Principles of Chemistry I
Principles of Chemistry I CHEM 1211
Popular in Course
Popular in Chemistry
This 5 page Class Notes was uploaded by Vesta Rippin on Monday October 12, 2015. The Class Notes belongs to CHEM 1211 at Georgia College & State University taught by Ronald Fietkau in Fall. Since its upload, it has received 19 views. For similar materials see /class/221957/chem-1211-georgia-college-state-university in Chemistry at Georgia College & State University.
Reviews for Principles of Chemistry I
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 10/12/15
CHEM 1211 Principles of Chemistry I Chapter 5 Gases O matter exist in three distinct physical states gas liquid and solid 0 relatively few substances exist in the gaseous state under typical conditions 51 Pressure 0 a gas 0 1 uniformly lls any container 0 2 is easily compressed and O 3 mixes completely with any other gas 0 one of the most obvious properties of a gas is that it exerts pressure on its surroundings eg when you blow up a balloon the air inside pushes against the elastic sides of the balloon and keeps it rm 0 see Figure 51 O a device to measure atmospheric pressure the barometer was invented in 1643 by an Italian scientist named Evangelista Torricelli 16081647 who had been a student of Galileo 0 see Figure 52 O at sea level the height of the mercury in the column is 760 mm 0 atmospheric pressure results from the mass of the air being pulled toward the center of the earth by gravity in other words it results from the weight of the air 0 low pressure is often associated with a storm high pressure with good weather 0 atmospheric pressure varies with altitude column of mercury only 520 mm high in Breckinridge Colorado because the air is thinner ie there is less air pushing down on the earth s surface at Breckinridge than at sea level 0 read about Otto von Guericke marginal note Units 0f Pressure 0 760 mm Hg 760 torr 1 atm standard atmosphere 0 however since pressure is defined as force per unit area the fundamental units of pressure involve units of force divided by units of area 0 in the SI system the unit of force is the newton N and the unit of area is meters squared m2 thus the unit of pressure is Nm2 and is called the pascal Pa O 1 atm 760 mm Hg 760 torr 101325 Pa 2992 in Hg 147 llbin2 be able to convert between torr and atm RFGCSU Page 1 of 6 Ch 05 Zumdahl 7th edwpd 52 The Gas Laws of Boyle Charles and Avogadro Boyle s Law the rst quatitative experiments on gases were performed by an Irish chemist Robert Boyle 16271691 0 see Table 51 0 see Figure 55 O conclude that PV k called Boyle s law where P is pressure V is volume and k is a constant for a given sample of air at a specific temperature 100 mL P 760 mm Hg 1 atm 50 1520 2 atm 333 2280 3 atm Boyle s law holds precisely only at very low pressures measurements at higher pressures reveal that PV is not constant but varies as the pressure is varied results for several gases at pressures below 1 atm are shown in Figure 56 since PV K then PlV1 k P2V2 where 1 and 2 represent two states conditions Charles s Law in the century following Boyle s ndings scientists continued to study the properties of gases one was French physicist Jacques Charles 17461823 who was the rst person to ll a balloon with hydrogen gas and who made the rst solo balloon ight 0 Charles found in 1787 that the volume of a gas at constant pressure increases linearly with the temperature of the gas see Figure 58 see Figure 59 note Kelvin temperature scale Charles s law can be written as V bT where T is in Kelvins and b is a proportionality constant 0 note 0 K is called absolute zero where theoretically the volume of a gas is zero since V bT can be rearranged to VT b then can write VlT1 b VzT2 Avogadro s Law 0 in 1811 the Italian chemist Avogadro postulated that equal volumes of gases at the same temperature and pressure contain the same number of particles this observation known as Avogadro s law 0 see Figure 510 0 stated mathematically V an where V is the volume of the gas 11 is the number of gas particles and a is a proportionality constant 0 for a gas at constant temperature and pressure the volume is directly proportional to the number of moles of gas obeyed by gas at low pressures RFGCSU Page 2 of 6 Ch 05 Zumdahl 7th edwpd 53 The Ideal Gas Law 0 we have considered three laws that describe the behavior of gases as revealed by experimental observations Boyle s law Charles s law Avogadro s law 0 the three relationships can be combined to give V RTnP where R is the combined proportionality constant called the universal gas constant 0 when the pressure is expressed in atmospheres and the volume in liters R has the value 008206 L atmK mol O the equation can be rearranged to give the familiar form of the ideal gas law PV nRT 54 Gas Stoichiometry 