Chapter 14
What reflect the relationship between the spontaneity of a reaction and the sign of delta H?
1. A negative value of delta H favors spontaneity 2. The sign of delta H alone is not sufficient evidence to determine he spontaneity of a process
Why is the equation S = k ln W so rarely used to calculate the change in entropy of a system? How is delta S determined?
1. Tabulated standard entropy values are used to calculate entropy changes instead 2. It is difficult to determine the number of different possible arrangements (W).
What happens during the increase in entropy that occurs when substance changes from solid to liquid, or liquid to gas?
1. The number of possible arrangements of the particles increases 2. the energy of the particles increases during these phase changes
Name three forms of motional energy
1. Translational 2. Vibrational 3. Rotational
Which of the following changes are favored in a spontaneous process?
An overall decrease in energy and an increase in entropy
A tire is punctured, releasing the trapped gas inside, an ice cube melts at 273 K, and a crystal of sodium chloride is heated from 275 K to 290 K. These all would result in a _____ in entropy.
Increase
Two unknown reactions (A and B) are analyzed. It is found that reaction A is exothermic, while reaction B is endothermic. Which of these reactions is spontaneous?
Spontaneity cannot be determined from the given information.
Why does a reaction that results in an overall increase in the number of has molecules have a positive sign for delta Srxn?
The entropy of a substance in a gas phase is much higher that its entropy in the liquid or solid phase.
An atom of hydrogen is born to a metal surface (but free to move across it) with 10 possible sites of attachment. What would be the effect of increasing the size of the metal surface to 20 possible sites?
The entropy would increase, but it would be less than double the original entropy.
What much be known in order to assess the spontaneity of a chemical reaction or physical process at a particular set of conditions?
change in entropy and enthalpy
In order to assess the spontaneity of a chemical reaction or physical process both the change in ____ and ____ associated with the reaction or process must be known.
enthalpy and entropy
The ___ entropy of a substance is its absolute entropy at 1 atm.
standard