Q. In a closed system, if the internal energy increases, what can be said about the heat and work done? (2020)
A.
Heat is added and work is done on the system
B.
Heat is removed and work is done by the system
C.
Heat is added and work is done by the system
D.
No heat exchange occurs
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Solution
According to the first law of thermodynamics, if the internal energy increases, it implies that heat is added to the system and/or work is done on the system.
Correct Answer:
A
— Heat is added and work is done on the system
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Q. In a closed system, if the internal energy increases, what can be said about the work done and heat added? (2020)
A.
Work done is positive and heat added is negative
B.
Work done is negative and heat added is positive
C.
Both work done and heat added are positive
D.
Both work done and heat added are negative
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Solution
According to the first law of thermodynamics, if the internal energy increases, it implies that either work is done on the system or heat is added to the system.
Correct Answer:
C
— Both work done and heat added are positive
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Q. The efficiency of a Carnot engine depends on: (2022)
A.
The temperature of the hot reservoir only
B.
The temperature of the cold reservoir only
C.
The temperatures of both the hot and cold reservoirs
D.
The type of working substance used
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Solution
The efficiency of a Carnot engine is determined by the temperatures of both the hot and cold reservoirs, given by the formula η = 1 - (T_c/T_h).
Correct Answer:
C
— The temperatures of both the hot and cold reservoirs
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Q. The efficiency of a heat engine is defined as the ratio of: (2023)
A.
Work done to heat absorbed
B.
Heat rejected to heat absorbed
C.
Work done to heat rejected
D.
Heat absorbed to work done
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Solution
The efficiency of a heat engine is defined as the ratio of work done by the engine to the heat absorbed from the hot reservoir.
Correct Answer:
A
— Work done to heat absorbed
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Q. The heat capacity at constant volume is defined as: (2023)
A.
C_v = dQ/dT at constant pressure
B.
C_v = dQ/dT at constant volume
C.
C_v = dW/dT at constant volume
D.
C_v = dQ/dP at constant volume
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Solution
The heat capacity at constant volume (C_v) is defined as the amount of heat added to the system divided by the change in temperature at constant volume.
Correct Answer:
B
— C_v = dQ/dT at constant volume
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Q. The specific heat capacity of a substance is defined as the amount of heat required to raise the temperature of: (2023)
A.
1 kg of the substance by 1°C
B.
1 g of the substance by 1°C
C.
1 L of the substance by 1°C
D.
1 mole of the substance by 1°C
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Solution
The specific heat capacity is defined as the amount of heat required to raise the temperature of 1 kg of the substance by 1°C.
Correct Answer:
A
— 1 kg of the substance by 1°C
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Q. The specific heat capacity of a substance is defined as: (2023)
A.
The amount of heat required to raise the temperature by 1 degree Celsius
B.
The amount of heat required to change the phase of a substance
C.
The heat required to raise the temperature of 1 kg of the substance by 1 degree Celsius
D.
The heat required to raise the temperature of 1 mole of the substance by 1 degree Celsius
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Solution
The specific heat capacity is defined as the amount of heat required to raise the temperature of 1 kg of the substance by 1 degree Celsius.
Correct Answer:
C
— The heat required to raise the temperature of 1 kg of the substance by 1 degree Celsius
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Q. The work done by an ideal gas during an isothermal expansion is given by which formula? (2023)
A.
W = PΔV
B.
W = nRT ln(Vf/Vi)
C.
W = ΔU
D.
W = 0
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Solution
The work done by an ideal gas during an isothermal expansion is given by W = nRT ln(Vf/Vi), where Vf and Vi are the final and initial volumes.
Correct Answer:
B
— W = nRT ln(Vf/Vi)
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Q. What happens to the internal energy of an ideal gas during an isothermal expansion? (2021)
A.
Increases
B.
Decreases
C.
Remains constant
D.
Depends on the amount of gas
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Solution
During an isothermal expansion of an ideal gas, the internal energy remains constant because the temperature does not change.
Correct Answer:
C
— Remains constant
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Q. What is the term for the heat required to change a substance from solid to liquid at constant temperature? (2019)
A.
Latent heat of fusion
B.
Latent heat of vaporization
C.
Specific heat
D.
Sensible heat
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Solution
The heat required to change a substance from solid to liquid at constant temperature is called the latent heat of fusion.
Correct Answer:
A
— Latent heat of fusion
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Q. What is the term for the heat required to change a substance from solid to liquid at its melting point? (2019)
A.
Latent heat of fusion
B.
Latent heat of vaporization
C.
Specific heat
D.
Sensible heat
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Solution
The heat required to change a substance from solid to liquid at its melting point is called the latent heat of fusion.
Correct Answer:
A
— Latent heat of fusion
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Q. What is the work done by an ideal gas during an isobaric expansion? (2019)
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Solution
The work done by an ideal gas during an isobaric (constant pressure) expansion is given by W = PΔV.
Correct Answer:
A
— PΔV
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Q. What is the work done on a gas during an isothermal compression? (2019)
A.
Positive
B.
Negative
C.
Zero
D.
Depends on the volume
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Solution
The work done on a gas during isothermal compression is positive, as work is done on the gas to compress it.
Correct Answer:
A
— Positive
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Q. Which law states that the entropy of an isolated system always increases? (2021)
A.
Zeroth law of thermodynamics
B.
First law of thermodynamics
C.
Second law of thermodynamics
D.
Third law of thermodynamics
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Solution
The second law of thermodynamics states that the entropy of an isolated system will always increase over time.
Correct Answer:
C
— Second law of thermodynamics
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Q. Which law states that the entropy of an isolated system never decreases? (2021)
A.
Zeroth law of thermodynamics
B.
First law of thermodynamics
C.
Second law of thermodynamics
D.
Third law of thermodynamics
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Solution
The second law of thermodynamics states that the entropy of an isolated system never decreases over time.
Correct Answer:
C
— Second law of thermodynamics
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Q. Which of the following processes is an example of an isochoric process? (2023)
A.
Heating a gas in a closed container
B.
Compressing a gas in a piston
C.
Expanding a gas against a constant pressure
D.
Cooling a gas at constant pressure
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Solution
An isochoric process is one where the volume remains constant, such as heating a gas in a closed container.
Correct Answer:
A
— Heating a gas in a closed container
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Q. Which of the following statements is true regarding an ideal gas? (2022)
A.
It has no volume
B.
It has no intermolecular forces
C.
It behaves according to the ideal gas law at all temperatures and pressures
D.
Both A and B
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Solution
An ideal gas is considered to have no volume and no intermolecular forces, making option D correct.
Correct Answer:
D
— Both A and B
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