Chemistry 116 1st Edition Exam # 7 Study GuideTuesday April 28thThe Gaseous State Gas Pressure and its MeasurementGases – fluid state of matter with no definite shape or volume - Can be compressed into smaller and smaller volumes- Are accurately described with simple laws involving only four variables: P, T, V, and no P=pressureo T=temperatureo V=volumeo N=molesPressure – force exerted per unit area- Atmospheric pressure – a column of air mass that weighs down on the earth’s surface- Gases exert a force against the walls of its container- Pressure units- P=force/areaImportant Units of Pressure! (Know the * units)*Pascal (Pa) – kg/(ms˄2)Atmosphere (atm) – 1atm = 1.01325 x 10˄5 Pa = 101 kPa*mmHg, or torr – 760 torr = 1 atmBar – 1.01325 bar = 1 atmBarometer – measures atmospheric pressureManometer – measures gas pressure Empirical Gas Laws – simple relationships among different gas variablesEmpirical = from experiment Name Constant(s) Relationship EquationBoyle’s Law n, T P – 1/V P1V1 = P2V2Charles’s Law n, P V – T V1/T1 = V2/T2Gay-Lussac’s Lawn, V P – T P1/T1 = P2/T2Combined Gas Lawn PV – T P1V1/T1 = P2V2/T2Avogadro’s LawP, T V – n V1/n1 = V2/n2Boyle’s Law (Butt Tattoo – in Boyle’s Law, Temp is fixed)- Compressibility – gases can be squeezed into smaller and smaller volumes (pressureincreases)- Real gases eventually condense to liquid (if pressure is high enough and temp is lowenough)Know that 1dm˄3 = 1LCharles’s Law (City Police – in Charles’s Law, Pressure is fixed)- Always convert temperatures to Kelvino Tk = Tc + 273.15Gay-Lussac’s Law (Grape Vine – in Gay-Lussac’s Law, Volume is fixed)Thursday April 30thSymbolic Gas Law Problems (Combined Gas Law Problem)- Gas at P, V, T, where P = 1atm- Temperature is reduced to half its value- Volume is increased by 3 times- What is the new pressure?P1V1/T1 = P2V2/T2P1 = 1atm P2 = ?V1 = V V2 = 3VT1 = T T2 = T/2So, insert the following into the equation and solve to get P2 = 1/6 x P1Law of Combining Volumes – at a fixed T and P, volumes of gaseous reactants combine in ratios of small whole numberAvogadro’s Law - at a fixed T and P, equal volumes of any two gases contain the same number ofmolecules V1/n1 = V2/n2Molar Volume and STP- Molar Volume – volume of one mole of gas - Depends on T and P (but not gas type)- Standard temp and pressure (STP) – 0 degrees C and 1 atm- Molar volume at STP is 22.41 LKnow STP!The Gaseous StateIdeal Gas Law – all gases obey the ideal gas law at low pressure and high temperaturePV = nRT(atm)(L) = (mol)(R)(K)R = (L)(atm)/(K)(mol)Where R is the molar gas constant (this number will be given to you on the exam)R = 0.0821 Latm/molK- T is always in kelvin- R is a proportionality factor- PV has units of energy- 1 L atm = 101.325 JTo use Empirical Gas Laws: some variable is changing, some are fixedTo use Ideal Gas Laws: nothing is changing, everything is fixedTuesday May 5thStoichiometry Problems Involving Gas Volumes- Use ideal gas lawGas Mixtures: Law of Partial PressuresDalton’s Law of Partial Pressures – the total pressure of a mixture of gases is the sum of the partial pressures for all the different components- Ideal gases do not interact with or distinguish one anothero Ideal gas law: Ptotal x V=ntotalRTo Add the moles of all gas componentso N total = n1 (number of moles of component 1) + n2 (number of moles of component 2) o Ptotal = P1 + P2- Partial Pressureo PiV = niRT- Mole Fractiono Xi = ni/ntotal = Pi/Ptotalo Pi = xi