Unit 33 Bleach Two common bleach

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Unit 33 Bleach Two common bleach
Unit 33 Bleach Oxidizing Cl2 and reducing
SO2/SO32-
Unit 33 Bleach How Cl2 or SO2 reacts with H2O
Unit 33 Bleach Test for Cl2 or SO2
Unit 33 Bleach ClO- will give Cl2
Unit 33 Bleach electrolysis of Brine
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Unit 33 Bleach Two common bleach
33.1Uses germicides 33.2Chlorine bleach sodium
hypochlorite(NaOCl) Prepared by 2NaOH Cl2
?NaOCl NaCl H2O 33.8Bleaching action dye
OCl- ? dyeO Cl- Sulphite bleach
SO32- 33.11Bleaching action dye SO32- ? dye
O SO42-
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• 2002 CE Q.7(b)
• Chlorine bleach can be made by reacting chlorine
  with sodium hydroxide solution.
• Write a chemical equation for the reaction.
• the reaction is known to be redox. State whether
  chlorine acts as an oxidizing agent, a reducing
  agent or both. Explain your answer in terms of
  the change in oxidation number.
• Apart from being used as a bleach, suggest ONE
  other use of chlorine.

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Unit 33 Bleach Oxidizing Cl2 and reducing
SO2/SO32-
33.7 Oxidizing properties of Cl2 Cl2 2Br- ?
2Cl- Br2 / Cl2 2I- ? 2Cl- I2 33.11 Reducing
properties of SO32- SO32- MnO4- ? SO32-
Cr2O72- ? SO32- Br2 ?
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Oxidizing properties of Cl2 (Cl2 ? Cl-) and
reducing properties of SO32- (SO32- ? SO42-)

• Equation can be balanced by atoms, charges and
  oxidation number change.
• Cl2 2I- ? 2Cl- I2
• Charge 2- Charge 2-

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Balanced by oxidation no. change
SO32- MnO42- ? SO32- Cr2O72- ? SO32- Br2 ?
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Unit 33 Bleach How Cl2 or SO2 reacts with H2O
33.7 Cl2(g) H2O(l) ? Cl-(aq) ClO-(aq)
2H(aq) Cl2(g) H2O(l) ? HCl (aq) HClO(aq)
33.11 SO2(g) H2O(l) ? SO32-(aq)
2H(aq) SO2(g) H2O(l) ? H2SO3(aq)
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Unit 33 Bleach Test for Cl2 or SO2
33.9 Cl2 turns moist blue litmus paper red
(acidic properties) and then white (bleaches
it). Cl2(g) H2O(l) ? Cl-(aq) ClO-(aq)
2H(aq) 33.12 SO2(g) turns moist dichromate
paper from orange to green. 3SO32- Cr2O72- 8
H? 3SO42- 2Cr3 4H2O
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Unit 33 Bleach ClO- will give Cl2
33.14 Cl-(aq) ClO-(aq) 2H(aq) ? Cl2(g)
H2O(l)
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Unit 33 Bleach 33.3 electrolysis of Brine
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Unit 33 Bleach 33.3 electrolysis of Brine
Avoid direct reactions H2 Cl2 ? 2HCl Cl2
2NaOH ?NaCl NaOClH2O H2, Cl2 and NaOH must be
separated.