Chapter 19 - Thermodynamics Flashcards
The value of this term for an isothermal system is qrev/T
entropy
A statement that the overall entropy change during a spontaneous process is greater than zero.
second law of thermodynamics
For a system at equilibrium at constant pressure and temperature we find that the change in the value of this term is zero
Gibb’s free energy (G)
It proceeds on its own without external assistance and occurs in a definite direction.
spontaneous process
A term associated with a molecule moving in one direction.
translational motion
Atoms in a molecule moving internally with respect to one another
vibrational motion
Molecules moving around an internal axis
rotational motion
(T/F) According to the third law of thermodynamics, the entropy of any crystalline solid at absolute zero temperature is zero
False. Only for pure crystalline solids does S=0 at 0 K. The presence of impurities results in S>0.
(T/F) When heat is released in a chemical reaction in an isolated system (no exchange of energy between system and surroundings), the entropy of the surroundings increases.
False. An isolated system cannot exchange heat with its surroundings. Therefore no heat is transferred to the surrounding and entropy is not changed.
(T/F) The equilibrium constant for a system can be calculated if the Gibbs free energy change for the reaction is known
False. We need standard Gibbs free energy change.
(T/F) The standard free energy of formation of any pure substance at standard state conditions is zero.
False. It is zero only for elements in their standard states, not all substances.
(T/F) The standard molar entropy for N2(g) at 290 K is zero.
False. Only at absolute zero is the standard molar entropy for a perfect, pure crystalline substance equal to zero.
(T/F) A reaction that is spontaneous in the forward direction only is an irreversible reaction
True
(T/F) The pathway between reactants and products in a state of equilibrium is a reversible pathway.
True
