The reaction of chlorine gas with concentrated aqueous sodium hydroxide at elevated temperature produces both chloride and chlorate ions according to the balanced equation below.
3Cl2(g)+6OH−(aq)→5Cl−(aq)+ClO3−(aq)+3H2O(l)
This process is an example of a disproportionation reaction, in which the same element is simultaneously oxidized and reduced.
a. Assign oxidation numbers to chlorine in each of the three chlorine-containing species that appear in the equation above.
b. Identify the chlorine-containing species that is oxidized and the one that is reduced.
c. Explain, in terms of oxidation-number changes, why this reaction qualifies as a disproportionation reaction.