Dr. S. M. Condren Chapter 5 The Gaseous State

Dr. S. M. Condren Properties of Gases can be compressed exert pressure on whatever surrounds them expand into whatever volume is available easily diffuse into one another can be described in terms of their temperatures and pressure,the volume occupied, and the amount (number of molecules or moles) present

Dr. S. M. Condren Mercury Barometer

Dr. S. M. Condren Composition of Air at Sea Level

Dr. S. M. Condren Important Units of Pressure Conversion factor to learn

Dr. S. M. Condren Boyle’s Law At constant temperature and mass of gas: V  1/P V = a * 1/P where a is a proportionality constant thus VP = a V 1 P 1 = a = V 2 P 2 V 1 P 1 = V 2 P 2

Dr. S. M. Condren Boyle’s Law

Dr. S. M. Condren Boyle’s Law

Dr. S. M. Condren Effect of Pressure Differential

Dr. S. M. Condren Charles’ Law At constant pressure and mass of gas: V  T V = b * T where b is a proportionality constant V/T = b V 1 /T 1 = b = V 2 /T 2 V 1 /T 1 = V 2 /T 2

Dr. S. M. Condren Charles’ Law

Dr. S. M. Condren Combined Gas Law At constant mass of gas V  T/P V = d * (T/P) where d is a proportionality constant (VP)/T = d V 1 P 1 = d = V 2 P 2 T 1 T 2 V 1 P 1 = V 2 P 2 T 1 T 2

Dr. S. M. Condren Avogadro’s Law At constant pressure and temperature V  n V = c * n where c is a proportionality constant V/n = c V 1 /n 1 = c = V 2 /n 2 V 1 /n 1 = V 2 /n 2

Dr. S. M. Condren Ideal Gas Law V  (n * T)/P V = R * (n * T)/P where R is proportionality constant P * V = n * R * T (P*V)/(n*T) =R Thus, (P 1 *V 1 )/(n 1 *T 1 ) = (P 2 *V 2 )/(n 2 *T 2 )

Dr. S. M. Condren What will be volume of an ideal gas at absolute zero? - 10 mL/mole 0 mL/mole 10 mL/mole

Dr. S. M. Condren Ideal Gas Constant R = L*atm/mol*K R has other values for other sets of units. R = mL*atm/mol*K = J/mol*K = cal/mol*K

Dr. S. M. Condren Molar Mass from Gas Density gas density = #g/V = d PV = nRT where n = #g/MM PV = (#g/MM)*RT MM = (#g*R*T)/(P*V) MM = (#g/V)*((R*T)/P) = (d*R*T)/P

Dr. S. M. Condren Dalton’s Law of Partial Pressures The total pressure of a mixture of gases is equal to the sum of the pressures of the individual gases (partial pressures). P T = P 1 + P 2 + P 3 + P whereP T => total pressure P 1 => partial pressure of gas 1 P 2 => partial pressure of gas 2 P 3 => partial pressure of gas 3 P 4 => partial pressure of gas 4

Dr. S. M. Condren Dalton’s Law of Partial Pressure

Dr. S. M. Condren Collecting Gases over Water

Dr. S. M. Condren Example: What volume will 25.0 g O 2 occupy at 20 o C and a pressure of atm? (25.0 g)(1 mol) n = = mol (32.0 g) V =?; P = atm; T = ( )K = 293K R = L*atm/mol*K V = nRT/P = (0.781 mol)( L*atm/mol*K)(293K) 0.880atm = 21.3 L

Dr. S. M. Condren Example A student generates oxygen gas and collects it over water. If the volume of the gas is 245 mL and the barometric pressure is 758 torr at 25 o C, what is the volume of the “dry” oxygen gas at STP? P water = 23.8 torr at 25 o C; P O2 = P bar - P water = ( ) torr = 734 torr P 1 = P O2 = 734 torr; P 2 = SP = 760. torr V 1 = 245mL; T 1 = 298K; T 2 = 273K; V 2 = ? (V 1 P 1 /T 1 ) = (V 2 P 2 /T 2 ) V 2 = (V 1 P 1 T 2 )/(T 1 P 2 ) = (245mL)(734torr)(273K) (298K)(760.torr) = 217mL

Dr. S. M. Condren Kinetic Molecular Theory Matter consists of particles (atoms or molecules) in continuous, random motion.

Dr. S. M. Condren Kinetic Molecular Theory: Gases particles in continuous, random, rapid motion collisions between particles are elastic volume occupied by the particles is negligibly small effect on their behavior attractive forces between particles have a negligible effect on their behavior gases have no fixed volume or shape, take the volume and shape of the container

Dr. S. M. Condren Maxwell’s Distribution of Speeds

Dr. S. M. Condren Real Gases have a finite volume at absolute zero have attractive forces between gas particles

Dr. S. M. Condren Van der Waals Equation (P + a/V 2 )(V - b) = nRT wherea => attractive forces b => residual volume

Dr. S. M. Condren

Carbon Dioxide and Greenhouse Effect

Dr. S. M. Condren Some Oxides of Nitrogen N 2 O NO NO 2 N 2 O 4 2 NO 2 = N 2 O 4 brown colorless NO x

Dr. S. M. Condren Air Pollution in Los Angles