Q. According to the first law of thermodynamics, what happens to the internal energy of a system when heat is added and work is done by the system?
A.
Increases
B.
Decreases
C.
Remains constant
D.
Cannot be determined
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Solution
The first law states ΔU = Q - W. If heat Q is added and work W is done by the system, the internal energy decreases.
Correct Answer:
B
— Decreases
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Q. According to the kinetic theory of gases, what is the relationship between temperature and the average kinetic energy of gas molecules?
A.
Directly proportional
B.
Inversely proportional
C.
Independent
D.
Exponential
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Solution
The average kinetic energy of gas molecules is directly proportional to the absolute temperature of the gas.
Correct Answer:
A
— Directly proportional
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Q. According to the kinetic theory, what is the relationship between pressure and the number of gas molecules in a container?
A.
Pressure is independent of the number of molecules
B.
Pressure decreases with more molecules
C.
Pressure increases with more molecules
D.
Pressure is inversely proportional to the number of molecules
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Solution
According to the kinetic theory, pressure is directly proportional to the number of gas molecules in a container, assuming temperature and volume are constant.
Correct Answer:
C
— Pressure increases with more molecules
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Q. According to the third law of thermodynamics, what happens as the temperature approaches absolute zero?
A.
Entropy approaches zero
B.
Entropy approaches infinity
C.
Internal energy approaches zero
D.
All molecular motion stops
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Solution
The third law states that as the temperature approaches absolute zero, the entropy of a perfect crystal approaches zero.
Correct Answer:
A
— Entropy approaches zero
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Q. If a metal rod is heated at one end, what happens to the temperature of the other end over time?
A.
It remains constant
B.
It decreases
C.
It increases
D.
It fluctuates
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Solution
The temperature of the other end of the rod will increase over time due to conduction as heat is transferred along the rod.
Correct Answer:
C
— It increases
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Q. If the entropy of a system increases, what can be inferred about the system?
A.
It is losing energy
B.
It is becoming more ordered
C.
It is becoming more disordered
D.
It is in thermal equilibrium
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Solution
An increase in entropy indicates that the system is becoming more disordered.
Correct Answer:
C
— It is becoming more disordered
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Q. If the temperature of a gas increases, what happens to its volume at constant pressure?
A.
It decreases
B.
It remains the same
C.
It increases
D.
It becomes zero
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Solution
According to Charles's Law, if the temperature of a gas increases at constant pressure, its volume increases.
Correct Answer:
C
— It increases
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Q. If the temperature of a gas increases, what happens to its volume if the pressure remains constant?
A.
It decreases
B.
It remains the same
C.
It increases
D.
It becomes zero
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Solution
According to Charles's Law, if the pressure is constant, the volume of a gas increases as its temperature increases.
Correct Answer:
C
— It increases
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Q. If the volume of a gas is halved at constant temperature, what happens to the pressure?
A.
It remains the same
B.
It halves
C.
It doubles
D.
It quadruples
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Solution
According to Boyle's law, pressure is inversely proportional to volume at constant temperature. If the volume is halved, the pressure doubles.
Correct Answer:
C
— It doubles
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Q. In a Carnot engine operating between 300 K and 600 K, what is the maximum efficiency?
A.
50%
B.
60%
C.
33.33%
D.
100%
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Solution
Efficiency = 1 - (T_cold/T_hot) = 1 - (300/600) = 0.5 or 50%.
Correct Answer:
B
— 60%
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Q. In a Carnot engine operating between 500 K and 300 K, what is the maximum efficiency?
A.
40%
B.
60%
C.
50%
D.
20%
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Solution
Efficiency = 1 - (Tc/Th) = 1 - (300/500) = 0.4 or 40%.
Correct Answer:
B
— 60%
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Q. In a Carnot engine, if the hot reservoir is at 500 K and the cold reservoir is at 300 K, what is the maximum efficiency?
A.
40%
B.
60%
C.
50%
D.
20%
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Solution
The maximum efficiency of a Carnot engine is given by 1 - (T_c/T_h), which is 1 - (300/500) = 0.4 or 40%.
Correct Answer:
B
— 60%
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Q. In a heat engine, if the input heat is 1000 J and the work done is 300 J, what is the efficiency of the engine?
A.
30%
B.
70%
C.
50%
D.
10%
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Solution
Efficiency is calculated as η = (Work output / Heat input) * 100%. Here, η = (300 J / 1000 J) * 100% = 30%.
Correct Answer:
A
— 30%
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Q. In a heat engine, if the input heat is 800 J and the output work is 300 J, what is the efficiency?
A.
0.375
B.
0.5
C.
0.25
D.
0.625
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Solution
Efficiency = Work output / Heat input = 300 J / 800 J = 0.375 or 37.5%.
Correct Answer:
A
— 0.375
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Q. In a heat engine, what is the purpose of the heat reservoir?
A.
To absorb heat
B.
To release heat
C.
To convert heat to work
D.
To increase efficiency
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Solution
The heat reservoir serves as a source of thermal energy that the heat engine absorbs heat from to perform work.
Correct Answer:
A
— To absorb heat
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Q. In a heat engine, what is the purpose of the heat sink?
A.
To absorb heat from the engine
B.
