Physical chemistr Physical Chemistry Cheng Xuan February 2004, Spring Semester
1 Physical Chemistry Cheng Xuan February 2004, Spring Semester Physical Chemistry
Physical Chemistry Summary Ideal gases/Perfect gases Key Notes e Gases: a fluid which has no intrinsic shape and which e expands indefinitely to fill any container in which it is held The ideal gas equations: the relations among the amount of gas substance, temperature, pressure and volume PV=nRT PYm=RT Vm: molar gas volume
3 Key Notes Ideal Gases/Perfect Gases Physical Chemistry Summary Gases: a fluid which has no intrinsic shape, and which expands indefinitely to fill any container in which it is held. The ideal gas equations: the relations among the amount of gas substance, temperature, pressure and volume. PV = nRT PVm = RT Vm: molar gas volume
Physical Chemistry Summary Ideal gases/Perfect gases Key Notes e Partial pressure: the pressure exerted by each component In a gaseous mixture P=nrt/v n. mole irp total x;: mole fraction e Dalton's law: the total pressure exerted by a mixture of ideal gases in a volume is equal to the arithmetric sum of the partial pressures total niota rT/y
4 Key Notes Ideal Gases/Perfect Gases Physical Chemistry Summary Dalton’s law: the total pressure exerted by a mixture of ideal gases in a volume is equal to the arithmetric sum of the partial pressures. Ptotal = ntotalRT/V Partial pressure: the pressure exerted by each component in a gaseous mixture. Px = nxRT/V Pi = xiPtotal nx : mole xi : mole fraction
Physical Chemistry Chapter 2 CHAPTER 2 -. The First Law of Thermodynamics Basic Concepts Isothermal A system which is held at constant temperature Adiabatic: A system in which energy may be transferred as work but not as heat Diathermic: a system which allows energy to escape as heat through its boundary if there is a difference in temperature between the system and its surroundings
5 Isothermal: A system which is held at constant temperature Adiabatic: A system in which energy may be transferred as work, but not as heat. CHAPTER 2 The First Law of Thermodynamics Basic Concepts Diathermic: A system which allows energy to escape as heat through its boundary if there is a difference in temperature between the system and its surroundings. Physical Chemistry Chapter 2
Physical Chemistry Chapter 2 Interna l Energy Internal energy: Total amount of energy in a system. The sum total of all kinetic and potential energy within the system Internal energy changes: The sign of AU Negative values: a system loses energy to the surroundings Positive values: a system gains energy from the surroundings
6 Internal energy: Total amount of energy in a system. The sum total of all kinetic and potential energy within the system. Internal energy changes: The sign of U Negative values: a system loses energy to the surroundings Positive values: a system gains energy from the surroundings Physical Chemistry Chapter 2 Internal Energy
Physical Chemistry Chapter 2 Thermodynamic Properties of system Extensive property: The value of the property changes according to the amount of material which is l present( e. g, mass, volume, internal energy) e Intensive property: independent of the amount of material which is present(e.g temperature, density) State functions: the value of a particular property for a system depends solely on the state of the system at time(e.g, pressure, volume, internal energy, entropy Path functions: A property depends upon the path by e which a system in one state is changed into another state(e.g, work, heat
7 Extensive property : The value of the property changes according to the amount of material which is present (e.g., mass, volume, internal energy) Intensive property:independent of the amount of material which is present (e.g., temperature, density) Thermodynamic Properties of system State functions: the value of a particular property for a system depends solely on the state of the system at time (e.g., pressure, volume, internal energy, entropy) Path functions: A property depends upon the path by which a system in one state is changed into another state (e.g., work, heat) Physical Chemistry Chapter 2
Physical Chemistry Chapter 2 Work Work: the transfer of energy as orderly motion due to energy being expanded against an opposing force(in mechanical terms) dw= F dx (210)* Reversible p-v work dwrey =-Pdv closed system, reversible process (2.30)* rey Pdv closed system, reversible process(2.31)
8 Work: the transfer of energy as orderly motion due to energy being expanded against an opposing force (in mechanical terms) Physical Chemistry Chapter 2 Work dw Fx dx (2.10)* Reversible P-V Work wrev PdV 2 1 = − closed system, reversible process (2.31) dw (2.30)* rev = -PdV closed system, reversible process
Physical Chemistry Chapter 2 Reversible p-v work dx -F=F=PA Piston moving- (a) Expansion(dv>0) F、=F=PA Piston moⅴing g (b) Compression(dv <0
9 Reversible P-V Work (a) Expansion (dV > 0) (b) Compression (dV < 0) V dx Piston moving Fx=F=PA V dx Piston moving Fx=F=PA Physical Chemistry Chapter 2
Physical Chemistry Chapter 2 Heat: the transfer of energy as disorderly motion as e the result of a temperature difference between the system and its surroundings exothermic: a process that releases energy as heat (all combustion reactions endothermic: processes that adsorb energy as heat (the vaporization of water an adiabatic system a)an an endothermic exothermic process process 10
10 exothermic: a process that releases energy as heat (all combustion reactions) endothermic: processes that adsorb energy as heat (the vaporization of water) Heat: the transfer of energy as disorderly motion as the result of a temperature difference between the system and its surroundings. (a) (b) Physical Chemistry Chapter 2 an adiabatic system (a) an endothermic process (b) an exothermic process
Physical Chemistry Chapter 2 Heat: the transfer of energy as disorderly motion as the result of a temperature difference between the system and its surroundings endothermic: energy enters as heat from the surroundings, the system remains at the same T(c) exothermic: energy leaves as heat from the system, the system remains at the same T(d) a diathermic container Heat An Heat ISothermal ocess (d)
11 Heat: the transfer of energy as disorderly motion as the result of a temperature difference between the system and its surroundings. Heat (c) Heat (d) a diathermic container Physical Chemistry Chapter 2 endothermic: energy enters as heat from the surroundings, the system remains at the same T (c) exothermic: energy leaves as heat from the system, the system remains at the same T (d) An isothermal process