# First Law Of Thermodynamics; 05.05.2020, Time : 11am To 12 Noon

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Dr. K
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Quizzes Created: 1 | Total Attempts: 85
Questions: 10 | Attempts: 85

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Created by
Dr. K. S. Prakash
Assistant Professor of Chemistry
Bharathidasan Govt. College for Women (Autonomous)
Puducherry.

• 1.

### The first law of thermodynamics is basically the same as which law from physics?

• A.

Newton's first law

• B.

The law of conservation of energy

• C.

Newton's second law

• D.

The law of conservation of momentum

B. The law of conservation of energy
Explanation
The first law of thermodynamics states that energy cannot be created or destroyed, only transferred or converted from one form to another. This is essentially the same principle as the law of conservation of energy in physics, which states that the total energy of a closed system remains constant over time. Both laws emphasize the fundamental concept that energy is conserved in all physical processes.

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• 2.

### The SI unit for measuring heat is the

• A.

Pascal

• B.

Newton

• C.

Calorie

• D.

Joule

D. Joule
Explanation
The SI unit for measuring heat is the Joule. This unit is used to measure energy transfer, including heat. The Joule is defined as the amount of energy transferred when a force of one newton is applied over a distance of one meter. It is commonly used in scientific and engineering fields to quantify heat transfer, as well as other forms of energy such as work and mechanical energy. The pascal is a unit of pressure, the newton is a unit of force, and the calorie is a unit of energy commonly used in nutrition.

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• 3.

### If the volume of the system increases, the work done on the system is positive. true or false?

• A.

True

• B.

False

B. False
Explanation
If the volume of the system increases, it means that the system is expanding. According to the sign convention, work done on the system is considered positive when the system contracts or decreases in volume. Therefore, if the volume of the system increases, the work done on the system would be negative, not positive. Hence, the correct answer is false.

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• 4.

### What is constant in an isothermal process?

• A.

PV

• B.

P/T

• C.

V/T

• D.

Heat

A. PV
Explanation
In an isothermal process, the temperature remains constant. According to the ideal gas law, PV = nRT, where P is the pressure, V is the volume, n is the number of moles of gas, R is the ideal gas constant, and T is the temperature. Since the temperature is constant in an isothermal process, the product of PV also remains constant. Therefore, PV is the correct answer as it represents the constant in an isothermal process.

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• 5.

### The law of conservation of energy states that the total energy of an isolated system is ________

Constant
Explanation
The law of conservation of energy states that the total energy of an isolated system remains constant. This means that energy cannot be created or destroyed, but it can only be transferred or transformed from one form to another within the system. This principle is based on the understanding that energy is a fundamental quantity in nature and its total amount in a closed system remains unchanged over time.

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• 6.

### Total entropy change for all spontaneous process -----------

Positive, +
Explanation
The total entropy change for all spontaneous processes is positive. This is because entropy is a measure of the disorder or randomness in a system, and spontaneous processes tend to increase the disorder of a system. Therefore, the entropy change for these processes is positive.

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• 7.

### What is the equation for the first law of thermodynamics?

• A.

U=Q+W

• B.

U=Q-W

• C.

U=-Q+W

• D.

U+Q+W=0

A. U=Q+W
Explanation
The equation U=Q+W represents the first law of thermodynamics, which states that the internal energy (U) of a system is equal to the heat (Q) added to the system and the work (W) done on the system. This equation shows the conservation of energy in a thermodynamic process, where the change in internal energy is determined by the heat added to the system and the work done on or by the system.

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• 8.

### Which of the following represents the energy in storage?

• A.

Heat

• B.

Work

• C.

Internal energy

• D.

None of the mentioned

C. Internal energy
Explanation
Internal energy represents the energy in storage. It refers to the total energy contained within a system, including both the kinetic and potential energy of its particles. It encompasses the energy associated with the random motion and interactions of the particles within the system. Therefore, internal energy is a representation of the energy stored within a system.

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• 9.

### By first law of thermodynamics

• A.

Q=ΔE-W

• B.

Q=ΔE+W

• C.

Q=-ΔE-W

• D.

Q=-ΔE+W

B. Q=ΔE+W
Explanation
The correct answer is Q=ΔE+W. According to the first law of thermodynamics, the change in internal energy (ΔE) of a system is equal to the heat added to the system (Q) minus the work done by the system (W). Therefore, the correct equation is Q=ΔE+W, where Q represents the heat added to the system, ΔE represents the change in internal energy, and W represents the work done by the system.

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• 10.

### Which of the following an be considered as the definition of energy?

• A.

Q=ΔE+W

• B.

Q-W=ΔE

• C.

First law of thermodynamics

• D.

All of the mentioned

D. All of the mentioned
Explanation
All of the mentioned options can be considered as definitions of energy. The equation Q = ΔE + W represents the conservation of energy, where Q is the heat added to a system, ΔE is the change in internal energy, and W is the work done on or by the system. Q - W = ΔE is a rearrangement of the first equation, showing that the change in internal energy is equal to the heat added minus the work done. The first law of thermodynamics states that energy cannot be created or destroyed, only transferred or converted from one form to another. Therefore, all of these options provide a definition or explanation of energy.

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• Mar 21, 2023
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• May 04, 2020
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