CHEM 101 1st Edition Lecture 23Outline of Last Lecture I. Theories of Chemical BondingII. Valence Bond TheoryIII. Molecular Orbital TheoryOutline of Current Lecture I. Molecular Orbital Theory (cont.)II. Gas PropertiesIII. Boyle’s LawIV. Charles’ LawV. Avogadro’s HypothesisCurrent Lecture- Molecular Orbital Theory (cont.)o The order of bonding is as follows: σ2s σ *2s π2p σ2p π*2p σ *2pChapter 10: gases and Their Properties- Gas Propertieso Gas properties are characterized by the following quantities: Pressure Volume (liters; L) Temperature (Kelvin; K) Number of particles (moles; Mol)- Gas Pressureo The atmospheric pressure of air is measured with a device called a barometer: (Evangelista Torricelli; 1643)o Pressure is the force exerted on an object divided by the area over which the force is exertedP= force = m x g = d x V x g = g x d x harea area areawhere m is mass g is gravity (9.8 N/kg) (1 N = kg x m)h is heightd is densityo The pressure is proportional to the density and the height of a column of a givensubstance: P = g x d x ho Common pressure units 1 standard atmosphere (1 atm)=760 mm Hg or Torr (exactly) SI unit of pressure 1 pascal (Pa) = 1 newton (N)/square meter (m^(2))*more common than a is kPa: 1 kPa = 1000 Pa Standard Atmospheric pressure conditions:1 atm = 760 Torr = 101.325 kPa = 1.01325 bar- Why is mercury used for a barometer?o h = P s g x d where P = 101325 Pag = 9.8 N/kgd(Hg)= 13.53 g/cm^(3)h= 101325 f 9.8 N x 13.52 g x 1 kg x 10^(6) cm^(3) kg cm^(3) 1000 g 1 m^(3)= 0.76- The relation between pressure and volume is inversely correlated (as one increases the other decreases)- Boyle’s Lawo Robert Boyle:P (proportional to) 1 VP = CB x 1 P x V x CB VP1 x V1 = P2 x V2(if n and T are constant) - Charles’s Lawo Relation between temperature and volume: Volumes become smaller by decreasing the temperature Volumes become larger by increasing the temperatureo Absolute zero = -273.15 °Co Jacques Charles:V (proportional to) TV = CC x T CC = V TV 1 = V 2T1 T2(if n and P are constant) - Avogadro’s Hypothesiso Amedeo Avogadro and Joseph Gay Lussac: Equal volumes of gases under the same conditions of temperature and pressure have equal numbers of particlesV (proportional to) n Ex: 2 NaN3(s) 2 Na(s) + 3N2(g)- The Idea Gas Lawo Boyle’s Law: V (proportional to) 1/P (constant n, T)o Charle’s Law: V (proportional to) T (constant n, P)o Avogadro’s Hypothesis: V (proportional to) n (constant T, P) V (proportional to) n x T V = R (n x T/P) P P x V = n x R x T The Idea Gas LawR = P x V (under standard temp and pressure conditions) n x T Where V= 22.414 LR = (101325 N/m^(2)) x (22.414 L) x (1 m^(3)/L) 1 mol x 273.15 KR = (101325 J) x (22.414 L) x (1 m^(3)/L) 1 mol x 273.15 KR = 8.314 J/K x mol P x V – n x R x TMW = m/n n = m/MWP x V = (m/MW) x R x T MW x P = (m/V) x R x Tm/V = (MW x P/ R x T) d = (MW x P/ R x
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