Entropy; From Brightspace Flashcards
What are the two ways a new thermodynamic function will be derived?
i) From the analysis of an ideal engine (Carnot Cycle)
ii) From a statistical perspective analyzing the probability of distributing atoms
What is a common feature of spontaneous change in mechanical systems?
The loss of some form of energy
Who suggested that the direction of spontaneous changes in chemical systems is determined by the loss of energy?
Marcellin Bertholet
What type of changes did Bertholet propose are all exothermic?
All spontaneous chemical and physical changes
What is an example of a spontaneous process that is endothermic?
The melting of ice at room temperature
What are state functions?
Properties that define a state and do not depend on how we reach that state
What are the two types of paths that are key to understanding spontaneity?
- Reversible
- Irreversible
What is a reversible process?
One for which we can restore the system to its original condition with no change to the surroundings
What is an irreversible process?
One that leaves the surroundings changed when the system is restored to its original state
In the context of an ideal gas expanding at constant temperature, what is w for the expansion into a vacuum?
w = 0
What does the first law of thermodynamics state?
Energy is conserved
What is the mathematical expression for the first law of thermodynamics?
∆ E = q + w
What does the change in internal energy (∆ E) equal?
The heat absorbed (or released) plus the work done on (or by) the system
What is entropy, S, in relation to state functions?
A state function that characterizes the state of a system
What does the change in entropy (∆ S) depend on?
The initial and final states of the system
What is the equation for calculating the change in entropy (∆ S)?
∆ S = q rev / T
For isothermal processes, what is ∆ S equal to?
q rev divided by the absolute temperature
What is the enthalpy of fusion for H2O?
∆ H fusion = 6.01 kJ/mol
How do you calculate ∆ S fusion for melting 1 mol of ice at 273 K?
∆ S fusion = q rev / T
What is the entropy change of the universe (∆ S univ) in the example of ice melting in the palm of your hand?
Positive overall ∆ S univ = 2.6 J/K
What is the entropy change of the surroundings (∆ S surr) when ice melts in hand?
∆ S surr = -19.4 J/K
In the context of the first law of thermodynamics, what is the key idea?
Energy is conserved in any process
True or False: Entropy is conserved in a spontaneous process in the same way that energy is conserved.
False
