21 - Chemistry 1000 Lecture 21: The halogens Marc R....

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Chemistry 1000 Lecture 21: The halogens Marc R. Roussel
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The halogens I Group 17 I Pure elements consist of X 2 molecules I All form - 1 anions I States and colors at room temperature: F 2 Cl 2 Br 2 I 2 gas gas liquid solid yellow yellow-green dark red dark violet
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I Reduction potentials range from extremely to moderately positive, i.e. these are good to excellent oxidizing agents: X 2 + 2e - 2X - (aq) Element F 2 Cl 2 Br 2 I 2 E / V 2.866 1.358 1.065 0.535 I In nature, always found as the anion, except iodine which is also found in some oxoanions I Fluorine in particular can often oxidize elements with very high electronegativities (e.g. chlorine, oxygen).
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Disproportionation I The pure halogens are often unpleasant to use. I Solutions in water are often used as oxidizing agents (“chlorine water” and “bromine water” especially, but no equivalent for fluorine). X 2(aq) + H 2 O (l) ± H + (aq) + X - (aq) + HOX (aq) HOCl is hypochlorous acid. I This process is more favorable in base: X 2(aq) + 2OH - (aq) ± X - (aq) + OX - (aq) + H 2 O (l) OCl - is the hypochlorite ion and is the oxidizing agent in household bleach.
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This note was uploaded on 03/03/2012 for the course CHEM 1000 taught by Professor Marc during the Fall '06 term at Lethbridge College.

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21 - Chemistry 1000 Lecture 21: The halogens Marc R....

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