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St. Paul’s Secondary School Registration No. :BCh24

St. Paul’s Secondary School Registration No. :BCh24. 開心漂白大發現 The Bleach File. Introduction. Types of Chlorine bleach: 1. KAO Bleach 2. Clorox Bleach 3. No Frills Bleach 4. LibY Bleach Types of colour-safe bleach 1. Vanish in-wash stain remover (colour-safe)

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St. Paul’s Secondary School Registration No. :BCh24

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  1. St. Paul’s Secondary School RegistrationNo. :BCh24 開心漂白大發現 The Bleach File

  2. Introduction • Types of Chlorine bleach: • 1. KAO Bleach • 2. Clorox Bleach • 3. No Frills Bleach • 4. LibY Bleach • Types of colour-safe bleach • 1. Vanish in-wash stain remover (colour-safe) • 2. KAO Liquid Wide Bleach.

  3. Content • Working principles • Chemical content • Cleansing power towards different types of stains • Possible damages to cloth • Effect of mixing chlorine bleach and colour-safe bleach

  4. Chemical Content and Working Principles of Chlorine Bleach and Colour-Safe Bleach: • Oxidizing power of thehypochlorous acid HOCl (aq)in chlorine bleaches • Oxidizing power ofhydrogen peroxide H2O2 (aq)in colour-safe bleaches. • HOCl (aq) + D  H+ (aq) + Cl- (aq) + DO • H2O2 (aq) + D  H2O (l) + DO • Coloured Colourless

  5. Investigation Experiment 1 Aim: To find out the active ingredient in chlorine bleaches and colour safe bleaches I)To test for ClO- in chlorine bleaches: Equation Involved: OCl-(aq) + Cl-(aq) + 2H+(aq) Cl2 (g) + H2O (l)

  6. Testing of the gas evolved after mixing chlorine bleach with hydrochloric acid

  7. II) To test for H2O2 in colour safe bleaches: Equation involved: 2H2O2(aq) O2 (g) + 2H2O(l) • Results: • A gas was evolved • The glowing splint relighted, which suggests that the gas is oxygen.

  8. Conclusion: • Active ingredient in chlorine bleaches • hypochlorite ions • Active ingredient in colour safe bleaches • hydrogen peroxide

  9. Experiment 2 Aim: To determine the concentration of sodium hypochlorite in different brands of household chlorine bleaches.

  10. S2O32-(aq) Diluted chlorine bleach, KI and H2SO4 To determine the concentration of sodium hypochlorite in different brands of household chlorine bleaches Equations involved: 1) OCl-(aq) + 2I-(aq) + 2H+(aq) I2 (g) + Cl- (aq) + H2O (l) 2) I2 (aq) + 2S2O32-(aq) S4O62-(aq) + 2I-(aq) with starch added as indicator Titrated against S2O32-(aq) Starch added Colour change at end point: from blue to colourless

  11. Greatest molarity of NaOCl Conclusion:

  12. Best buy Price per mole of NaOCl ($) Brands of chlorine bleach

  13. Experiment 3 Aim: To determine the concentration of hydrogen peroxide in different brands of colour-safe bleach

  14. MnO4-(aq) Diluted colour-safe bleach To determine the concentration of hydrogen peroxide in different brands of colour-safe bleach Equation involved: 6H+(aq) + 2MnO4-(aq) + 5H2O2(l) 5O2(g) + 2Mn2+(aq) + 8H2O (l) Colour change at the end point: from colourlessto pale pink

  15. Highest molarity of H2O2 Best Buy Price per mole of H2O2 ($) Brands of colour safe bleach

  16. Price of the bleaches per number of moles of active ingredients in chlorine bleaches and colour-safe bleaches more expensive Price per mole of active ingredient ($) Chlorine bleaches Colour-safe bleaches

  17. Experiment 4 • Aim: • To investigate the cleansing power and possible damages to cloth of different chlorine/colour-safe bleaches. • Introduction: • Different kinds of cloths with different stains were soaked into different samples • Changes in textures and original colour of the fabrics, and the degree of removal of stains would be considered.

  18. 1.Curry stain Purple cotton fabric Towel with curry stain with curry stain

  19. 2.Dark Soy Sauce Stain Purple cotton fabric Towel with dark with dark soy sauce stain soy sauce stain

  20. 3.Black Ink Stain Purple cotton fabric with black ink stain Towel with black ink stain

  21. 4.Ketchup Stain Purple cotton fabric with ketchup stain Towel with ketchup stain

  22. 5.Marker (Black) and Highlight Pen (Green) Stains Purple cotton fabric with marker and highlight pen stains Towel with marker and highlight pen stains

  23. Analysis of Results: 1)  Curry Stain ‘Kao Bleach’ bleached the curry stains most effectively. 2)  Black Ink Stain Colour-safe bleach bleached the black ink stain much better than chlorine bleaches.

