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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
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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) • 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 water Na+(aq) + ClO-(aq)
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 • photography • germicides • hair bleaching • batteries • biochemical reactions • In bleaching, the bleach is an oxidizing agent and the stain is a reducing agent