04CHM114_0202

04CHM114_0202 - 6CHEM 114A Spring 2004 Mon Feb 2nd 2004...

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Unformatted text preview: 6CHEM 114A Spring 2004 Mon. Feb 2nd 2004 Lecture No. 6 website www.publicasu.edu/~caangell Ch. 4 Reactions in Solutions (cont’d) 4.4 OXIDATION-REDUCTION REACTIONS: Oxidation numbers (cont’d) Uncertain cases: e. g. CH4 how do we decide which element “gets” the electrons? (we have to look up a table of “electronegativities’find give the electrons to the most electronegative element) "P “3'61- Rule for hydrogen: +1 with nonmetals ——1 with metals Apply to LiCoO2 (reactive component of cathode in the. lithium battery) Battery power comes from redoeracti In Li + C002 -.‘> LiCoO2 (high 6- pressure) think of it electrolyte as electrons falling downhill at. or going from high pressure to low Chemical energy for power comes from redox reactions: fl e.g. internal combustion engine: octane + oxygen 9 carbon dioxide + water + (energy released for work) 1. hydrogen doesn’t change (+1 in both octane and water) 2. oxygen changes from 0 to —2. 1. Carbon changes from —4 to +4 IQ Release of energy as HEAT in combustion reactions (Studied in next chapter — Thermochemistry) As ELECTRICAL ENERGY in case of reactions carried out in cells (much more desirable) Oxidation of metals by acids (Displacement reactions) Mg, Al, Zn etc (hydrogen displaced) \ M5. + M" CLCCM) -I M: *C‘H) «- 2.6: Na (even water acts as an acid 4' H‘, T Gold Au. No reaction FOR METALS. ACTIVITY SERIES see Table 4.5 ACTIVITY SERIES see Table 4.5 Li Highest electron “pressure” K Ba Ca Na Mg A1 211 Fe Ni Pb Hydrogen Au (lowest electron pressure) Relation of activity series to electrochemical cell voltage. 31.. Au?” .4 3L:* +Au MM OMIT CHEMICAL ANALYSIS Chapter. 5 Thermochemistry .... .. Here we learn about the first law of thermodynamics. . ...conservation of energy, and the relation between heat and work.. ..Engineers need to know it!! Forms of Energy Potential Lug-g 3 $3 V‘F'h'" 'F P‘sdun ‘ so (+91“; , Kinetic Q on... mu) ——I’ Heat energy (random kinetic energy) Inter-Conversion of energy (energy Quality) Potential to kinetic and back again in a swinging pendulum. Stop pendulum at the bottom suddenly... what happens to the energy?. It is converted to heat and then is difficult to recover. Conversion of heat . into work (as in a steam engine) is subject to efficiency limits. .. only 100% efficient at the absolute zero of temperature (0 K).. . but that's for a Thermodynamics course.. Here we only deal with the easy parts. First: define terms the small part of the universe in which we are interested. consider it separated from the rest, as in a piston, but in communication in some ways e.g. 1. volume can change by means of piston movement. .. no change of matter possible. This is called a "closed" fl system "In (‘35-'- fl. h Micah: 2. Heat MAY be allowed to flow in and out to keep the system at same temperature. (ISOTHERMAL system and a process occurring at constant temperature is called an ISOTHERMAL process.) 3. Heat changes may be forbidden, e.g. by placing the system 1-“ ' .l' '- in a "thermos" flask. Ideally no heat can flow in or out. Such a M ‘ . I fl systems is called an ADIABATIC system. A process occurring in a thermos flasE'ls called an ADIABATIC process. This means a description of what states of matter are present, how many different phases are in equilibrium, one or more, and what their compositions are if it is a multicomponent system. EQUATION OF STATE ( e.g. PV = NRT, Van der Waals eq) H fl Thermodynamic properties. Extensive vs intensive properties. V, H, E, and, a " A later, S, G) Change of enthalpy with T properties like density, (dm/dV), V, H, E, S, G are all STATE properties.. what f" does it mean? ' 1".) Ft Paonar v w mt UAW: bet-Inns on“ w P “1' If“ t feud “0 ' 'r m . k‘ 0" Swgbt‘fasq REVERSIBLE AND IRREVERSIBLE PROCESSES Changes in state properties AV, AE, AH —— e U.) E 4‘ «T HEAT, WORK, AND THE FIRST LAW OF THERMODYNAMICS W Work and conversion of work into heat Count Rumsford and the cannons 1 cal = 4.18] Work work: forcexdistance w ‘3 F X L a...» j: 4......} v 3 9‘: F4, :46 but pressure = force larea, so ‘I P X A V work = pressure x change in volume = -PAV if system expands or PAV (positive) if system is compressed (work done on system) FIRST LAW of thermo summarizes experience that a system's energycan be changed by either "flowing heat into" or "doing work on” the system, and that the change in energy is always the sum of the two AE=q+W hey!- Gun-K 0-4441 Jun- fi Oh J‘ ‘M l, 10 ...
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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_0202 - 6CHEM 114A Spring 2004 Mon Feb 2nd 2004...

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