  24. Similar performance on 3)  Dark Soy Sauce Stain 4)  Ketchup Stain 5)  Marker and Highlight Pen Stains

  25. 6.White cotton fabrics     One piece of white cotton fabric was dipped into each of the four different kinds of undiluted chlorine bleach for three days. Result: The pieces of white cotton fabric turned palerand thinner than the original sample. LibY Bleach No Frills Bleach KAO Bleach Clorox Bleach Original sample

  26. 7.Coloured checked fabrics     One piece of coloured checked fabric was dipped into each of the two different kinds of colour-safe bleach for three days. Result: No obvious change in colour and texture.

  27. VANISH Conclusion: The BEST stain remover:

  28. Experiment 5 • Aim: • To investigate theconsequences of mixing household chlorine bleach and colour-safe bleach • Questions in mind: ?? • What will happen if household chlorine bleach is mixed with colour-safe bleach? • Will the effectiveness of the bleaching action be increased upon mixing?

  29. Chlorine bleach Colour-safe bleach

  30. High density white foam was evolved • Heat was produced

  31. The beaker of foam finally overflowed.

  32. ` To collect the gas produced: - by displacement of water

  33. Test result: The glowing splintrelighted which shows that the gas was oxygen.

  34. Conclusion: • Redox reactionhappened between hydrogen peroxide andhypochlorite ion. • Equations involved: • OCl-(aq) + H2O2(l) Cl-(aq) + O2(g) + H2O(l) • (O.A.) (R.A.) • An exothermic reaction • The oxygen formed causes the formation of the high density white foam.

  35. Recommendation: Never mix them together Adding Chlorine Bleach A lot of foam and heat are produced Colour- safe bleach

  36. Do you know how to choose between chlorine bleach and colour safe bleach now?

  37. St. Paul’s Secondary School Registration No. :BCh24 Group members: Ivy Yeung Vivien Chu Helen Kwai Maggie Chow Amelia Ho Teacher Advisors: Mrs. A. Lam Miss I. Lau

  38. The End

  39. Summary • “Kao Bleach” has the highest concentration of hypochlorite ions among the four chlorine bleaches • “Vanish Stain Remover” has the highest concentration of hydrogen peroxide among the two colour-safe bleaches. • The best buy of chlorine bleach is “LibY Bleach” and that of colour-safe bleach is “Vanish”. • “Vanish” was found to be the best stain remover among all brands of bleaches and it does not affect the original colour of the fabric. • Chlorine bleach cannot be mixed with colour-safe bleach when use, or else they will lose their bleaching power and produce excess foam.

  40. Discussion • 1. Pros and cons of using the 2 different bleaches • Chlorine Bleach • Pros: • cheaper and easily available. • can be used as disinfectant. • turns yellowish white fabrics back to its original • white colour. • removes mildew on shower curtains, bath tubs, etc.

  41. Chlorine Bleach • Cons: • Chlorine is a toxic chemical. • irritates eyes and skin. • cannot be used on coloured fabrics • cannot be used to bleach delicate fabrics such as silk. • causes water pollution.

  42. -  Environmental impact concerning the use of chlorine bleach:  Excessive use of bleaches may cause damage to the water pipes due to its corrosive nature.  Causes eutrophication in river and sea.  Toxic substances may produce and will stay in water and accumulate in the food chain.

  43. H2O2 Bleach • Pros: • H2O2 is a stronger oxidizing agent than NaOCl, the bleaching actions of H2O2 is faster, yet it does not cause any damage to fabrics. • It is environmental friendly. • The colour of fabrics being bleached will not lose its original colour.

  44. H2O2 Bleach • Cons: • Residual of H2O2 on clothes causes skin problems. • It is more expensive than chlorine bleach. • H2O2 is unstable and easily decomposes at high temperature, thus it cannot be stored for a long period of time.

  45. Further Investigation: • Possible factors affecting the bleaching power of the bleaches: • Temperature • pH values

  46. How does bleach remove colour in organic compounds? Colour in organic materials is the result of light absorption by certain chemical configurations called chromophores in molecules. C=C and C=O bonds are examples of chromophores. A chromophore, e.g. C=C and C=O, is a part of a molecule that is able to absorb UVlightor visible light and producing colour in organic compounds. Oxidizing bleaches break up these double bonds : Reducing bleaches convert double bonds to single bonds:

  47. Prices of different bleaches: Kao Bleach : $14.9 per 600ml Clorox Bleach : $7.9 per 710ml No Frills : $9.9 per 2000ml LibY Bleach : $6.2 per 1500ml Prices of different colour-safe bleaches: Vanish Stain Remover : $19.9 per 1kg Kao Liquid Wide Bleach : $17.9 per 1000ml

  48. E(V)Half equation +0.68 O2 + 2H+ + 2e-  H2O2 + 0.89 ClO- +H2O + 2e- Cl- + 2OH- +1.77 H2O2 + 2H+ + 2e-  2H2O2

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