all about gases advanced chemistry. demonstration #1 inflating a balloon inflating a balloon
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All About GasesAdvanced ChemistryDemonstration #1Inflating a BalloonInflating a BalloonDemonstration #2Imploding Soda Can
Demonstration #3Eggs in a Flask
Five Characteristics of GasesGases expand to fill their containersGases are fluid they flowGases have low density1/1000 the density of the equivalent liquid or solidGases are compressibleGases effuse and diffuse
Ideal GasesIdeal gases are imaginary gases that perfectly fit all of the assumptions of the kinetic molecular theory (KMT)Gases consist of tiny particles that are far apart relative to their size.Gas particles are in constant, rapid motion.They therefore possess kinetic energy, the energy of motionThere are no forces of attraction between gas particlesThe average kinetic energy of gas particles depends on temperature, not on the identity of the particle.
PressurePressure is the force created by the collisions of molecules with the walls of a containerUnitSymbolDefinition/RelationshipPascalPaSI pressure unit1 Pa = 1 newton/meter2Millimeter of mercurymm HgPressure that supports a 1 mm column of mercury in a barometerAtmosphereatmAverage atmospheric pressure at sea level and 0 C Torrtorr1 torr = 1 mm HgAn Early BarometerPressure is measured with a barometerThe normal pressure due to the atmosphere at sea level can support a column of mercury that is 760 mm high
Common Units for Pressure1 standard atmosphere (atm)= 101.3 kPa (kilopascals)= 14.7 lbs/in2= 760 mm Hg (millimeters of mercury)= 760 torrStandard Temperature and Pressure (STP) Often the volume of a gas is needed at standard conditionsFor scientists, this means STPStandard temperature is 273 KStandard pressure is 1atm
101.3 kPa = 1 atmosphere (atm) = 760 mm Hg = 29.92 inches Hg = 14.7 lbs/in2 (psi)
Gas Conversions Factors At STP conditions (0C, 1 atm):1 mole of any gas occupies 22.4 liters of space. Here are the conversion factors:1 mole= __________ particles= _____L (at STP)At SLC, standard lab conditions, (25C, 1 atm):1 mole of any gas occupies 24.5 L/mol. Here are the conversion factors:1 mole= __________ particles= _____L (at SLC)
6.02 x 102322.46.02 x 102324.5Gas Volume to Mole Sample ProblemConvert 3 moles of helium to liters (at STP)
Joseph Louis Gay-LussacAmadeo AvogadroRobert BoyleJacques CharlesThe Gas LawsWhen we make changes in a property of a gas, other properties change in a predictable wayLed to the creation of the Gas Laws Avogadros hypothesis states that ________ volumes of gases (under the same temp. and pressure conditions) contain _______ number of particles. If containers have the same ____, ____, and ___, then they will have the same ____ of particles regardless of the _________ of the gas particle. You might think that a small gas molecule would take up ______ space than a large gas molecule, but it ___________ at the same _________________ and ______________!! Avogadros Hypothesis
equalequal T P V#sizelessdoesnttemperaturepressureAvogadros LawVolume and MolesAs the # of gas particles increase, the volume of a flexible container will increase if the temperature and pressure of the container remain constantDIRECT relationshipExampleBlowing more air into a balloon makes it larger
# particles ___, V ___ Here is the qualitative relationship between the pressure, temperature, and volume of a constant # of gas particles in a container: (1) ___________ Law: At a constant temperature, as the volume of a container __________ the pressure of the container will ___________. V___, P ___ *Example: Compressing the gas in a flexible container will _________ its volume. Gas Laws
Pressure is inversely proportional to volume when temperature is held constant.
(2) ____________ Law: At a constant volume, as the temperature of a container __________ the pressure of the container will ___________. T___, P ___ *Example: Heating a rigid container causes the gas inside to move __________ which causes _________ pressure. Be careful! Too much heat will make it explode!Gas Laws (continued)PressureTemperature (K)
Guy-LussacsincreasesincreasefastermoreGay Lussacs Law
The pressure and temperature of a gas are directly related, provided that the volume remains constant.Temperature MUST be in KELVINS!
(3) ____________ Law: At a constant pressure, as the temperature of a container __________ the volume of the container will ___________. T___, V ___ *Examples: Heating a balloon will cause it to ___________. Taking a balloon outside on a cold winter day will cause it to _____________. If you could keep a gas from condensing, you could cool it off to absolute zero and the volume of the gas would be _________!Gas Laws (continued)
VolumeTemperature (K)CharlessincreasesincreaseinflateshrinkzeroCharless LawThe volume of a gas is directly proportional to temperature, and extrapolates to zero at zero Kelvin.(P = constant)
Temperature MUST be in KELVINS!
The Combined Gas Law This equation combines all of the previous three laws into one convenient form.Boyles Law: = constantGuy-Lussacs Law: = constantCharless Law: = constant V TP . TPxV = constantP . T V TPxV P1 x V1TK1P2 x V2TK2=(initial conditions) = (final conditions) Using the Combined Gas Law requires you to have the temperature in _____________ units. The pressure and volume units can be anything as long as the initial and final units are ______ __________.Kelvinthe sameThe Combined Gas LawThe combined gas law expresses the relationship between pressure, volume and temperature of a fixed amount of gas.
Combined Gas Law Sample ProblemA balloon at a pressure of 4.5 atmospheres, 300 K, and a volume of 35.0 liters is changed to STP conditions. What will the new volume of the balloon become?
The Ideal Gas Law An equation used to calculate the __________ of gas in a container (in units of _________.)
PV=nRTThe units for T= __________, V = _________, n = # of moles R = Ideal Gas Constant The value of R changes depending on the unit of ____________ used in the equation:R = 62.4 (mm Hg)(L)/(mole)(K) R = 8.31 (kPa)(L)/(mole)(K) R = 0.0821 (atm.)(L)/(mole)(K) R = 2.45 (in. Hg)(L)/(mole)(K)amountmolesKelvinLiterspressure The Ideal Gas LawPractice Problems: 6.5 moles of a gas has a pressure of 1.30 atmospheres and it has a temperature of 20Celsius. What is the volume of the gas?
2) How many moles of gas are there in a 7.3 liter balloon with a pressure of 1.11 atm and temperature of 395 K?( ) ( ) = ( ) ( ) ( )1.30V6.50.0821293 KV = 120 L( ) ( ) = ( ) ( ) ( )1.117.3n.0821395 Kn = 0.25 moles