chem 6c notes

chem 6c notes - First lecture after exam 2 Friday May 9,...

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First lecture after exam 2 Friday May 9, 2008 23-1 Noble Gases     Initially thought to be chemically inert. Pauling predicted reactivity of xenon o XeF2, XeF4, XeOF2, XeF6, XeO4, and H4XeO6 XeF2 (aq) + 2H+ + 2e- YIELDS Xe(g) +2HF (aq)…. . E*= +2.64V Xenon and Fluorine Xe + F2  when mixed 2:1 gives XeF2, When mixed 1:5 gives XeF4 When mixed 1:20 XeF6 23-2 Group 17: The Halogens     Diatomic molecules symbolized by X2 Melting and boiling points increase as you go down the GROUP Reactivity decreases down the GROUP Fluorine Most electronegative element Forms strong ionic and covalent bonds Production and uses of halogens Chlorine and fluorine o By electrolysis
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2 HF YIELDS H2 + F2 Bromine Seawater is 70 ppm Br- acidify and oxidize with Cl2 CL2 + 2Br- YIELDS 2 Cl- + Br2…. E*cell= .293 volts Iodine Also obtained from inland brines and certain sea plants NaIO3 is found in large deposits in Chile o Usually reduced with bisulfite. Many useful compounds can be formed from halogens. Hydrogen Halides CaF2 + H2SO4 YIELDS CaSO4 +2HF H2 + X2 Yields 2 HX TABLE 23.3 FREE ENERGY OF FORMATION OF HYDROGEN HALIDES @  298K in  DELTA G*formation  in Kj/Mol HF…. . -273.2 HCl…. .-95.30 HBr….-53.45 HI…….+1.70 Perchloric Acid HClO4…. Oxidation states of halogens. Start with +1 on HOCl… just keep  adding a double bonded oxygen to give you +3, then +4 then +7 at HCL04 Hypochlorite, OCl- (linear) Chlorite, ClO2- (angular)
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Chlorate, ClO3- (trigonal pyramidal) Perchlorate ClO4- (tetrahedral) Structures of Interhalogen Compounds XY- linear XY3- t shaped XY5- square pyramidal Polyhalide Ions I3- o Lewis structure shows middle Iodine with 10 electons o It is the only element that can do this.  I3- is an excellent source of I2, if you don’t want to use elemental  iodine for a reaction you use I3-
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chemistry 6c notes Monday, May 12 23-3 Group 16: The Oxygen family S and O are clearly nonmetallic in behavior Similar compounds: o H2S and H2O, CS2 and CO2, SCl2 and CL2O Important Differences o Due to properties and characteristics of Oxygen. Small size, high electronegativity and inability to employ an  expanded valence shell. Hydrogen bonding in water but NOT in H2S Oxidation State of Oxygen (O) is -2,-1 and 0 But oxidation state of Sulfur (s) -2 to +6 inclusive. Sulfur is a yellow solid at room temperature, and depending on how its 
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This note was uploaded on 04/14/2009 for the course CHEM CHEM 6C taught by Professor Hoeger during the Spring '08 term at UCSD.

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chem 6c notes - First lecture after exam 2 Friday May 9,...

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