Chemistry Report

1
Chemistry Report

• Analysis of the effectiveness of three commercial
  brands of bleaching solution

2
Uses of bleaches

• Sterilization
• Clean sinks work surfaces
• Clean bleach laundry

3
Introduction

• Sodium hypochlorite (Sodium Chlorate(I))
  (NaClO) forms the basis of the most commercial
  bleaches. The amount of this active ingredient
  available can be estimated by the following
  method.
• In this technique, the Sodium Chlorate
  (I) is allowed to react with an excess of
  Potassium Iodide (KI) solution in the presence of
  acid, liberating Iodine, which is then TITRATED
  against Standard Sodium Thiosulphate (Na2S2O3)
  solution.

4
Chemicals

• 0.05016M of Sodium thiosulphate
• 0.1M of Potassium Iodide
• 1M of Sulphuric acid
• Starch solution (For indicator)

5
Reaction Involved

• ClO- (aq) 2I- (aq) 2H (aq)
• I2 (aq) H2O (l) Cl- (aq)
• I2(aq) 2S2O3 2- (aq)
• 2I-
  (aq) S4O6 2- (aq)

6
Apparatus

• Pipette
• Conical flask
• Burette
• Volumetric flask
• Breaker
• Measuring cylinder

7
Samples used

• Nelli
• Total volume 600ml
• Price 5
• Park nShop
• Total volume 2L
• Price 10.9
• Wellcome
• Total volume 2L
• Price 10.9

8
Procedure

• Pipette exactly 10 cm3 of the bleach into a clean
  volumetric flask (250 cm3 capacity)
• Make up to the mark using distilled water.
  Shaking well
• Pipette 25cm3 of this solution into a conical
  flask, add 30 cm3 of 0.1M Potassium Iodide
  solution and 10 cm3 of 1M Sulphuric acid.
• Titrate this against the Standard Sodium
  Thiosulphate solution provided and record the
  results in a table.

9
Result

• NELLI
• The mean of volume of Na2S2O3 used 30.63cm3
• The amount of active ingredient 47.312g dm-3
• The gram per dollar 5.677g per dollar
• PARK NSHOP
• The mean of volume of Na2S2O3 used 14.17cm3
• The amount of active ingredient 18.302g dm-3
• The gram per dollar 3.358g per gram
• WELLCOME
• The mean of volume of Na2S2O3 used 31.50cm3
• The amount of active ingredient 40.69g dm-3
• The gram per dollar 3.733g per dollar

10
Error

• Starch solution is not fresh because it is
  oxidized.
• Potassium iodide is not enough to react all ClO-
  ions
• Parallax occurs when recording the reading of
  burette.

11
Precaution

• We should wear safety goggles when sulphuric acid
  is used.
• I2 is added as soon as possible because it
  vapours easily.
• Starch solution cannot be added too early
  otherwise, the black precipitate is formed.
• White tile is placed under the conical flask
  during titration for observation the colour
  change easily.

12
Conclusion

• After the titration and calculation, the bleach
  which has the best effectiveness is the brand of
  Nelli, compared with the other brands of Park
  NShop and Wellcome.