a write a balanced redox ctt thiosulfate ion equation for the reaction between iodine and 2s 03 a j1 s2o3 thiosulfate ion szo3 44668 will be oxidised to the tetrathionate ion b the concentr 69032

(a) Write a balanced redox equation for the reaction between iodine and thiosulfate ion, S2O3^2-. Thiosulfate ion, S2O3^2-, will be oxidized to the tetrathionate ion. (b) The concentration of commercial bleach can be estimated by the amount of free chlorine in the solution. 10.0 cm^3 of a sample of bleach was made up to a 250.0 cm^3 standard flask. 25.0 cm^3 of this solution were added to an excess of aqueous potassium iodide and reacted with 22.0 cm^3 of 0.105 mol dm^-3 thiosulfate solution. Calculate the concentration of chlorine in the diluted bleach solution.

The amount of sodium hypochlorite in a bleach solution can be determined by using a given volume of bleach to oxidize excess iodide ion to iodine; $\mathrm{ClO}^{-}$ is reduced to $\mathrm{Cl}^{-}$. The amount of iodine produced by the redox reaction is determined by titration with sodium thiosulfate, $\mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3} ; \mathrm{I}_{2}$ is reduced to $\mathrm{I}^{-}$. The sodium thiosulfate is oxidized to sodium tetrathionate, $\mathrm{Na}_{2} \mathrm{~S}_{4} \mathrm{O}_{6} .$ In this analysis, potassium iodide was added in excess to $5.00 \mathrm{~mL}$ of bleach $\left(d=1.00 \mathrm{~g} / \mathrm{cm}^{3}\right) .$ If $25.00 \mathrm{~mL}$ of $0.0700 \mathrm{M} \mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}$ was required to reduce all the iodine produced by the bleach back to iodide, what is the mass percent of $\mathrm{NaClO}$ in the bleach?

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