The reaction of divalent manganese with O 2 in aqueous solution is given as foll

Question

The reaction of divalent manganese with O2 in aqueous solution is given as follows: Mn2++1/2O2(aq) + H2O = MnO2(s) + 2H+.

Delfino and Lee found that a lake water sample devoid of oxygen, pH=8.5, originally contained 0.6mg/liter of Mn2+. The sample was aerated (atmosphereic conditions) and after 10 days of saturations with atmosphereic O2 the Mn2+ concentration was 0.4mg/liter.

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 at equlibrium?

Explanation / Answer

a) assuming the pH remains constant during aeration, the preipitate will not continue after 10th day once the aeration stops. This is due to the condtion of equilibrium reached by the reaction.

b) Mn2+ concentration at equilibrium,

Given Mn2+ after 10 days is 0.4 mg/L

convert it to mmoles/L

mmoles/L = mg/atomic mass of Mn = 0.4/55 = 0.007 mmol/L 0.007 mM

thus, concentration of Mn2+ at equlibrium would be 0.007 mM

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.