Chapter 5 The Gaseous State HST Mr. Watson

HST Mr. Watson 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

HST Mr. Watson Mercury Barometer

HST Mr. Watson Composition of Air at Sea Level

HST Mr. Watson Important Units of Pressure Conversion factor to learn

HST Mr. Watson 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

HST Mr. Watson Boyle’s Law

HST Mr. Watson Boyle’s Law

HST Mr. Watson 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

HST Mr. Watson Charles’ Law

HST Mr. Watson 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

HST Mr. Watson 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

HST Mr. Watson 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 )

HST Mr. Watson What will be volume of an ideal gas at absolute zero? - 10 mL/mole 0 mL/mole 10 mL/mole

HST Mr. Watson 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

HST Mr. Watson 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

HST Mr. Watson 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

HST Mr. Watson Dalton’s Law of Partial Pressure

HST Mr. Watson Collecting Gases over Water

HST Mr. Watson 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

HST Mr. Watson 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

HST Mr. Watson 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

HST Mr. Watson Kinetic Molecular Theory Matter consists of particles (atoms or molecules) in continuous, random motion.

HST Mr. Watson Kinetic Molecular Theory: Gases particles in continuous, random, rapid motion collisions between particles are elastic volume occupied by the particles has a 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

HST Mr. Watson Maxwell’s Distribution of Speeds

HST Mr. Watson Real Gases have a finite volume at absolute zero have attractive forces between gas particles

HST Mr. Watson Van der Waals Equation (P + a/V 2 )(V - b) = nRT wherea => attractive forces b => residual volume

HST Mr. Watson

HST Mr. Watson

HST Mr. Watson Carbon Dioxide and Greenhouse Effect

HST Mr. Watson 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

HST Mr. Watson Air Pollution in Los Angles