thiosulfate ions (S2O3^2) disproportionate in acidic solution to give solid sulfur (S) and hydrogen sulfite ion (HSO3^-) 2 S2O3^2- (aq) + 2 H3O^+ (aq) -----------> 2 HSO3^- (aq) + 2 H2O (l) + 2 S (s) A.) A disproportionation reaction is a type of oxidation-reduction reaction. which species is oxidized and which is reduced? B.) If 1.0 mL of 55% HSO3^- by mass is obtained in the reaction, what mass of S2O3^2- was present initially, assuming the reaction went to completion? the density of the HSO3^- solution is 1.45 g/cm^3