Chem Notes week 13
Chem Notes week 13 CHE 106 - M001
Popular in General Chemistry Lecture I
CHE 106 - M001
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This 3 page Class Notes was uploaded by Andrea Scota on Sunday December 6, 2015. The Class Notes belongs to CHE 106 - M001 at Syracuse University taught by R. Doyle in Fall 2015. Since its upload, it has received 28 views. For similar materials see General Chemistry Lecture I in Chemistry at Syracuse University.
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Date Created: 12/06/15
Pink- mentioned in class Chem Notes Week 13 TEXTBOOK CHAPTER 10 (Sections 10.1-10.4) Gases Characteristics of Gases (10.1) Substances that are gases at room temp tend to be molecular substances with low molar masses Air is a mixture of mainly N 2nd O an2 is the most common gas we encounter here on Earth Vapors are liquids and solids that can also exist in the gas state Gases are compressible Gases mix in all proportions because their component molecules are so far apart Pressure (10.2) Pressure conveys the idea of force, a push that tends to move something- in science, pressure (P) is the force, F, that acts on a given area, A. o P = F/A To describe the state or condition of a gas, we must specify three other variables besides P: volume (V), temperature (T), and quantity (n). Volume is usually measured in liters, temperature in Kelvin, and quantity of a gas in moles. o Pressure is the force per unit area o Measured in the SI unit, pascals, Pa (1 Pa = 1 N/m ) 2 Named for Blaise Pascal 5 5 2 o The bar is another related unit: 1 bar = 10 Pa = 10 N/m A barometer is used to measure the pressure of the atmosphere Standard atmospheric pressure: corresponds to the typical pressure at sea level o Use to express gas pressure, such at the atmosphere (atm) and the millimeter of mercury (mm Hg), called the torr. 1 torr = 1 mm Hg 5 Also, 1 mm Hg = 1.01325 x 10 Pa Thus, 1 atm = 760 mm Hg = 760 torr = 1.01325 x 10 Pa 5 = 1.01325 bar Manometers are commonly used to measure the pressure of an enclosed gas The Gas Laws (10.3) There are several simple gas laws Boyles Law: the volume of a fixed quantity of gas maintained at constant temperature is inversely proportional to the pressure (one gets smaller as the other gets larger) o V = constant x (1/p) OR PV= constant o P x V = P x V f f i i o Value of the constant depends on the temperature and amount of gas in sample o Boyle’s law is important to scientific history because is was the first to carry out experiments in which one variable was symmetrically changed to determine the effect on another value Charles’s Law: the volume of a fixed amount of gas maintained at constant pressure is directly proportional to its absolute temperature o V/T = constant Avogadro’s Hypothesis: equal volumes of gases at the same temperature and pressure contain equal numbers of molecules Avogadro’s Law: the volume of a gas maintained at constant temperature and pressure is directly proportional to the number of moles of the gas o V/n = constant o n is the number of moles o For instance, doubling the number of moles of gas causes the volume to double if T and P stay the same Each gas law is a special case of the ideal gas equation The Ideal Gas Equation (10.4) We can combine Boyle’s Law, Charles’s Law, and Avogadro’s Law into a general gas law known as the ideal gas law. o Ideal gas: hypothetical gas whose pressure, volume, and temperature relationships are described completely by the ideal-gas equation o PV = nRT o R is known as the gas constant and depends on the units of P, V, n, and T. But is most commonly known in this chapter as R = 0.08206 L-atm/mol-K because pressure is most commonly given in atmospheres o The volume of one mole of gas is the molar gas volume, V m We can use the ideal gas equation to calculate variations in one variable when one or more of the others are changed Most gases at pressures less than 10 atm and temperatures near 273 K and above obey the ideal gas law reasonably well The conditions of 273 K (0 C) and 1 atm are known as the standard temperature and pressure (STP) In all applications of the ideal-gas equation we must remember to convert temperatures to the absolute temperature scale (kelvin scale)