0 one mole of an ideal gas at 0 C 27315 K and 1 atm has a volume of 2242 L known as the molar volume 0 see Table 52 O the condition 0 C and 1 atm is called standard temperature and pressure STP Molar Mass 0fa Gas 0 one use of the ideal gas law is in the calculation of the molar mass molecular weight of a gas from its measured density 0 the equation is molar mass dRTP where d is the density see text for derivation 55 Dalton s Law of Partial Pressures 0 among the experiments that led John Dalton to propose the atomic theory were his studies of mixtures of gases 0 in 1803 Dalton summarized his observations a follows for a mixture of gases in a container the total pressure exerted is the sum of the pressures that each gas would exert if it were alone this statement known as Dalton s law of partial pressures can be expressed as follows P total O that is the total pressure is simply the sum of the partial pressures of the individual gases in the container 0 for a mixture of ideal gases it is the total number of moles of particles that is important 0 the fact that the pressure exerted by an ideal gas is not affected by the identity composition of the gas particles reveals two things about ideal gases 0 1 the volume of the individual gas particle must not be important and O 2 the forces among the particles must not be important 0 need to define mole fraction the ratio of the number of moles of a given component in a mixture to the total number of moles in the mixture 0 the Greek lowercase letter chi x is used as the symbol for mole fraction RFGCSU Page3 of 6 Ch 05 Zumdahl 7th edwpd 0 see Figure 513 experiment to determine amount of gas produced keep in mind the collected gas also contains water vapor 56 The Kinetic Molecular Theory of Gases 0 time to construct a model to explain the behavior of gases 0 the kinetic molecular theory KMT is a simple model that attempts to explain the properties of an ideal gas 0 read the postulates of the KMT found in the text 0 the molecules in a real gas have finite volumes and do exert forces on each other thus real gases do not conform to these assumptions 0 the theory is a good approximation of What happens Pressure and Volume Boyle s Law 0 pressure is inversely proportional to volume if the number of moles and the temperature are held constant Pressure and Temperature 0 pressure is directly proportional to temperature if the number of moles and the volume are held constant Volume and Temperature 0 volume is directly proportional to temperature if the number of moles and the pressure are held constant Volume and Number of Moles Avogadro s Law 0 volume is directly proportional to the number of moles if the pressure and temperature are held constant Mixture of Gases Dalton s Law 0 the total pressure exerted by a mixture of gases is the sum of the pressures of the individual gases is expected because the KMT assures that all gas particles are independent of each other and that the volumes of the individual particles are unimportant identities of the gas particles do not matter Deriving the Ideal Gas Law 0 see Appendix 2 RFGCSU Page4of 6 Ch 05 Zumdahl 7th edwpd The Meaning of Temperature 0 the Kelvin temperature is an index of the random motions of the particles of a gas with higher temperature meaning greater motion Root Mean Square Velocity O in the equation from the kinetic molecular theory the average velocity of the gas particles is a special kind of average 0 if the path of a particular gas particle could be monitored it would look very erratic see Figure 519 O the average distance a particle travels between collision in a particular gas sample is called the mean quotee path typically a small distance 1gtlt10 7 m for 02 at STP 0 see Figure 520 0 see Figure 521 57 Effusion and Diffusion O diffusion is the term used to describe the mixing of gases 0 drop of ammonia mixes with air 0 rate of diffusion is the rate of the mixing of gases 0 effusion is the term used to describe the passage of a gas through a tiny orifice into an evacuated chamber the rate of ef lsion measures the speed at which the gas is transferred into the chamber 0 see Figure 522 Effusion 0 Thomas Graham 18051869 a Scottish Chemist found experimentally that the rate of ef lsion of a gas is inversely proportional to the square root of the mass of its particles 0 see equation in text known as Graham s law of effusion Diffusion 0 because so many collision occur when gases mix diffusion is quite complicated to describe theoretically 58 Real Gases 0 an ideal gas is a hypothetical concept 0 no gas exactly follows the ideal gas law although many gases come very close at low pressure and or high temperatures 0 see Figure 525 0 see Figure 526 RFGCSU PageS of 6 Ch 05 Zumdahl 7th edwpd
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'