CHEM 2115 Bleach Analysis Report Experiment #10 Chem I Lab

Name Section# Station# Date

Attach sample calculations of each type necessary to obtain the results (indicated in bold) for all parts of the experiment as described in the following tables. These should include the equations used, substituted values, and results.

I. Oxidation/Reduction Reactions

Below are the two reactions you observed in this experiment. For each, identify the substance oxidized and the substance reduced. Be sure to justify your answer.

(a)  ClO- aq+ 2 H+ aq+ 2 I- aq→I2 aq+ Cl- aq+ H2O l

(b)  2 S2O3-2 aq+ I2 aq→S4O6-2 aq+ 2 I- (aq)

II. Analysis of Commercial Clorox Bleach

Trial 1 / Trial 2 / Trial 3
Mass of bleach sample (g)
Buret reading, final (mL)
Buret reading, initial (mL)
Volume of NaS2O3 added (mL)
Moles of NaS2O3 added
Moles NaClO in bleach
Mass NaClO in bleach
Mass % NaClO in bleach
Average Mass % NaClO in Clorox bleach

III. Analysis of Generic “Dollar Store” Bleach

Trial 1 / Trial 2 / Trial 3
Mass of bleach sample (g)
Buret Reading, final (mL)
Buret Reading, initial (mL)
Volume of NaS2O3 added (mL)
Moles of NaS2O3 added
Moles NaClO in bleach
Mass NaClO in bleach
Mass % NaClO in bleach
Average Mass % NaClO in generic bleach

IV. Class Data Analysis

Class data for this experiment can be downloaded from Blackboard in which each student will have entered results of the six titrations (three for each bleach type). Use Excel to determine the class average weight percent NaClO and standard deviation for each bleach type.

Class average results: Report the results of your calculations of the class average values for the mass % NaClO for each bleach type and the standard deviation. Report your results as: AVERAGE ± STD DEV. In addition, note any data points that were discarded in the averaging of the data and justification as to why they were excluded.

Clorox / Generic
Mass % NaClO
  1. Compare the class average mass percent of NaClO determined for the two bleach types.
  1. What conclusions can you draw regarding the age and/or storage conditions of the generic based on the class results?
  1. Based on the class results, will a 1:10 dilution of each bleach type be useful for disinfection?

V. Some Questions About the Experimental Procedure

Explain how the following situations would impact the calculated weight percent NaClO in bleach. Would the calculated % NaClO increase, decrease, or remain unchanged? In each case be sure to justify your answer.

  1. 5 mL of 3 M potassium iodide (KI) is added instead of the 3 mL specified in the procedure
  1. The endpoint of the titration is exceeded by 0.5 mL
  1. The concentration of standard sodium thiosulfate is mistakenly recorded as 0.434 M