The oxidation of HSO₃⁻ by O₂ in aqueous solution is a reaction of importance to the processes of acid rain formation and flue gas desulfurization. R.E. Connick et al. (Inorg. Chem. 34, 4543 (1995)) report that the reaction 2 HSO₃⁻(aq)+O₂(g)→2 SO₄²⁻ (aq)+2 H⁺(aq) follows the rate law v=k_r [HSO₄⁻]²[H⁺]². Given pH=5.6 and an oxygen molar concentration of 0.24mmol dm⁻³ (both presumed constant), an initial HSO₃⁻ molar concentration of 50µmol dm⁻³, and a rate constant of 3.6×10⁶ dm⁹ mol⁻³ s⁻¹, what is the initial rate of reaction? How long would it take for HSO₃⁻ to reach half its initial concentration?