What is Physical Chemistry?

Transcription

1 Chemistry 313 Dr. Caleb Arrington 10:30 am - 11:20 am M,W,&F Lab: Wednesday 2:00-5:00 Office RMSC 306-A What do we do the first day of every class? syllabus What is Physical Chemistry? Mathematically redictive theories alied to roblems in chemistry. Using mathematics to solve questions in chemistry. More similar to hysics than organic synthesis. 1

2 The roblems answered by -chem Because we are execting mathematics to solve our chemistry question we will be asking rather simle questions. What is the ressure of 1 mol CO 2 at 295 K in a 5 L vessel? The first half of the course is largely about gases because they are easiest to model. Currently mathematics is not wonderful at answering imortant questions like: Cl 2 C C C C 2 Cl KO? C But it is getting better at this. C C C Mathematics is not useful for solving every roblem in chemistry In fact, it may not be useful for solving many roblems in chemistry. Emirically determined: solubility rules, reaction mechanisms, E2 vs. SN1., active site of an enzyme. Theoretically calculated: of a buffer solution, reaction rate, x-ray structure of a rotein. 2

3 ow is P-Chem Structured? There are three main subdivisions: Thermodynamics Ch The macroscoic study of systems in equilibrium Kinetics Ch (in lab) The macroscoic study of systems aroaching equilibrium Quantum mechanics Chem 314 Microscoic study of atoms and molecules Mathematics is critical to P-Chem What mathematics am I going to need to be able to use? Prerequisites for Chem. 313: Calculus I & II Differentiation: d(av 2 ) dv 2 -ax d e dx Rules for exonents: lnv 1 lnv 0 = Integration: 1 dv V a 2 d Be able to use an integral table. There is a good one on our web age. Textbook Aendix B. g. 547 ChemActivity M1 g

4 Texts for the Course: Traditional textbook: It is very thorough and requires slow reading. Terrific figures and roblems. Read sections Look at math review in Aendix B. (B.2, B.4, B.6) Inquiry based workbook covering the toics of kinetics and thermodynamics. Work through ChemActivity M1 (g ) Look over activities G1 - G1B before lab. Things you already know (ighlights for starting thermodynamics) Intensive roerty: vs. Extensive roerty: Does not deend on the amount of material. Deends on the amount of material. mass The division of two extensive roerties = density yields an intensive roerty. vol km vol seed s mole Tables only list intensive roerties. 4

5 What is energy? Energy This is difficult to answer. A roerty of the universe that is conserved. Units: kg m 2 s 2 = 1 joule 1 heart beat Forms of energy: gravitational columbic q Kinetic; T = 1/2 mv 2 Potential; V = mgh 1 q 2 V r Thermal energy; U = 3/2 RT (for a monatomic ideal gas) Also: electrical, mechanical, electromagnetic Chater 1 - Gases A system we can describe mathematically What roerties must we measure to quantify a gas? Pressure, temerature, volume and # of moles Pressure is a function of molar volume and temerature. (,T) =? R T Use molar volume, If volume and temerature are secified ressure is immediately known. This is an equation of state. b a T b 5

6 Pressure force area = ow we measure ressure Units for gases kg m s 2 m 2 ascal kg m2 = s 2 m 3 ressure energy volume = ressure volume = energy Pg. 6 = F A = m g A = A h g A = 645 mm g m = vol. density = g h We measure the height a liquid is raised by a ressure. 750 mm g = 1 bar Pa Units for gases Volume: The size of the container. 1 liter (L) = 1 dm 3 = 1x10-3 m 3 Temerature: What is temerature anyway? An indication of the direction in which heat will flow. More rigorous definitions to come. Unit: Kelvin (K) T ( K ) ( C ) Zero th law of thermodynamics: eat flows from a high temerature body to a low temerature body. 6

7 ow the variables (,, & T) effect each other First observed by Robert Boyle (1662) Const Tem. 300 K constant V Isotherm R T T Ideal gas constant R = L K bar mol V What is the volume of CO 2 treated as and ideal gas at 500 K and 100 atm? ( T) R T L bar K mol 500 K V = 0.41 L/mol m 100 bar Actual molar volume of CO 2 is 0.37 L/mol Good to 1 significant figure. If the ideal gas law is a state equation then how is volume effected by temerature? T ( T) = R T R T y = m x + b Sloe =? R/ Is the ressure greater or smaller for this state? T Isobar: constant Interesting intersection at = 0 This intersection is at C or 0 K 7

8 Units for the gas constant R T units SI 1/T kg m s 2 ractical bar L m 3 mol common atm L Useful conversion: R R J K mole L atm K mole 1 K 1 K 1 K R kg m2 s 2 K mol L bar K mol L atm K mol = J/ L atm = J K mol A differential is used to exress change. dp d d = R T R T Constant T ow change is exressed? T Partial differential Differentiate the ideal gas equation 2 d T Fixed volume Const. Tem. = T Sloe is always negative. Pressure always decreases as volume increases. 8

9 The derivative leads us back to calculus ow would you write the derivative shown by the green tangent line? lim T 0 T d = ( T) d T What is the derivative here? (T) Where is the derivative negative? Where is the derivative largest? What is the derivative here? T The derivative reorts the change in a function What does an integral of a function reort? The area encomassed by that function. (The area under the curve.) V 1 V 2 P(V) What are the units of the shaded area? V 9

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