CHEM 1110 1st Edition Lecture 14Outline of Last Lecture I. Enthalpies of reaction II. Calorimetry Outline of Current Lecture I. Characteristics of Gases II. Gas Pressure and its MeasurementIII. The Gas laws and Ideal Gas LawCurrent LectureI. Characteristics of Gases A. A gas is a physical state of an element or compound 1. Gases expand to fill the entire container they are placed in a. Move rapidly around container & exert force on its walls 2. Gases have low densities a. Thus they are easily compressed into smaller volumes 3. Gases (ideally) interact weakly with other gases and often are highly miscible (highly miscible)II. Gas Pressure and its MeasurementThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.A. Elemental gases1. He, Ne, Ar, Kr, Xe, and H2, O2, N2, F2, Cl2B. Selected common molecular gases1. CH4, NO2, N2O, CO, CO2, NH3, HCl, H2OC. Air (mixture)D. Atmospheric pressure: the weight of air per unit of area1. 1 atmE. Gravitational force (Pa): P=F/A= mass * acceleration/area1. 1 atm = 760 mm Hg = 760 torrF. Manometers1. The pressures of gases not open to the atmosphere are measured in a manometer2. A manometer consists of a bulb of gas attached to a U-tube containing Hg3. Typesa. Open i. Pgas= Patmii. Pgas<Patm: Pgas= Patm -∆hiii. Pgas>Patm: Pgas= Patm +∆hiv. When Pgas = 0 torr (mmHg) then ∆h=Patm = 760mmi. 0 torr= no gas molecules= a vacuum! b. Closed III. The Gas laws and Ideal Gas LawA. Boyle’s Law: Robert Boyle observed that trapped volumes of gas were compressed by adding Hg in the manometer (increasing delta h or external P). Preformed at constant T.1. At constant T, when Pgas↑ then Vgas↓2. PV= k (at constant) or V= k (1/P)B. Charles’ Gas Law: V vs. T at const P1. The volume of a fixed amount of gas at constant pressure is directly proportional to its absolute temperature2. V1/T1=V2/T2a. T in kalvins (K)C. Avogadro’s Law: V vs. n at const P, T1.V1/n1 =
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