A student is analyzing the unbalanced reaction that occurs when iodate ions react…
CHEMISTRY · Multi-part · A Level · Chemistry · Oxidation, reduction and redox reactions · Oxidation, reduction and redox reactions
Problem
A student is analyzing the unbalanced reaction that occurs when iodate ions react with arsenite ions in strongly basic aqueous solution to form arsenate ions and iodide ions.
Unbalanced skeletal equation (basic solution):
IO3−+AsO33−→AsO43−+I−
In planning to balance this reaction, the student decides to separate the process into an oxidation half-reaction and a reduction half-reaction before combining them into a single overall equation.
(1) Part 1: (a) Identify which reactant is oxidized and which reactant is reduced. Justify your answers by citing oxidation‐state changes for the relevant atoms.
(2) Part 2: (b) Explain why the number of electrons lost in the oxidation half-reaction must exactly equal the number of electrons gained in the reduction half-reaction when the two half-reactions are combined.
(3) Part 3: (c) While balancing, the student obtains intermediate steps that contain H+ ions. Describe, in words, the procedure that must be carried out to eliminate every H+ ion from the intermediate steps so that the final equation is consistent with strongly basic reaction conditions.
(4) Part 4: (d) In the final balanced equation, hydroxide ions and water molecules frequently appear on opposite sides. Explain how the presence of both species in the balanced equation can still satisfy overall charge and atom balance in a basic medium.