The amount of oxygen, O₂, dissolved in a water sample at 25°C can be determined by titration. The first step is to add solutions of MnSO₄ and NaOH to the water to convert the dissolved oxygen to MnO₂. A solution of H₂SO₄ and KI is then added to convert the MnO₂ to Mn²⁺, and the iodide ion is converted to I₂. The I₂ is then titrated with standardized Na₂S₂O₃.
(a) Balance the equation for the reaction of Mn²⁺ ions with O₂ in basic solution.
(b) Balance the equation for the reaction of MnO₂ with I⁻ in acid solution.
(c) Balance the equation for the reaction of S₂O₃²⁻ with I₂.
(d) Calculate the amount of O₂ in 25.0 mL of water if the titration requires 2.45 mL of 0.0112 M Na₂S₂O₃ solution.