In the name of Allah

Transcription

1 In the name of Allah

2 Physical chemistry- 2 nd state semester 1 Petroleum and petrochemical engineering. Lecture No. 1 General Introduction In Physical Chemistry Assistance prof. Dr. Luma Majeed Ahmed lumamajeed2013@gmail.com, luma.ahmed@uokerbala.edu.iq

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4 Physical Chemistry: It is the application of the physical methods to chemical problems to include the qualitative and quantitative study. Standard Temperature and Pressure (STP) Standard temperature and pressure is given the symbol STP. It is a reference point for some gas calculations. Standard P atm or kpa Standard T K or 0.00 o C

5 5 C 9 F 32 K = ºC Gas laws must use the Kelvin scale to be correct.

6 At the macroscopic level, a complete physical description of a sample of a gas requires four quantities: 1. Temperature (expressed in K) 2. Volume (expressed in liters) 3. Amount (expressed in moles) 4. Pressure (given in atmospheres) These variables are not independent if the values of any three of these quantities are known, the fourth can be calculated. Ideal Gas Behavior The gas may be considered to be ideal at low pressures and relatively high temperatures, conditions under which the free space within the gas is large and the attractive forces between molecules are small.

7 1. Boyle s Law ( ) The pressure of a fixed amount of gas varies inversely with the volume if the temperature is maintained constant. PV=constant at constant T and n (isothermic process) Low T High T Robert Boyle ( ). Son of Earl of Cork, Ireland.

8 2. Charles s Law ( ) or Gay-Lussac s Law ( ) The volume of a definite quantity of gas at constant pressure is directly proportional to the absolute temp. V α T at constant P and n (T: absolute Kelvin temperature scale) (Isobaric process) Jacques Charles ( ). Isolated boron and studied gases. Balloonist.

9 3.Avogadro's Hypothesis : The amount of substance n (mole) is proportional to the volume at a fixed T and P. V ɑ n (at constant T and P) Approximate molar volumes of gas 24.0 L at 298K 22.4 L at 273K Avogadro

10 UNIVERSAL GAS CONSTANT (R) Combining all 3 laws V (1/p)(T)(n) V nt/p Rearranging, pv = (constant)nt Thus we get the ideal gas equation: Volume Universal Gas Constant Pressure P V = n R T No. of moles Temperature

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12 Universal Gas Constant Universal gas constant is given on R = J /mol K = bar m 3 /mol K = L atm/mol K = cal /mol K = ft-lbf/lbmol-r = psia-ft 3 /lbmol-r

13 Common Units of Pressure Unit Average Air Pressure at Sea Level pascal (Pa), 1Pa 1 101,325 kilopascal (kpa) atmosphere (atm) millimeters of mercury (mmhg) 1 (exactly) 760 (exactly) inches of mercury (inhg) torr (torr) pounds per square inch (psi, lbs./in 2 ) N m (exactly)

14 4. Dalton s Law of Partial Pressure The total pressure of a mixture of gases is equal to the sum of the partial pressures of the individual components of the mixture. P total = P 1 + P 2 + P partial pressure John Dalton Graham's Law of Diffusion (Effusion) At constant temperature and pressure the rates of diffusion of various gases vary inversely as the square roots of their densities or molecular weights. Thomas Graham u u 1 M 2 2 M u 1 u 2 = t 2 t 1

15 Diffusion Is the gas transfers from high concentration to low concentration, and this process leads to slowly mixing of gas. Effusion Is the process that occurs when the gas escapes through a small hole

16 Kinetic Molecular Theory of Gases

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