An analytical chemist performs an experiment to determine the percentage by mass of sodium chlorate(I), NaClO\text{NaClO}NaClO, in a commercial disinfectant formulation.
Method:
The chemist requires a mean titre of 24.60 cm324.60\text{ cm}^324.60 cm3 of the sodium thiosulfate solution.
The density of the original disinfectant formulation is 1.12 g cm−31.12\text{ g cm}^{-3}1.12 g cm−3.
The relevant chemical equations for the reactions are: ClO−(aq)+2H+(aq)+2I−(aq)→Cl−(aq)+H2O(l)+I2(aq)\text{ClO}^-\text{(aq)} + 2\text{H}^+\text{(aq)} + 2\text{I}^-\text{(aq)} \rightarrow \text{Cl}^-\text{(aq)} + \text{H}_2\text{O(l)} + \text{I}_2\text{(aq)}ClO−(aq)+2H+(aq)+2I−(aq)→Cl−(aq)+H2O(l)+I2(aq) 2S2O32−(aq)+I2(aq)→2I−(aq)+S4O62−(aq)2\text{S}_2\text{O}_3^{2-}\text{(aq)} + \text{I}_2\text{(aq)} \rightarrow 2\text{I}^-\text{(aq)} + \text{S}_4\text{O}_6^{2-}\text{(aq)}2S2O32−(aq)+I2(aq)→2I−(aq)+S4O62−(aq)
Calculate the percentage by mass of NaClO\text{NaClO}NaClO in the original disinfectant formulation. Give your answer to 3 significant figures.
The total uncertainty associated with the burette readings and the end-point determination is ±0.12 cm3\pm 0.12\text{ cm}^3±0.12 cm3. Calculate the total percentage uncertainty in using the burette for this titration. Give your answer to 3 significant figures.