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)
2.
KAO Liquid Wide Bleach.
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
Chemical Content and Working Principles of
Chlorine Bleach and Colour-Safe Bleach:
•Oxidizing power of the hypochlorous acid
HOCl (aq) in chlorine bleaches
•Oxidizing power of hydrogen peroxide
H2O2 (aq) in colour-safe bleaches.
HOCl (aq) + D
 H+ (aq) + Cl- (aq) + DO
H2O2 (aq) + D
 H2O (l)
Coloured
+
DO
Colourless
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)
Testing of the gas evolved after mixing
chlorine bleach with hydrochloric acid
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.
Conclusion:
Active ingredient in chlorine bleaches
hypochlorite ions
Active ingredient in colour safe bleaches
hydrogen peroxide
Experiment 2
Aim:
To determine the concentration of sodium
hypochlorite in different brands of
household chlorine bleaches.
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) S2O32- (aq)
2) I2 (aq) + 2S2O32- (aq)  S4O62- (aq) + 2I- (aq)
with starch added as indicator
Titrated against
S2O32- (aq)
Diluted chlorine
bleach, KI and
H2SO4
Starch
added
Colour change at end point: from blue to colourless
Conclusion:
Brands of
chlorine
bleach
Kao Bleach
Clorox Bleach
No Frills
Bleach
LibY Bleach
Molarity of
NaOCl
2.2M
2.12M
1.99M
1.88M
Greatest
molarity
of
NaOCl
Brands of
bleach
Kao Bleach
Price of bleach
per mole of
NaOCl
$11.3
Clorox Bleach
$6.21
No Frills Bleach
$2.49
LibY Bleach
$2.20
Best buy
12
Price
per mole
of
NaOCl
($)
10
8
6
4
2
0
Ka o
Clorox
No Frills
Brands of chlorine bleach
LibY
Experiment 3
Aim:
To determine the concentration of
hydrogen peroxide in different brands of
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)
MnO4- (aq)
Colour change at the
end point: from
colourless to pale pink
Diluted
colour-safe
bleach
Molarity of Price of bleach
per mole of
H 2O 2
H2O2
Vanish Stain 1.90M
$10.6
Highest
Best
Remover
molarity of
Buy
Kao
Liquid
1.38M
$13.0
H2 O2
Wide Bleach
Brands of
bleach
14
12
Price per
mole of
H2O2 ($)
10
8
6
4
2
0
Vanish
Kao
Brands of colour safe bleach
Price of the bleaches per number of moles of active
ingredients in chlorine bleaches and colour-safe bleaches
Vanish
Kao Liquid Wide
Chlorine bleaches
LibY
No Frills
Clorox
Kao
14
12
10
8
Price per
6
mole of
4
active
2
ingredient 0
($)
more expensive
Colour-safe bleaches
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.
1.Curry stain
Purple cotton fabric
with curry stain
Towel with curry stain
2.Dark Soy Sauce Stain
Purple cotton fabric
with dark soy sauce stain
Towel with dark
soy sauce stain
3.Black Ink Stain
Purple cotton
fabric with black
ink stain
Towel with
black ink stain
4.Ketchup Stain
Purple cotton fabric
with ketchup stain
Towel with
ketchup stain
5.Marker (Black) and Highlight Pen (Green)
Stains
Purple cotton fabric
with marker and
highlight pen stains
Towel with
marker and
highlight pen
stains
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.
Similar
performance on
3) Dark Soy Sauce Stain
4) Ketchup Stain
5) Marker and Highlight Pen Stains
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
paler and
thinner than the
original sample.
KAO Bleach
Original sample
LibY Bleach
Clorox Bleach
No Frills Bleach
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.
Conclusion:
The BEST stain remover:
VANISH
Experiment 5
Aim:
To investigate the consequences 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?
Colour-safe bleach Chlorine bleach
•High density white foam was evolved
•Heat was produced
The beaker of foam finally overflowed.
To collect the gas produced:
` water
- by displacement of
Test result:
The glowing splint relighted which shows that
the gas was oxygen.
Conclusion:
•Redox reaction happened between
hydrogen peroxide and hypochlorite 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.
A lot of
foam and
heat are
produced
Adding
Chlorine
Bleach
Coloursafe
bleach
Do you know how to choose
between chlorine bleach and
colour safe bleach now?
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
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.
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.
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.
- 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.
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.
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.
Further Investigation:
Possible factors affecting the bleaching power
of the bleaches:
•Temperature
•pH values
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 UV light or visible light and
producing colour in organic compounds.
Oxidizing bleaches break up these double bonds :
H
O
[O]
H C C
C C H
O O
O O
H C C OH
+
HO C C H
O
H
COLOURLESS
COLOURED
Reducing bleaches convert double bonds to single bonds:
H
O
[H]
H C C
H
C C H
OH
H CHCH2CH2CH2
O
COLOURED
OH
COLOURLESS
Prices of different bleaches:
Kao Bleach
: $14.9 per 600ml
Clorox Bleach : $7.9 per 710ml
No Frills
: $9.9
LibY Bleach
per 2000ml
: $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
E(V)
+0.68
Half equation
O2 + 2H+ + 2e-  H2O2
+ 0.89
ClO- +H2O + 2e-  Cl- + 2OH-
+1.77
H2O2 + 2H+ + 2e-  2H2O2