04CHM114_0225

04CHM114_0225 - CHEM 114 Spring 2004 Wednesday, Feb. 25th...

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Unformatted text preview: CHEM 114 Spring 2004 Wednesday, Feb. 25th Lecture No. 15 Wind-up of last day: Basic oxides; give hydroxides with water. Hydroxides of alkali metals are the common bases. _ 0 Turn litmus paper blue. (Demo Na in water plus litmus) o neutralize acids (Demo) Acidic oxides: give protic oxyacids with water (the strongest acids are those formed from the non-metals in their highest oxidation states). . .. HNO3, H2804, HClO4 (why? later, maybe). Basic oxides: give hydroxides with water 2Na +1/2o2 _.9 Na.‘ 0 Ho. ou *H-avo —- “4.1;? Hf“) Acidic oxides: give protic oxyacids with water (the strongest acids are those formed - from the non-metals in their highest oxidation states). 303 + H20 —t- waou ‘ Shoo-s Lad predict acidity of HZSeO4 etc 5+ sozvsso3 90,, 4, he .—-, HJO: out: N205 +5» 42*“; v “Mu 5°: 5‘ t . ‘ Demo P205” fiercest dehydrating agentc. '5 I,; J K” .. Avie, he -9 “30* (kl-In“ 2 a, so, Amphoteric oxides —- CA s... - _ a: «a u “a H 5‘4- 1 m. 3...}. . 2;; + "‘ “‘ A" 2"“ f'fi‘¢ 1kg fiL+‘.*1 I “.1: ‘5 ‘F I Group operties (section 7.7) (e.g. alkali metals, alkaline earth metals, non-metals, hydrides, halogens etc. . ..) drop out for now... more important things to do. CHAPTER 8. CHEMICAL BONDING. Mostly to do with the stability of szp‘S octets. Basic ideas, and extreme cases. 1. Ionic bonding occurs when electrons get transferred from one atom to another in order to form complete szpfI octets. Ma) - XI‘J) "‘ Mu" *xzh and then the ions stick together by charge—charge attraction '5 II- Q "’ m + x —. M x (.5) t” r.) . ‘.h par itch-own: Finally ion pairs condense to give ionic solid. “ha-cu) % M""" (.6) auto-qu. mu. wt: emu-3H m ‘ a: fun... Shortly we’ll consider the steps to . fl. 3 3, formation and the energies involved. Jul... 4 m. Par: covalent Bonding occurs because electrons get shared, again so as to give each bonded species a "closed shell” e.g. H-H (H2) O=C=O (C02) S2 SZPG Conceptual aids: . Lewis electron dot representations of Valence electrons and of chemical processes, using the octet rule. Li .N. A]. H- .'Si- Use the concept: 1. Ionic bonding: Na.I + = [Na ]+ [:qu pa. 33").‘1‘3‘ 3" 2. Covalent bonding: I I .0 (l. g‘ o o : 5:1- + .0: = : I. . . ’ ‘1’ t J’r‘ 5 P DETAILED TREATMENT 1. Ionic bonding: and ionic solids — the steps to formation and the energies involved. (i) make sodium ions from atoms Na(g') = Na+ (g) + e' Energy change: AH = ionizationj energy = 496 kJ/mol (endothermic .... ..absorbs energy) Which of the following is not an endothermic process? A. boiling of water B. ionization of hydrogen C. burning of magnesium strips. etc (ii) make chloride ions from chlorine atoms Cl(g) + e- —) Cl-(g) Energy change: AH = electron affinity = -349 kJ/mol Total 496-349 is positive.... unfavorable 1:01:59 In 3 i E (iii) bring ions together by coulomb (charge-unlike charge) attraction (Eq. 8.4) (a) to form an ion pair Na+Cl' (looks like molecule Equation: N .. r.) «- u-cu -.» Net" C.» I."- fit? AH = -340 kJ/mole (b) bring ion pairs together to form a crystal lattice Equation: Natu- "’ Fit-“C “5"”; Now energy change is large negative: Na+ (g) + Cl' (g) 9 NaCl (crystal) AH = -788 kJ/mol “‘fi 7 ...
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This note was uploaded on 11/01/2009 for the course CHM 114 taught by Professor Aksyonov during the Fall '08 term at ASU.

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04CHM114_0225 - CHEM 114 Spring 2004 Wednesday, Feb. 25th...

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