aqueous solution is given as follows:
Mn2+ + 1/2O2(aq) + H2O = MnO2(s) + 2H+
The equilibrium constant (K) for this reaction is 23.7. It has been found that a lake water sample that contains no oxygen at 25 C, pH = 8.5, originally contained 0.6 mg/L of Mn2+. The sample was aerated (atmospheric conditions of the dissolved oxyen concentration is 9.2 mg/L) and after 10 days of contact with atmospheric oxygen, the Mn2+ concentration was 0.4 mg/L. The molecular weight of Mn is 55, O is 16 and H is 1. The change in free energy of formation at standard conditions (kcal/mole) are as follows: Mn2+ = -54.4, O2(aq) = +3.93, H2O = -56.69, MnO2(s) = -111.1, H+ = 0.
(a) Assuming that the pH remains constant during aeration, will the precipitate continue to form after the measurement on the tenth day?
(b) What should the Mn2+ concentration be (in moles/L) at equilibrium, assuming that pH and presence of dissolved oxygen are the same as in part "a". Assume ideal conditions
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