CHM 135 General Chemistry I Lab
Redox Titration of Bleach Report Sheet
Name
Section
Data for Standardization of Na2S2O3
Mass of KIO3 used to make solution
TRIAL 1
TRIAL 2
TRIAL 3
VOLUME KIO3
VOLUME Na2S2O3 USED
Calculation of Concentration of Na2S2O3
EQUATION
TRIAL 1 EXAMPLE
Moles KIO3 added to
250-mL volumetric
flask (Step 1)
Molarity KIO3 solution
prepared in Step 1
Moles KIO3 used in
titration (Step 2b)
Moles Na2S2O3 used in
titration (Step 2c)
Molarity of Na2S2O3
Data for Bleach Titration
TRIAL 1
MASS BLEACH
VOLUME Na2S2O3 USED
TRIAL 2
TRIAL 3
Calculation of Mass Percent of NaOCl in Bleach
EQUATION
TRIAL 1 EXAMPLE
Moles Na2S2O3 used in
titration (Step 3c)
Moles OCl- present
(Stoichiometry)
Mass of NaOCl
Mass Percent of NaOCl
in bleach
Results
Average Molarity of Na2S2O3
Average Experimental Mass Percent
of NaOCl in bleach
Reported Mass Percent of
NaOCl in bleach
Percent Difference in Mass Percents
Consider the equations on p. 66 of your lab manual. For each of the two reactions that
make up the standardization portion of the experiment, identify the oxidizing agent,
reducing agent, and the number of electrons transferred in the reaction:
KIO3 reaction:
Oxidizing agent:
Reducing agent:
Electrons transferred:
Na2S2O3 reaction:
Oxidizing agent:
Reducing agent:
Electrons transferred:
Consider the equations on p. 66 of your lab manual. For the first of the two reactions that
make up the titration of bleach (NaOCl) portion of the experiment, identify the oxidizing
agent, reducing agent, and the number of electrons transferred in the reaction:
NaOCl reaction:
Oxidizing agent:
Reducing agent:
Electrons transferred:
Imagine that you calculated an average molarity of your Na2S2O3 solution that was
greater than the true moalrity of the solution. Explain how this error will propagate in
calculation of the mass percent of NaOCl in the bleach.
In the question above, the mistake in the Na2S2O3 concentration would introduce a
systematic error in your results. Can you think of another possible systematic error that
could occur in this experiment?
Review your lab manual and find two examples of other oxidation-reduction reactions
that you have completed this semester – they may not be written out in the lab manual, so
look carefully. Write the balanced equations of the redox reactions here, and indicate
which species is oxidized in each case.