The titration of 25.0 mL of an iron(II) solution required 18.0 mL of a 0.200 M solution of dichromate to reach the equivalence point. What is the molarity of the iron(II) solution?
Express your answer to three significant figures and include the appropriate units.
Oxidation-reduction reactions can be used for quantitative analyses of both solutions and solid samples. These analyses are based on the stoichiometry of the balanced equation for the reaction. Standard solutions of known concentration are used to completely react with the unknown solution. The concentration of the standard solution and the volume used in the titration are accurately known and are used to calculate the concentration or amount of the analyte solution.
The amount of iron in ore can be quantitatively determined by titrating a solution of the unknown with a standard solution of dichromate, Cr2O72−. The net ionic equation is:
6 Fe2+(aq) + Cr2O72−(aq) + 14 H+(aq) → 6 Fe3+(aq) + 2 Cr3+(aq) + 7 H2O(aq)
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