commercial bleach lab

I. Title: Analysis of a Commercial Bleach
II. Purpose:
III. Materials:
Commercial bleach, 5% NaClO. (5 mL).
Hydrochloric acid (HCl), 3M. (6 mL).
Potassium Iodide (KI). (6 g).
Sodium thiosulfate solution (Na2S2O3), 0.100 M. (70 mL).
Starch solution 2%. (3 mL). Safety goggles
Apron
Digital scale
Buret
Buret clamp
Erlenmeyer flask
Pipet bulb
Ring stand
Ttransfer pipet, 5 mL and 25 mL
Volumetric flask, 100 mL
Stopper
Wash bottle
Distilled water
Weigh boat
Beakers,
IV. Procedures:
1) Use the 5 mL transfer pipet and the pipet bulb to measure 5.00 mL of the commercial bleach and drop into a 100 mL volumetric flask.
2) Dilute to the 100 mL mark with distilled water. Put the stopper on and mix well.
3) Weigh out about 2 g of KI on the digital scale.
4) Use the 25 mL transfer pipet and bulb to pipet 25 mL of the dilute bleach into an Erlenmeyer flask.
5) Add the solid KI into the Erlenmeyer flask with about 25 mL of distilled water. Swirl to dissolve the KI
6) While working in the fume hood, add about 2 mL of the 3 M HCl while stirring the solution.
7) Fill the buret with the 0.10 M sodium thiosulfate. Record the initial buret reading and the solution molarity.
8) Titrate the solution with the 0.10 M sodium thiosulfate solution until the iodine color fades to a light color.
9) Then add one dropperful of starch solution. The blue color of the starch-iodine complex should appear.
10) Continue the titration until one drop of the 0.10 M sodium thiosulfate solution causes the blue color to disappear. Record the final buret reading.
11) Repeat the titration process, starting with step 3 two more tmes.

V. Data/Calculations

Data:
Molartiy of Na2S2O3

Trial 1
Trial 2
Trial3
Initial buret reading
0.00 mL
6.18 mL
25.42 mL
Final buret reading
18.21 mL
25.42 mL
44.28 mL
Volume Na2S2O3 added
18.21 mL
19.24 mL
18.86 mL

Calculations (post-lab calculations and analysis.)
1) Determine the number of moles of sodium