tailieunhanh - Chapter 19: Chemical Thermodynamics

Spontaneous processes, entropy and the second law of thermodynamics, the molecular interpretation of entropy, gibbs free energy, free energy and the equilibrium constant,. is the main content of the lecture "Chapter 19: Chemical Thermodynamics". Invite you to consult the detailed content lectures to capture details. | Copyright 1999, PRENTICE HALL Chapter 19 Chemical Thermodynamics Chapter 19 David P. White University of North Carolina, Wilmington 1 1 1 1 Copyright 1999, PRENTICE HALL Chapter 19 Spontaneous Processes Thermodynamics is concerned with the question: can a reaction occur? First Law of Thermodynamics: energy is conserved. Any process that occurs without outside intervention is spontaneous. When two eggs are dropped they spontaneously break. The reverse reaction (two eggs leaping into your hand with their shells back intact) is not spontaneous. We can conclude that a spontaneous process has a direction. Copyright 1999, PRENTICE HALL Chapter 19 Spontaneous Processes A process that is spontaneous in one direction is not spontaneous in the opposite direction. The direction of a spontaneous process can depend on temperature: Ice turning to water is spontaneous at T > 0 C, Water turning to ice is spontaneous at T Spontaneous | Copyright 1999, PRENTICE HALL Chapter 19 Chemical Thermodynamics Chapter 19 David P. White University of North Carolina, Wilmington 1 1 1 1 Copyright 1999, PRENTICE HALL Chapter 19 Spontaneous Processes Thermodynamics is concerned with the question: can a reaction occur? First Law of Thermodynamics: energy is conserved. Any process that occurs without outside intervention is spontaneous. When two eggs are dropped they spontaneously break. The reverse reaction (two eggs leaping into your hand with their shells back intact) is not spontaneous. We can conclude that a spontaneous process has a direction. Copyright 1999, PRENTICE HALL Chapter 19 Spontaneous Processes A process that is spontaneous in one direction is not spontaneous in the opposite direction. The direction of a spontaneous process can depend on temperature: Ice turning to water is spontaneous at T > 0 C, Water turning to ice is spontaneous at T Spontaneous Processes Reversible and Irreversible Processes A reversible process is one that can go back and forth between states along the same path. When 1 mol of water is frozen at 1 atm at 0 C to form 1 mol of ice, q = Hvap of heat is removed. To reverse the process, q = Hvap must be added to the 1 mol of ice at 0 C and 1 atm to form 1 mol of water at 0 C. Therefore, converting between 1 mol of ice and 1 mol of water at 0 C is a reversible process. Allowing 1 mol of ice to warm is an irreversible process. To get the reverse process to occur, the water temperature must be lowered to 0 C. Copyright 1999, PRENTICE HALL Chapter 19 Spontaneous Processes Chemical systems in equilibrium are reversible. In any spontaneous process, the path between reactants and products is irreversible. Thermodynamics gives us the direction of a process. It cannot predict the speed at which the process will occur. Why are endothermic reactions spontaneous? Copyright 1999, PRENTICE HALL Chapter 19 Entropy and