School of Chemical & Biological Engineering, Konkuk University

Size: px

Start display at page:

Download "School of Chemical & Biological Engineering, Konkuk University"

Berenice Watson
5 years ago
Views:

1 School of Chemical & Biological Engineering, Konkuk University

2 Chemistry is the science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions. Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-2

3 Physical chemistry is the application of physics to macroscopic, microscopic, atomic, subatomic, and particulate phenomena in chemical systems within the field of chemistry traditionally using the principles, practices and concepts of thermodynamics, quantum chemistry, statistical mechanics and kinetics. Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-3

4 Part I. Equilibrium Thermodynamics 1. The properties of gases 2. The first law 3. The second law 4. Physical transformations of pure substances 5. Simple mixture 6. Phase diagrams 7. Chemical equilibrium Phys. Chem. I Part II. Structure Part III. Change Selected chapters Phys. Chem. II Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-4

5 Learning is the acquisition and development of memories and behaviors, including skills, knowledge, understanding, values, and wisdom. It is the product of experience and the goal of education. Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-5

6 Knowledge on thermodynamic laws Skills to solve thermodynamic problems Ability to apply thermodynamic laws to natural phenomena How and why are the thermodynamic concepts created? What was the way they think to reach the thermodynamic laws? Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-6

7 First of all, you should learn the thinking ways of the genii to reach their conclusions. The thinking ways are often limited by his or her knowledge on the given subject. Therefore you should understand various knowledge, not memorize numerous knowledge. Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-7

8 Let s enjoy thinking natural phenomena via thermodynamics!!! Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-8

9 Lecture 1 Gas Laws Perfect Gas Equation Mixture of Gases Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-9

http://en.wikipedia.org/wiki/steam_engine Prof.

10 Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-10

11 Thermodynamics was born in the 19 th century to describe the operation of steam engines and to set forth the limits of what they can accomplish. For the 1 st and 2 nd laws, no proof in the mathematical sense. 1 st law: the total quantity of energy is constant. 2 nd law: the total entropy increases. Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-11

12 The simplest state of matter is a gas. The perfect gas is an idealized version of a gas. How can the state of the perfect gas be described? the gas laws, the perfect gas equation Which properties of real gases are different from the perfect gas? What is the origin of the differences? How can the states of real gases be described? equation of state for real gases: van der Waals equation Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-12

13 Let s imagine a gas as a collection of molecules (or atoms) in continuous random motion. Their average speeds increase as the temperature is raised. A gas differs from a liquid. 1. Except during collisions, the molecules of a gas are widely separated from one another. 2. They move in paths that are largely unaffected by intermolecular forces. Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-13

14 Physical state of a sample of a substance is defined by its physical properties. Sample A Sample B physical properties of A = physical properties of B physical state of A = physical state of B Physical state of a pure gas is specified by its pressure (p), volume (V), number of moles (n) and temperature (T). Pure gas can be described by an equation of state, an equation that interrelates the four variables. p f ( T, V, n) General form nrt p V Perfect gas Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-14

15 Pressure (p) is defined as force (F) divided by the area (A) to which the force is applied. p = F/A The origin of the force exerted by a gas is the incessant battering of the molecules on the walls of its container. Units: 1 Pa (pascal, SI) = 1 N/m 2 = 1 kg m/s 2 1 bar = 10 5 Pa (standard pressure) 1 atm = Pa (exactly) Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-15

16 Torricelli a student of Galileo Mechanical equilibrium Atmosphere Mercury in the column Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-16

17 Temperature (T) is the property that indicates the direction of a flow of energy as heat through a wall (boundary). Heat flows from high T to Low T. Diathermal: thermally conducting Adiabatic: thermally insulating. ex) vacuum flask Thermal equilibrium is established if no change of state occurs when two objects are in contact through a diathermal boundary. Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-17

Thermal expansion and contraction of liquids or gases are used to monitor the temperature.

18 If A is in thermal equilibrium with B, and B is in thermal equilibrium with C, then C is also in thermal equilibrium with A The zeroth law justifies the use of a thermometer for measuring the temperature. Thermal expansion and contraction of liquids or gases are used to monitor the temperature. Hg-in-glass thermometer The perfect-gas temperature scale is independent of the identity of the gas. thermodynamic temperature scale o T( K) ( C) Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-18

19 The equation of state of a gas at low pressure was established by combining a series of empirical laws. Isotherm Isobar Isochore Bolye s law pv = const. n and T Charles s law V = const. const. n and P p = const. const. n and V Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-19

20 The Boyle s and Charles s laws are the limiting law that is strictly true only in a certain limit (p 0). Avogadro s Principle Equal volumes of gases at the same temperature and pressure contain the same numbers of molecules. The Avogadro s principle is increasingly true as p 0. However, the principle is reasonably reliable at normal pressure (p ~ 1 bar). Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-20

21 The empirical observations can be combined into a single expression as below. pv = constant nt The constant of proportionality is found experimentally to be the same for all gases. That is called the gas constant (R). The perfect gas equation: pv nrt liter Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-21

22 pv nrt When the amount of perfect gas is fixed, the perfect gas equation can be plotted to a three-dimensional curve. The points forming the surface represent the only possible state of a perfect gas. Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-22

23 The isotherm, isobar and isochore correspond to the sections through the surface. Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-23

24 The perfect gas equation can be also used as an approximate equation to describe state of any real gas. However, it becomes increasingly exact as p 0. A gas that exactly obeys the equation of pv=nrt under all conditions is called a perfect gas or ideal gas. Standard ambient temperature and pressure (SATP): K and 1 bar Standard temperature and pressure (STP): 0 o C and 1 atm Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-24

25 Let s think a mixture of gases which consists of A, B, C, etc. The partial pressure (p J ) of a gas J in the mixture is defined as PJ xj P where x J is the mole fraction of the component and p is the total pressure of the mixture. nj xj n n B n A n When there is no J molecules in the mixture, x J = 0. When only J molecules are present in the mixture, x J = 1. Whatever the composition of the mixture, x A x B 1. Therefore, the sum of the partial pressures is equal to the total pressure. Dalton s law p A p B x A p x B p ( x x ) p Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch A B p

26 The pressure exerted by a mixture of gases (p) is the sum of the pressures (p J ) that each one would exert if it occupied the container alone. p p A p B Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-26

27 Physical Chemistry, Atkins, 8ed. Page 12 ~ 23 Prof. Yo-Sep Min Physical Chemistry I, Spring 2009 Ch. 1-27

Properties of Gases. Molecular interactions van der Waals equation Principle of corresponding states

Properties of Gases. Molecular interactions van der Waals equation Principle of corresponding states Properties of Gases Chapter 1 of Atkins and de Paula The Perfect Gas States of gases Gas laws Real Gases Molecular interactions van der Waals equation Principle of corresponding states Kinetic Model of