Chapter 15 Flashcards
In an isothermal process, there is no change in ________
temperature
A gas is expanded to twice its original volume with no change in its temperature. This process is ________
isothermal
An ideal gas is compressed to one-half its original volume during an isothermal process. The final pressure of the gas ________
increases to twice its original value
A gas is quickly compressed in an isolated environment. During the event, the gas exchanged no heat with its surroundings. This process is ________
adiabatic
The process shown on the PV diagram is an ________
isobaric expansion
When water freezes, the entropy of the water ________
decreases
During an isothermal process, 5.0 J of heat is removed from an ideal gas. What is the change in internal energy of the gas?
zero
During an isothermal process, 5.0 J of heat is removed from an ideal gas. What is the work done by the gas in the process?
-5.0 J
An ideal gas undergoes an adiabatic process while doing 25 J of work. What is the change in internal energy?
-25 J
A heat engine receives 7000 J of heat and loses 3000 J in each cycle. What is the efficiency?
57%
A heat engine has an efficiency of 35.0% and receives 150 J of heat per cycle. How much work does it perform in each cycle?
52.5 J
What is the Carnot efficiency of an engine which operates between 450 K and 310 K?
31%
What is the maximum theoretical efficiency possible for an engine operating between 100°C and 400°C?
45%
What is the change in entropy when 50 grams of ice melt at 0°C?
60.9 J/K
What is the change in entropy when 100 g of water at 10°C is mixed with 100 g of water at 40°C?
1.0 J/K
What is the change in entropy when 1 kg of water at 0°C is mixed with 3 kg of water at 20°C?
7.7 J/K
1.0 kg of steam at 100°C condenses to water at 100°C. What is the change in entropy in the process?
-6.1 x 10^3 J/K
On a very hot day, could you cool your kitchen by leaving the refrigerator door open?
No, the refrigerator would exhaust more heat into the room than it takes out of the room.
In the closed thermodynamic cycle shown in the PV diagram, the total work done by the gas during a complete cycle is:
postive
clockwise closed cycle = positive total work
counter-clockwise closed cycle = negative total work
A heat engine exhausts 7800 J of heat while performing 2600 J of useful work. What is the efficiency of this engine?
Which of the following is the best example of a reversible process?
A block of metal surrounded by water at a slightly higher temperature slowly heats up.
- a reversible process is carried out slow enough that is could be considered a series of equilibrium states
A Carnot engine’s operating temperatures are 210°C and 45°C. The engine’s power output is 950 W. Calculate the rate of heat output.
an irreversible heat engine
*efficiency is smaller than the Carnot engine efficiency so it must be an irreversible heat engine
A restaurant refrigerator has a coefficient of performance of 5.0. If the temperature in the kitchen outside the refrigerator is 32°C, what is the lowest temperature that could be obtained inside the refrigerator if it were ideal?
* Coefficient of performance (COP)
What is the COP of a Carnot heat pump used to remove heat from ice at 0.0°C and add heat to a room at 20.0°C?
14.7
293 K/20 K = 14.7
Totoal change in entropy for a reversible process is:
zero
If 0.45 kg of water at 100°C is changed by a reversible process to
steam at 100°C, determine the change in entropy of (a) the water, (b) the surroundings, and (c) the universe as a whole. (d) How would your answer differ if the process were irreversible?
The second law of thermodynamics leads us to conclude that:
disorder in the universe is increasing with the passage of time.
If two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other
Zeroth Law
The change in internal energy of a system equals the heat that
flows into or out of it minus the work done by the system (conservation of energy)
First Law
For any real process, the entropy of any isolated system always increases
Second Law
The entropy of a system approaches a constant minimum value as the temperature approaches absolute zero.
Third Law
*absolute zero is impossible to reach through real processes
