Transcript Collapsing Can

Preparation of Chlorine
Gas from Bleach
When bleach is treated with an acid, evolution
of chlorine gas ensues
Demonstration
 The evolution of chlorine gas was rapid
in the presence of acid
 Chlorine gas was unable to be collected
“over water” like oxygen gas since
chlorine gas will react with water
 Chlorine reacted with the red dye in the
paper, bleaching it to a lighter color
Purpose
 To prepare chlorine gas
 To collect chlorine gas by upward
displacement of air
 To demonstrate the presence of
chlorine gas
Concepts
1.
Bleach
2.
Redox Reactions
3.
Oxidizing Agents
1. Bleach
 Commercial laundry bleach is a solution of
sodium hypochlorite in water
NaClO(s) water
+
-
Na (aq) + ClO (aq)
 When dissolved in water the sodium
hypochlorite dissociates into hydrated sodium
and hydrated chlorite ions
 The hypochlorite ion is responsible for laundry
bleaching: it gobbles up electrons
2. Redox Reactions
 In a redox reaction, one substance loses
electrons while another substance gains
electrons
 “Redox” is a conventional term which is a
combination of the words “reduction” AND
“oxidation”
 The substance that loses electrons is said to be
oxidized and/or the reducing agent
 The substance that gains electrons is said to be
reduced and/or the oxidizing agent
3. Oxidizing Agents
 Oxidizing agents have many uses
 bleaches: hypochlorite
 batteries: zinc and sulfuric acid
 antiseptics: hydrogen peroxide
 Oxidizing agents work by gaining
electrons from other substances
 and/or
donating oxygen to other
substances
Conclusions
 When hypochlorite bleaches
something, its chlorine atoms are
being reduced to chloride ions
 The hypochlorite in bleach can be
rapidly decomposed in the
presence of an acid
 Chlorine gas is the product of the
decomposition of hypochlorite ion
Comments
 Redox reactions are extremely common
chemical reactions
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photography
germicides
hair bleaching
batteries
biochemical reactions
 In bleaching, the bleach is an oxidizing
agent and the stain is a reducing agent