To release heat to the environment
C.
To increase efficiency
D.
To store energy
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Solution
The heat sink in a heat engine is used to release excess heat to the environment, allowing the engine to operate efficiently.
Correct Answer:
B
— To release heat to the environment
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Q. In a heat engine, what is the work done equal to?
A.
Heat input minus heat output
B.
Heat output minus heat input
C.
Total heat energy
D.
Change in internal energy
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Solution
The work done by a heat engine is equal to the heat input minus the heat output.
Correct Answer:
A
— Heat input minus heat output
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Q. In an ideal gas, if the temperature is doubled while keeping the volume constant, what happens to the pressure?
A.
It halves
B.
It doubles
C.
It quadruples
D.
It remains the same
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Solution
According to Gay-Lussac's law, pressure is directly proportional to temperature when volume is constant. Therefore, if the temperature is doubled, the pressure also doubles.
Correct Answer:
B
— It doubles
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Q. In an ideal gas, what happens to the pressure if the volume is halved while keeping the temperature constant?
A.
Pressure doubles
B.
Pressure halves
C.
Pressure remains the same
D.
Pressure quadruples
Show solution
Solution
According to Boyle's Law, if the volume is halved at constant temperature, the pressure doubles.
Correct Answer:
A
— Pressure doubles
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Q. In an ideal gas, what is the relationship between pressure and temperature at constant volume?
A.
Directly proportional
B.
Inversely proportional
C.
No relationship
D.
Exponential relationship
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Solution
According to Gay-Lussac's Law, pressure is directly proportional to temperature at constant volume.
Correct Answer:
A
— Directly proportional
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Q. In an isothermal process, what remains constant?
A.
Pressure
B.
Volume
C.
Temperature
D.
Internal energy
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Solution
In an isothermal process, the temperature of the system remains constant.
Correct Answer:
C
— Temperature
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Q. In which process does the entropy of a system decrease?
A.
Isothermal expansion
B.
Adiabatic compression
C.
Isobaric heating
D.
Isothermal compression
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Solution
In adiabatic compression, the entropy of the system decreases as work is done on the gas, increasing its temperature without heat exchange.
Correct Answer:
B
— Adiabatic compression
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Q. What does the second law of thermodynamics state about entropy?
A.
Entropy can decrease in an isolated system
B.
Entropy remains constant in reversible processes
C.
Entropy of an isolated system always increases
D.
Entropy is a measure of energy
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Solution
The second law of thermodynamics states that the entropy of an isolated system always increases over time.
Correct Answer:
C
— Entropy of an isolated system always increases
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Q. What happens to the entropy of a system when heat is added at a constant temperature?
A.
It decreases
B.
It remains the same
C.
It increases
D.
It becomes zero
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Solution
When heat is added to a system at constant temperature, the entropy of the system increases, as entropy is a measure of disorder.
Correct Answer:
C
— It increases
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Q. What happens to the volume of a gas when it is heated at constant pressure?
A.
It decreases
B.
It remains the same
C.
It increases
D.
It fluctuates
Show solution
Solution
According to Charles's Law, the volume of a gas increases when it is heated at constant pressure.
Correct Answer:
C
— It increases
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Q. What is entropy a measure of?
A.
Energy
B.
Disorder
C.
Temperature
D.
Pressure
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Solution
Entropy is a measure of disorder or randomness in a system, indicating the number of ways a system can be arranged.
Correct Answer:
B
— Disorder
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Q. What is the average kinetic energy of a gas molecule at temperature 300 K?
A.
1.24 x 10^-21 J
B.
4.14 x 10^-21 J
C.
6.21 x 10^-21 J
D.
2.07 x 10^-21 J
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Solution
The average kinetic energy of a gas molecule is given by the formula KE = (3/2)kT, where k is the Boltzmann constant (1.38 x 10^-23 J/K) and T is the temperature in Kelvin. KE = (3/2)(1.38 x 10^-23)(300) = 6.21 x 10^-21 J.
Correct Answer:
B
— 4.14 x 10^-21 J
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Q. What is the change in entropy when 1 kg of ice at -10°C is converted to water at 0°C?
A.
0 J/K
B.
333 J/K
C.
1000 J/K
D.
2000 J/K
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Solution
The change in entropy during the melting of ice is approximately 333 J/K.
Correct Answer:
B
— 333 J/K
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Q. What is the change in entropy when 1 kg of water at 100°C is converted to steam at 100°C?
A.
2260 J/K
B.
100 J/K
C.
540 J/K
D.
0 J/K
Show solution
Solution
The change in entropy (ΔS) for the phase change is calculated as ΔS = Q/T = 2260 J / 373 K = 6.06 J/K, but for 1 kg, it is 2260 J/K.
Correct Answer:
A
— 2260 J/K
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Q. What is the change in entropy when 1 mole of an ideal gas expands isothermally from 10 L to 20 L at 300 K?
A.
0.5 J/K
B.
1.0 J/K
C.
1.5 J/K
D.
2.0 J/K
Show solution
Solution
ΔS = nR ln(Vf/Vi) = 1 * 8.314 * ln(20/10) = 1.0 J/K.
Correct Answer:
B
— 1.0 J/K
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