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 predictive theories applied to problems in chemistry. Using mathematics to solve questions in chemistry. More similar to physics than organic synthesis. 1
The problems answered by p- chem Because we are expecting mathematics to solve our chemistry question we will be asking rather simple questions. What is the pressure 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 But it is getting important questions like: better at this. H H C C KOH ClH 2 C C C CH 2 Cl H ? C H H CH Mathematics is not useful for solving every problem in chemistry In fact, it may not be useful for solving many problems in chemistry. Empirically determined: Theoretically calculated: solubility rules, reaction pH of a buffer solution, mechanisms, E2 vs. reaction rate, x - ray SN1., active site of an structure of a protein. enzyme. 2
How is P- Chem Structured? There are three main subdivisions: Thermodynamics Ch. 1 - 11 The macroscopic study of systems in equilibrium Kinetics Ch. 18 - 19 (in lab) The macroscopic study of systems approaching equilibrium Quantum mechanics Chem 314 Microscopic 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: Integration: 1 d(aV 2 ) dV V dV 2 -ax d e 2 a p dp dx Rules for exponents: Be able to use an integral table. There is a good one on our web page. lnV 1 lnV 0 = Textbook Appendix B. pg. 547 ChemActivity M1 pg. 329 3
Texts for the Course: Traditional textbook: It is very thorough and requires slow reading. Terrific figures and problems. Read sections 1.1 - 1.4. Look at math review in Appendix B. (B.2, B.4, B.6) Inquiry based workbook covering the topics of kinetics and thermodynamics. Work through ChemActivity M1 (pg 329 - 334) Look over activities G1 - G1B before lab. Things you already know (Highlights for starting thermodynamics) Intensive property: Does not depend on the amount of material. vs. Depends on the amount of Extensive property: material. mass The division of two extensive properties = density vol yields an intensive property. vol km Vm speed mole s Tables only list intensive properties. 4
Energy What is energy? This is difficult to answer. A property of the universe that is conserved. kg m 2 Units: = 1 joule 1 heart beat s 2 Forms of energy: gravitational columbic q 1 q 2 Kinetic ; T = 1/2 mv 2 Potential ; V = mgh V r Thermal energy ; U = 3/2 RT (for a monatomic ideal gas) Also: electrical, mechanical, electromagnetic Chapter 1 - Gases A system we can describe mathematically What properties must we measure to quantify a gas? Pressure, temperature, volume and # of moles Use molar volume, V m Pressure is a function of R T a molar volume and p(V m ,T ) = ? Vm b T Vm Vm b temperature. If volume and temperature are specified pressure is immediately known. This is an equation of state. 5
Pg. 6 Units for gases pascal Pressure = kg m 2 kg m force energy area = p = pressure s 2 m 2 s 2 m 3 volume How we measure pressure pressure volume = energy F m g A· h · · g p = = = A A A m = vol. density p = · g · h We measure the height a liquid is raised by a pressure. p = 645 mm Hg 10 5 Pa 750 mm Hg = 1 bar 1 Units for gases Volume: The size of the container. 1 liter (L) = 1 dm 3 = 1x10 -3 m 3 Temperature: What is temperature anyway? An indication of the direction in which heat will flow. More rigorous definitions to come. Unit: Kelvin (K) T K ( ) ( ° C ) 273.15 Zero th law of thermodynamics: Heat flows from a high temperature body to a low temperature body. 6
How the variables ( p,V m , & T) effect each other First observed by Const Temp. Robert Boyle (1662) Isotherm p constant p Vm 300 K V R T p Vm T Vm V L bar Ideal gas constant R = 0 . 08314 K mol What is the volume of CO 2 treated as and ideal gas at 500 K and 100 atm ? 0.08314 L bar 500 K Good to 1 R T K mol Vm p T ( ) = 0.41 L/mol significant Vm p 100 bar figure. Actual molar volume of CO 2 is 0.37 L/mol If the ideal gas law is a state equation then how is volume effected by temperature? Is the pressure greater or smaller for this state? R T p Vm T Slope = ? R /p Vm V m R T Vm p T ( ) = p Isobar: y = m· x + b constant p T Interesting intersection at V m = 0 This intersection is at - 273.15 ° C or 0 K 7
p Vm Units for the gas constant R T R p V m 1/T units m 3 1 kg m 2 kg J = 8.314 SI K m s 2 mol s 2 K mol K mol 1 L bar practical bar L 0 . 08314 K K mol 1 0.0821 L atm common atm L K K mol J 8.314 Useful conversion: R K mole = 101.3 J/ L atm R 0.0821 L atm K mole How change is expressed? A differential is used to express change. Const. Temp. dP p Partial differential Vm dV m T p Constant T R T p Differentiate the p Vm ideal gas equation Vm T V m R T dp = dV m Fixed volume 2 Vm Slope is always negative. p = Vm Pressure always decreases as volume increases. T 8
The derivative leads us back to calculus How would you write the derivative H d lim shown by the green tangent line? = H T ( ) T T 0 d T What is the derivative here? H(T) What is the derivative 1. here? Where is the Where is the derivative derivative largest? 2. negative? T The derivative reports the change in a function What does an integral of a function report? The area encompassed by that function. (The area under the curve.) V 1 V 2 P(V) What are the units of the shaded area? V 9
10
Recommend
More recommend
