In: Chemistry
1. In each of A-C, below, indicate whether:
a) the statement is possible under the laws of thermodynamics; b) the statement violates the First Law; c) the statement violates the Second Law. In the case of a Second Law violation, circle the name of the scientist whose version of the second law is most simply and obviously broken. In each case there is a best name, but feel free to explain your choice. (Adapted from Bill Reinhardt.)
A. A novel and reversible heat engine absorbs 10 kJ of energy from a high temperature bath, performs 8 kJ of work on the surroundings, and exhausts 5 kJ of heat into a low temperature heat bath.
a. possible
b. violates First Law
c. violates Second Law: Kelvin Clausius Boltzmann
B. One night you wake up to discover that all the air in your room has gone under your bed. Note that this happens with no change in energy or temperature.
a. possible
b. violates First Law
c. violates Second Law: Kelvin Clausius Boltzmann
C. A novel & reversible heat engine absorbs 10 kJ of energy from a low temperature reservoir, performs 8 kJ of work on the surroundings, and exhausts 2 kJ of energy into a high temperature bath.
a. possible
b. violates First Law
c. violates Second Law: Kelvin Clausius Boltzmann
A) violates first law:
Explanation: The law of conservation of energy states that the total energy of an isolated system is constant; energy can be transformed from one form to another, but cannot be created or destroyed.
Here, the heat engine absorbs 10 kJ heat from a high temperature bath, performs 8 kJ of work on the surroundings. The rest of the heat i.e., 2 kJ heat should be delivered into the low temperature bath. The extra 3 kJ here come from nothing, it violates the first law which states that energy cannot be created.
B) violates Second Law: Boltzmann
Explanation: According to Boltzmann's statement, the entropy of an isolated system never decreases. Such a system spontaneously evolves towards thermodynamic equilibrium, the state with maximum entropy.
Here no change in energy or temperature occurs in the process. Decreases of temperature may decreases the entropy to some extent, but the case in the question is different. All of the air cannot contract spontaneously into a small volume, that would violate the second law of thermodynamics.
C) violates second law: Clausius
Explanation:
Clausius statement: No engine can transfer heat from a cold to a hot reservoir without input of work.
Here the engine performs work in the surrounding. It is an ordinary experience that heat cannot spontaneously flow from cold regions to hot regions without external work being performed on the system, for example, in a refrigerator, heat flows from cold to hot, but only when forced by an external agent, the refrigeration system.