04CHM114_04_130

04CHM114_04_130 - Din/Quad] CHEM 114A Spring 2004 Fri. Jan....

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Unformatted text preview: Din/Quad] CHEM 114A Spring 2004 Fri. Jan. 30":l 2004 Lecture No. 5 website www.public.asu.edu/~caangell The MOLE (cont’d) So the MOLAR volume of water (density 1 g/ml) is the volume occupied by Avogadro’s number of water molecules. It is 18 ml, because one mole of water weighs 18 g, and each g occupies 1 ml. (density of water is 1 g/ml) Continuing, all atomic weights are the masses of Avogadro’s number of the atoms in question (which will have a fixed distribution of isotopes because of the way the earth was formed) expressed without units (they are written without units because of the way they are defined relative to the mass of the standard 12C). Another example: Heat of formation of oxygen atoms from oxygen molecules, expressed by the chemical process 0.1.9) —-v 20(3) AR \S Meluu- Jam—«3n, will be tabulated infies per mole of oxygen decomposed. AH = 247.5 kJ/mol 02 (see appendix C) The energy of ionization of sodium will likewise be tabulated in the energy needed to remove one mole of electrons from one mole of Na atoms. (107 .7 kJ/mol) Nam—a Ham) 1- e" as : te7'7as/Mse OK. . .. Ready for Chapter 4.. reactions in solutions — AQUEOUS SOLUTIONS Chapter 4- (Mans (in Aqueous solutions) Chemistry is mostly about changing substances from one form to another. A lot of the time this happens in a liquid medium consisting mostly of water —— i.e. in aqueous solutions. Solution: what is a solution? A homogeneous mixture, on the size scale of molecules, involving two or more substances. You make a solution by “dissolving” the “solu ” in the “solvent”. (Solute is the minority “component”, i.e. the chemical substance of which the number of moles is the smallest) . Example: salt one mole, water 99 moles... composition of solution is 1 mole % salt!!! Some aqueous solutions conduct electricity, others do not. The ones that do are called “electrolyte solutions” (you saw it with your own eyes) Example of an electrolyte solution: NaCl or sulfuric acid in water “1.50.4 -t- HvD =§ H30?#H$09- Hydronium ion o 4::- fifl Examples of non-electrolyte solutions: 1. sugar in water, 2. Alcohol in water, etc (the solute doesn’t have to be a solid like sugar) . No charged particles are formed. e. g. Methanol: HOH group interacts with OH’s of water can; set We?“ Electrolytes: Strong vs weak (DEMO) p a £1. a A L W' cugcoeH + the -—e , Wu-I: Joke . . gt“ ‘3 OK. let s have some reactions 1n aqueous solutro . H 3 6-1 ) 4.2 Precipitation reactions. m fut}! WWQGW \:~. {film-+th What is a precipitate? Examples: 1. a halide PbIZ, 2. an oxy salt CaCO3 (limestone), as (M:- lM) + Ne-«QMCMJ Q Ga I41: 2N6: Qt; SOLUBILITY: concept C6; 3 if Solubility rules: . All nitrates, acetates go I“ u M W‘rh _. .. '= — 9 ~63 Most: halides, sulfates 5% IA sis—(LR D a Important exceptions: sulfates of alkaline? earths where the cations are large and just balance the Ionic equations: EXCHANGE REACTIONS: Some that precipitate: A different sort of a precipitation: the release of gases: (it’s the gas that is insoluble in water) Na2C03 + HCl —) NaCI + H10 + C02(g) Macaoats) + am CM) a? meat“) a 64w + carts; Some (exchange reactions) that just change color in solution: Gamma) + Na; ea ngalé 4.3 ACID-BASE REACTIONS: What is an acid? Q; We geeks 595% 5; E h {6939: ‘ @H‘a‘esa H'efié' “law 5% H394? we Céfi Whatisabase? A kafimae: M afiffig‘ks praising; “i=9 firm 44%:9 Na 9% a 0%” e? at as he What happens when they come together? Forming salts and water “MIA; Us a. Hamlin-v ba-J'eé Nfiuag as a. Week beak” 4.4 QXJDATION-REDUCTIQE REACTIONS: A very important class of reaction that produces a lot of energy. . .. Electrons get transferred First concept to get is 9311333 ION 1. For ions: {the charge on the ion) Ca Cage; C&;* °¥tdeesleeL.Ne Q ecsle t8 #2; $3: Nuts. New :3 =H gag, ‘3. . RED-OX reaction involving formation of ions: ‘ g Ca +1/202 -) CaO Ca 2* with 02' d a i E...- =5 0 . O o «g- 1 L 2. For elements in molecules: e. g. for carbon in - CO vs carbon in C02 The oxidation number is the apparent charge when the electrons in the bonds are assigned to the partners according to certain rules. Rule 110. 1: Oxygen is always —2, Fluorine always —1 Rule No. 2: alkali metals always +1, alkaline earth metals always +2 Rule No 3: elements always have O.N. zero Rule No. 4. The sum of the oxidation numbers of the elements in a neutral compound must be zero Apply to carbon monoxide CO “fame: t. MN be (a! 6 AC 1"“?- 7 Apply to CO2 9 =' L T5“; =- '1 ll 1. n C Musk be: deb} : -9 Sodium phosphate vs sodium phosphite N91 "*Vh-l — G o 'I c ‘ ‘ P a 'fi‘ 3 mo. air-u a 3:. 9 +3" (3+9 he Magus-st) Uncertain cases: e.g. CH4 how do we decide which element “gets” the electrons? (we have to look up a table of “electronegativities” and give the electrons to the most electronegative element) Rule for hydrogen: +1 with nonmetals -1 with metals Apply to LiCoO2 (reactive component of cathode in the lithium battery) Battery power comes from redox reaction U cathode Li + C002 -) LiC002 (high e— pressure) think of it electrolyte as electrons falling downhill or going from high pressure to low anode DU ...
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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_04_130 - Din/Quad] CHEM 114A Spring 2004 Fri. Jan....

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