CHAPTER 5 AP CHEMISTRY

PRESSURE BBBBarometer –M–M–M–Measure the atmospheric pressure  A A A Atmospheric pressure –M–M–M–Mass of the air being pulled toward the center of the earth by gravity –M–M–M–Manometer - on the board –1–1–1–1 standard atm. = 760 mmHg = 760 torr = kPa GGGGas laws –B–Boyles law –P–P 1 V 1 = P 2 V 2 AAAA gas that obeys the gas laws (look law up in book) is an Ideal Gas –C–Charles's law –V–V 1 = V 2 T 1 T 2 AAAA gas cannot have a negative volume. Therefore, temperature can never be below 0K. 0K will never be reached. Closest is K

CONTINUED AAAAvogardro’s law –V–V–V–Volume is directly proportional to the number of moles –V–V–V–V1 = V2 n1 n2  I I I Ideal gas law –P–P–P–PV = nRT –R–R–R–R = L.atm/ K.mol  C C C Combined gas law – P– P– P– P1V1 = P2V2 T1 T2

MOLAR MASS OF GAS MMMMolar mass (MM) = dRT P –d–d–d–d = density PPPPartial pressure TTTTotal pressure exerted is the sum of ALL gas pressures PPPPtotal = P1 + P = ntotal(RT/V)

MOLE FRACTION RRRRatio of the number of moles to the total number of moles XXXX1 = n1/ntotal = P1/Ptotal IIIIf a gas is collected by displacing water then the gas obtained would be a mixture of the gas and water vapor. The water vapor pressure would need to be removed before you could use the gases pressure. FFFFind the water vapor pressure at the temperature given and subtract it from the total pressure

KINETIC THEORY OF GASES TTTThe volume of individual particles are assumed zero  P P P Particles are in constant motion  P P P Particles exert no force on each other  A A A Average kinetic energy is directly proportional to its Kelvin temperature  R R R Real Gases have finite volumes and do exert forces on each other  ( ( ( (KE)average = 3/2 RT  K K K Kelvin temperature is an index of the random motions of the particles of gases  R R R Root mean square velocity (special kind of average)  U U U Urms = (3RT/M)1/2  U U U U = m/s, R = J/K.mol, J = kg.m2/s2, M = kg/mol

EFFUSION AND DIFFUSION REAL GASES EEEEffusion –P–P–P–Passage of a gas through a tiny orifice into a evacuated chamber –R–R–R–Rate of effusion for gas 1 = UrmsX1 = (M2)1/2 Rate of effusion for gas 2 Urms X2 (M1)1/2 –M–M–M–Molar mass (g/mol) is M in this formula  D D D Diffusion –M–M–M–Mixing of gases  R R R Real gases – I– I– I– Ideal gas behavior only occurs for real gases under the following conditions –L–L–L–Low pressure and/or high temperature

CONTINUED  V V V Van der Waal equation –[–[–[–[Pobs + a(n/V)2] x (V - nb) = nRT –P–P–P–Pobs = observed pressure, a(n/V)2 = pressure correction, (V - nb) = corrected volume –A–A–A–A and b are varied until the best fit of the observed pressure is obtained. These are found on table 5.3  R R R Read 5.10 UNDERSTAND THIS SECTION