In acidic solution

CHEMISTRY · Multi-part · A Level · Chemistry · Oxidation, reduction and redox reactions · Oxidation, reduction and redox reactions

Problem

In acidic solution, chlorate ion reacts with iodide ion to produce chloride ion and iodate ion according to the unbalanced skeletal equation

\text{ClO}_3^- + \text{I}^- \rightarrow \text{Cl}^- + \text{IO}_3^-

This process has been proposed for the quantitative conversion of iodide in analytical chemistry. (a) Determine the oxidation number of chlorine in

\text{ClO}_3^-

and in

\text{Cl}^-

. Determine the oxidation number of iodine in

\text{I}^-

and in

\text{IO}_3^-

. Indicate the magnitude of the oxidation-number change for each element. (b) Balance the ionic equation for this reaction in acidic medium, using the smallest possible whole-number coefficients. (c) Convert your acidic-solution equation from part (b) to the corresponding equation that would operate in basic medium, clearly showing any additional species required. (d) How many moles of electrons are transferred per mole of chlorate ion consumed? Justify your answer by referencing stoichiometric coefficients from part (b). (e) A laboratory protocol calls for complete reaction of

0.250\,\text{mol}

of iodide ion with chlorate ion under acidic conditions. Calculate the mass (in grams) of solid

\text{KClO}_3

(molar mass

122.55\,\text{g}\,\text{mol}^{-1}

) required to supply the needed amount of chlorate ion.

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