Concentrations of Solutions:

Since the reaction occurs in the mixing beaker, the concentrations of the reactants will be different because of dilution. The diluted concentration can be calculated by the general formula

where M_i is the initial concentration of the solution, and V_i is the initial volume added. V_f is the final volume of the solution. During a dilution process, the number of moles of solute does not change.

Concentration before Mixing:

Persulfate (S₂O₈^2-): This solution was prepared for you and the concentration was 0.10 M.

Potassium Iodide (KI): You prepared this solution by dissolving a weighed sample of KI in a 250.00 mL volumetric flask. The concentration can be calculated by

where the Mol. Wt. of KI is 166.01 g/mol

Thiosulfate (S₂O₃^2-):

You initially prepared this solution the week before in Expt. 11. As was discussed on the Preparation of a Sodium Thiosulfate Solution web page, the concentration is calculated by

For the iodine clock experiment, this solution was diluted. You pipetted 10.00 mL of stock thiosulfate solution into a 100.00 mL volumetric flask. Using eqn 4, the new concentration can be calculated

where 10.00 mL is the initial volume and 100.00 mL is the final volume.

Concentrations after Mixing:

You will use eqn 1 to calculate the diluted concentration of S₂O₈^2-, I^- and S₂O₃^2- in the mixing beaker. The final volume will be the sum of all the solutions added, including the ionic filters (KCl, and K₂SO₄) . The final volume is always approximately 50 mL.

Set up a table to summarize your data. For Example: