To find the percent composition of sodium hypochlorite in commercial bleach
1. Titration: A method of analysis that will allow you to determine the precise endpoint of a reaction and therefore the precise quantity of reactant in the titration flask. A buret is used to deliver the second reactant to the flask and an indicator or pH Meter is used to detect the endpoint of the reaction.
1. Use a 5-mL transfer pipet to measure 5.00mL of commercial bleach solution into a 100-mL volumetric flask.
2. Dilute to the mark with distilled water, mix well.
3. Pipet 25.0 mL of the dilute bleach into an Erlenmeyer flask.
4. Add 2g solid KI and 25mL of stilled water into the Erlenmeyer flask. Swirl it.
5. In a fume hood, add 2 mL of 3M HCl into the Erlenmeyer flask.
6. Fill the buret with 0.100 M sodium thiosulfate solution. Record the initial buret reading.
7. Titrate with the 0.10M sodium thiosulfate solution until the iodine color fades to light yellow.
8. Add one dropperful of starch solution. The color of solution should turn to blue.
9. Continue the titration until one drop of Na2S2O3 solution causes the blue color to disappear. Record the final buret reading.
1. Oxidation: to lose of electrons
Reduction: to gain of electrons
2. (1) 2H++ClO-+2I- Cl-+I2+H2O
Oxi: 2I- I2+2e-
(3) I3+2S2O32- 3I-+S4O6¬2-
Red: I3-+2e- 3I-
Oxi: 2S2O32- S¬4O62-+2e-
3. Commercial bleach contains effective oxidizing agent. If the original solution is diluted, the oxidation and reduction occurs too quickly to observe the reaction and change of color.
4. Four 25.0-mL aliquots can be measured from a 100-mL volumetric flask.
Because in the procedure, after 5.00mL of commercial bleach solution was put in 100-mL volumetric flask, distilled water was poured in this flask, to the 100-Ml mark.
7. It is required to be very cautious as...