Laws of thermodynamics, enthalpy, entropy, Gibbs and Helmholtz energy, chemical potential and phase equilibria.
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- What does the first law of thermodynamics state?
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Energy cannot be created or destroyed, only converted between forms. The total energy of an isolated system is constant.- Define internal energy (U).
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The sum of all kinetic and potential energy of the particles in a system.- What is the relationship between delta-U, q, and w?
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Delta-U = q + w, where q is heat absorbed and w is work done on the system.- Define enthalpy (H).
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H = U + PV, the sum of internal energy and the product of pressure and volume.- When does delta-H equal q?
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At constant pressure: delta-H = q(p).- What does the second law of thermodynamics state?
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The entropy of an isolated system always increases for a spontaneous process.- Define entropy (S).
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A measure of the number of accessible microstates in a system; a measure of disorder.- For a spontaneous process at constant T and P, what is the condition involving entropy?
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Delta-S(universe) > 0, or equivalently, delta-S(system) + delta-S(surroundings) > 0.- What does the third law of thermodynamics state?
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The entropy of a perfect crystal at absolute zero (0 K) is zero.- What is the zeroth law of thermodynamics?
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If two systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other.- Define Gibbs free energy (G).
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G = H - TS, the energy available to do non-expansion work at constant T and P.- What is the condition for spontaneity in terms of delta-G?
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A process is spontaneous at constant T and P if delta-G < 0.- At equilibrium, what is the value of delta-G?
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Delta-G = 0.- Define Helmholtz free energy (A).
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A = U - TS, the energy available to do non-expansion work at constant T and V.- What is the relationship between Gibbs and Helmholtz free energies?
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G = A + PV, or delta-G = delta-A + P*delta-V.
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