## First And Second Law Of Thermodynamics Multiple Choice Questions And Answers

**Question 1. When a bullet of 6 g mass hits a target at a speed of 400 m · s ^{-1}, 70% of its energy is converted into heat. The value of heat generated is**

- 336 cal
- 80 cal
- 3.36 x 10
^{5}cal - 80000 cal

Answer: 2. 336 cal

**Question 2. Water drops from a height of 40 m in a waterfall. If 75% of its energy is converted to heat and absorbed by the water, the rise in temperature of the water will be**

- 0.035°C
- 0.07°C
- 0.35°C
- 0.7°C

**Answer:** 2. 0.07°C

**Question 3. The amount of work done to convert 1 g of ice at 0°C into steam at 100 °C is**

- 756 J
- 2688 J
- 3024 J
- 171.4 J

**Answer:** 3. 3024 J

**Question 4. 169 J energy is required to transform 1g(1cm³) of water into steam at 1 atm pressure. If the latent heat of vaporization of water is 540 cal · g ^{-1}, the volume of that steam will be**

- 1560 cm³
- 1671 cm³
- 1571cm³
- 1600 cm³

**Answer:** 2. 1671 cm³

**Question 5. A man of mass 90 kg gains 10 ^{5} cal of heat from his food intake. If his digestive ability is 28%, how much height can he climb up to?**

- 1333 m
- 133.3 m
- 13.33 m
- 1.333 m

**Answer:** 2. 133.3 m

**Question 6. Which of the following quantities does not indicate any thermodynamic state of a substance?**

- Volume
- Temperature
- Pressure
- Work

**Answer:** 4. Work

**Question 7. The internal energy of a substance means**

- The kinetic energy of the substance
- The kinetic energy of the molecules of the substance
- The sum of its kinetic and potential energies
- The sum of kinetic and potential energies of the molecules of the substance

**Answer**: 4. The sum of kinetic and potential energies of the molecules of the substance

**Question 8. If the average kinetic energy of the molecules of a certain mass of a gas decreases, then**

- The gas becomes hot
- The gas becomes cold
- The gas expands
- The gas contracts

**Answer**: 2. The gas becomes cold

**Question 9. If the volume of a gas of a certain mass changes from 1 L to 0.5 L at a constant pressure of 10 ^{5} N · m^{-2}, work done by the gas will be**

- 50000 J
- -50000 J
- 50 J
- -50 J

**Answer:** 4. -50 J

**Question 10. The internal energy of a system is U _{1}. In a process, work done by the system is W, and heat accepted by the system is Q. At the end of the process, the internal energy of the system is**

- U
_{1}+ Q-W - U
_{1}-Q+W - U
_{1}+ Q+W - U
_{1}– Q-W

**Answer:** 1. U_{1} + Q-W

**Question 11. The work done by an ideal gas at constant temperature is 10 J. The amount of heat gained in this process is**

- 10Cal
- 2.38 cal
- Zero
- Data insufficient

**Answer:** 2. 2.38 cal

**Question 12. The work done by an ideal gas at constant pressure is 10 J. The amount of heat gained in this process is**

- 10cal
- 2.38 cal
- zero
- Data insufficient

**Answer:** 4. Data insufficient

**Question 13. If the internal energy U and the work W are expressed in unit of J and the heat is expressed in unit of cal, the first law of thermodynamics will be [here J = Joule’s equivalent]**

- dQ = dU+\(\frac{dW}{J}\)
- dQ = dU+JdW
- JdQ = dU+dW
- \(\frac{dQ}{J}\)

**Answer:** 3. JdQ = dU+dW

**Question 14. C _{v} = 5/2, for 1 mol of any diatomic ideal ga of the ratio of the two specific heats is \(\left[\frac{C_p}{C_v}=\gamma\right]\) of the gas is**

- \(\frac{4}{3}\)
- \(\frac{5}{3}\)
- \(\frac{7}{3}\)
- \(\frac{7}{5}\)

**Answer:** 4. \(\frac{7}{5}\)

**Question 15. If R = 2 cal · mol ^{-1} · °C^{-1} and hydrogen is assumed to be an ideal gas, specific heat1 of that gas at constant pressure will be**

- 7 cal g °C
^{-1} - 5 cal g °C
^{-1} - 3.5 cal · g
^{-1 ·}°C^{-1} - 1.25 cal · g
^{-1}· °C^{-1}

