CY1001 BASIC CONCEPTS

Transcription

1 CY1001 BASIC CONCES Lecture 1. radeep Atomists and ionists 9/6/2010 1

2 1. Chemical thermodynamics 2. Statistical thermodynamics 3. Kinetics 4. Surface science Books: 1. G. W. Castellan, hysical Chemistry, 3 rd Edition, Narosa, New Delhi, W. Atkins, hysical Chemistry, 8 th Edition, Oxford University ress, Oxford, Silbey, Alberty, Bawendi, hysical Chemistry, 4th Ed. Lecture schedule utorials Evaluation

3 Quantum mechanics Statistical mechanics roperty hermodynamics ariation of heat with process ariable ime

4 UNIERSE SYSEM SURROUNDING OEN CLOSED ISOLAED Intensive and Extensive ariables ressure, olume, emperature, Heat, Mass 4

5 What is unique about hermodynamics? Independent of atomic and molecular theory. In chemical systems, thermodynamics helps to keep a record of energy flow. Equilibrium state of a chemical system can be understood from thermodynamics. It is a logical science, three statements describe thermodynamics; deductions from these laws constitute the equations. alidity of thermodynamic laws depends only on the basic laws and the logical deductions which follow from them. Since thermodynamics is itself a science, not dependent upon the foundations of other branches, it has an existence of its own.

6 A theory is the more impressive the greater the simplicity of its premises, the more different kinds of things it relates, and the more extended its area of applicability. Hence the deep impression that classical thermodynamics made upon me. It is the only physical theory of universal content concerning which I am convinced that, within the framework of the applicability of its basic concepts, it will never be overthrown. Albert Einstein

7 System Surroundings Characterization of a system Based on properties (1) intensive properties and (2) extensive properties ypes of systems (1) open, (2) closed, and (3) isolated systems. (1) homogeneous or (2) heterogeneous Chemical system hase, Component rocess, ath State function, ath function Exact and inexact differentials

8 Zeroth Law A B and B C, then A C { thermal equilibrium} First Law Law of conservation of energy

9 Work, heat Exothermic, endothermic First Law du dq dw Internal energy of an isolated system is constant ex d ex Work - ex d Free expansion 0 Isothermal work -(nr/) d - nr ln f / i (reversible) i f Indicator diagram James Watt

10 q and w are positive, when energy is transferred to the system q and w are negative, when energy is lost from the system Exact and Inexact differentials b a du U b U a U Exact differential 9/6/2010 b a w w( w b w a ) Inexact differential 10

11 9/6/ Sum of two inexact differentials can be an exact differential (first law) est for exactness-euler's theorem ), ( y x f z dy y z dx x z dz x y + if then, When y x x y y z x x z y hen z is an exact differential Inexact differentials can be converted to exact differentials by multiplying with integrating factors

12 he General Expression for Work From hysics, Work, w Fd cos θ When θ 180 0, Work, w -Fd w dw -F.dz F But, F ressure x Area.A herefore, dw -.A.dz Now, A.dz d dw -.d w 2 d 1 9/6/

13 Concept of reversibility 1, 1, m 2 SINGLE SE COMRESSION mg 2 A h m 1 w mgh ( 1) 2 2 1, 1 2, wo, three and infinite number of steps Same compression can be Done with less work! w w 2 1 d 9/6/

14 Different situations F w Free expansion Expansion against constant pressure If is constant, w - ( 2 1 ) Isothermal reversible expansion 9/6/2010 w nr 2 1 d w nr ln

15 9/6/ d U d U du + HEA CAACIY U as a function of and d U d U q ext + + d q du ext Since, At constant volume, d U q C U d q Heat capacity at constant volume C d q ath dependant (constant or )

16 HEA CAACIY C U U 2 1 C d If C is constant over a small range of temperature, U C We have seen that, du U d + U d gas vacuum Since d 0, du U d U 0 0 Since Joule Found that q 0; and Internal ressure w 0 9/6/2010 his is not correct for real gases. 16

17 Change of state at constant pressure Enthalpy U U U q qp ( ( U + ) ( U ) q ) q H 2 H 1 H U + q dh 9/6/

18 H as a function of and dh H d + H d Since q dh and at constant, q H d q d H C Heat capacity at constant pressure If C is independent of temperature, H C 9/6/

19 9/6/ C - C nr d U d U q ext + + divide by d and setting C d dq U C C + For an ideal gas, and nr 0 U nr C C

20 Enthalpy, H U + Calorimetry Isotherm and adiabat hermochemistry Heat of formation, Δ f H o Hess s Law Adiabat α1/ γ Isotherm Ad α1/ Born-Haber Cycle Kirchhoff s equation Δ r H o ( 2 ) Δ r H o ( 1 ) + ʃ Δ r C p o Equipartition principle d Joule experiment Π (U/ ) Joule-homson Experiment μ (/ ) H

21 It is all about heat. Galileo Galilei hermodynamics, History

22 Francis Bacon Joseph Black,

23 James rescott Joule

24 James Watt

25 Sadi Carnot

26 Rudolf Clausius

27 Lord Kelvin (William homson)

28 Ludwig Boltzmann

29 Josiah Willard Gibbs

30 Jacobus Henricus van 't Hoff

31 Walther Hermann Nernst

32 Gilbert Newton Lewis