PART- Chemical Thermodynamics and Thermochemistry Reference: Chapter 6 in textbook
1 PART 9 – Chemical Thermodynamics and Thermochemistry Reference: Chapter 6 in textbook
Basic Concepts System, Surroundings and Universe System Surrounding Universe Open System Both mass and energy exchange exist between the System and the Surroundings Close System Only energy(not mass)exchange exists between the System and the Surroundings Isolated System Neither energy nor mass exchange exists between the System and the Surroundings
Basic Concepts System, Surroundings and Universe System + Surrounding = Universe Open System Both mass and energy exchange exist between the System and the Surroundings. Close System Only energy (not mass) exchange exists between the System and the Surroundings. Isolated System Neither energy nor mass exchange exists between the System and the Surroundings. 2
State and state Function o State State: ensemble of all physical and chemical properties of a system ■ Example I mol H2 1 mol H 0°C.1atm 00C.0.5atm 22.4dm3 44.8dm State 1 State 2 3
State and State Function State State: ensemble of all physical and chemical properties of a system Example: 3 1 mol H2 1 mol H2 0 ºC , 1 atm 0 ºC , 0.5 atm 22.4 dm3 44.8 dm3 State 1 State 2
State and state Function State Function (State Quantity, State Variable) A property of a system that depends only on the current state of the system, not on the way how the system acquired that state, (i.e. independent of path) Only depends on the initial state and the final state H2O(s,25°C,1atm) H2O(g,25°C,1atm) H2O(,25°C,1atm)
State and State Function State Function (State Quantity, State Variable) A property of a system that depends only on the current state of the system, not on the way how the system acquired that state, (i.e. independent of path). Only depends on the initial state and the final state. 4 H2O (s, 25 ºC, 1atm ) H2O (g, 25 ºC, 1atm ) H2O (l, 25 ºC, 1atm )
Energy Internal Energy(U) The sum of all types of energy of a system: e.g Chemical bond, van der Waals interaction Movement of molecules molecular vibration We cannot know the absolute value of u but we can measure the change of U, (i.e. AU) Q: If the system takes two different paths to change from State 1 to State 2, which path has larger AU?
Energy Internal Energy (U) The sum of all types of energy of a system: e.g. Chemical bond, van der Waal’s interaction, Movement of molecules, Molecular vibration, … We cannot know the absolute value of U, but we can measure the change of U, (i.e. ΔU). Q: If the system takes two different paths to change from State 1 to State 2, which path has larger ΔU? 5