An visual aid project

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An visual aid project

• Luk wing sing
• S97035880

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Action of chlorine bleach and sulphur dioxide on
coloured substances
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Action of chlorine bleach and sulphur dioxide on
coloured substances
Revision
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Revision
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ChemistryRevision

• 1. Bleaching action of sulphur dioxide
• SO2(g) dye (coloured)

• SO42-(aq) dye-O (colourless)

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ChemistryRevision on

• 2. Reducing properties of sulphite (action on
  bromine water)
• SO32-(aq) Br2(aq) (brown) 2H2O(l)

• SO42-(aq) 2Br-(aq) (colourless) 4H(aq)

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ChemistryRevision on

• 3. Reducing properties of sulphite (action on
  acidified potassium dichromate)
• 3SO32-(aq) Cr2O72-(aq) (orange) 2H(aq)

• 3SO42-(aq) 2Cr3(aq) (green) 2H2O(l)

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Comparing bleaching actions
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Chemistry Comparing bleaching actions

• Chlorine water chlorine bleach

• Aqueous
• sulphur dioxide

• 1.Species responsible for the bleaching

• HOCl(aq)

• SO2(aq)

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Chemistry Comparing bleaching actions

• Chlorine water chlorine bleach

• Aqueous
• sulphur dioxide

• 2. Bleach by oxidation or reduction?

• By oxidation

• By reduction

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Chemistry Comparing bleaching actions

• Chlorine water chlorine bleach

• Aqueous
• sulphur dioxide

• 3. Bleaching effect permanent?

• Original colour will be restored later

• Last for a long time

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Chemistry Comparing bleaching actions

• Chlorine water chlorine bleach

• Aqueous
• sulphur dioxide

• 4. Rare of bleaching?

• Faster and more vigorous

• Slower and milder

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Chemistry Comparing bleaching actions

• Chlorine water chlorine bleach

• Aqueous
• sulphur dioxide

• 5. What does it bleaching?

• Wool, silk, paper, some food

• Cotton, linen, some food stains

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Different use of bleach
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Different use of bleach

• Chlorine
• 1. Bleach cotton, linen and plant fibers
• 2. Kill germ in drinking water and swimming pools

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Different use of bleach

• Sulphur dioxide
• 1. Bleach wool, skill, straw and paper

• 2. Whiten some foods stuffs (flour, cheese)

• 3. Food preservative for dried fruits and jam

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advantages with use of bleach
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advantages with use of bleach

• 1. Chlorine in drinking water has prevented the
  spread of certain diseases
• 2. Bleaches have improved hygiene in the home
• 3. Bleaches have helped to improve the quality of
  food and clothes

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Problems with use of bleach
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Problems with use of bleach

• 1. Chlorine and sulphur dioxide are toxic

• 2. Household bleaches can harm the eyes and skin

• 3. Sulphur dioxide in food can cause severe
  breathing difficulties in some people

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SUMMARY
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• Action of chlorine bleach and sulphur dioxide on
  coloured substances

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THE END OF LESSON