**Answer:** 3. 3.5 cal · g^{-1} · °C^{-1}

**Question 16. Work done becomes zero**

- At constant pressure
- At constant volume
- In isothermal process
- In adiabatic process

**Answer:** 2. At constant volume

**Question 17. The change in internal energy of an ideal gas becomes zero**

- At constant pressure
- At constant volume
- In isothermal process
- In adiabatic process

**Answer:** 3. In isothermal process

**Question 18. The process in which changes in pressure, volume and temperature occur simultaneously is**

- Isobaric
- Isochoric
- Isothermal
- Adiabatic

**Answer:** 4. Adiabatic

**Question 19. It is observed by comparing the specific heats of all solid, liquid, and gaseous substances that**

- Specific heat of water is the highest
- Specific heats of hydrogen and helium are higher than that of water
- All gases have specific heat higher than that of water
- All liquid and gases have specific heats higher than that of water

**Answer:** 2. Specific heats of hydrogen and helium are higher than that of water

**Question 20. In an adiabatic expansion, the change in internal energy of 10 mol of a gas is 100 J. What is the amount of work done by the gas?**

- -100 J
- 100 J
- 1000 J
- -1000 J

**Answer:** 2. 100 J

**Question 21. Which of the following relations does an ideal gas follow in an adiabatic process?**

- pV = RT
- pV
^{γ}= constant - \(\left(p+\frac{a}{V^2}\right)(V-b)=R T\)
- \(p V^{\gamma-1}\)= constant

**Answer:** 2. pV^{γ} = constant

**Question 22. The slope of an isothermal curve is always**

- Same as that of an adiabatic curve
- Greater than that of an adiabatic curve
- Less than that of an adiabatic curve
- Not derivable

**Answer:** 3. Less than that of an adiabatic curve

**Question 23. ‘Heat cannot transmit from a body at lower temperature to a body at higher temperature on its own’— which law is this statement derived from?**

- First law of thermodynamics
- Second law of thermodynamics
- Law of conservation of momentum
- Law of conservation of mass

**Answer:** 2. Second law of thermodynamics

**Question 24. A system can go from state A to state B in two different processes 1 and 2. If the change in internal energy in the two cases are ΔU _{1} and ΔU_{2}, respectively, then**

- \(\Delta U_1<\Delta U_2\)
- \(\Delta U_1>\Delta U_2\)
- \(\Delta U_1=\Delta U_2\)
- The relation between \(\Delta U_1 and \Delta U_1\) is uncertain

**Answer:** 3. \(\Delta U_1=\Delta U_2\)

**Question 25. In a given process of an ideal gas, dW = 0 and dQ < 0. Then for the gas**

- The temperature will decrease
- The volume will increase
- The pressure will remain constant
- The temperature will increase

**Answer:** 1. The temperature will decrease

**Question 26. 5.6 L of helium gas at STP is adiabatically compressed to 0.7 L. Taking the initial temperature to be T _{1}, the work done in the process is**

- \(\frac{9}{8} R T_1\)
- \(\frac{3}{2} R T_1\)
- \(\frac{15}{8} R T_1\)
- \(\frac{9}{2} R T_1\)

**Answer:** 1. \(\frac{9}{8} R T_1\)

**Question 27. During the process, shown work done by the system**

- Continuously increases
- Continuously decreases
- First increases then decreases
- First decreases then increases

**Answer:** 1. Continuously increases

**Question 28. When a system is taken from the state i to the state f along the path if, it is found that Q = 50 cal and w= 20 cal. Along the path ibf, Q = 36 cal. W along the path is**

- 6 cal
- 16 cal
- 66 cal
- 14 cal

**Answer:** 1. 6 cal

**Question 29. A Carnot engine, having an efficiency of \(\eta=\frac{1}{10}\) as heat engine is used as a refrigerator. If the work done on the system is 10 J, the amount of energy absorbed from the reservoir at lower temperature is**

- 99 J
- 90 J
- 1J
- 100 J

**Answer:** 2. 90 J

**Question 30. The efficiency of a Carnot heat engine working between temperatures 127°C and 27°C is**

- \(\frac{27}{127}\)
- \(\frac{100}{127}\)
- \(\frac{300}{400}\)
- \(\frac{100}{400}\)

**Answer:** 4. \(\frac{100}{400}\)

**Question 31. The efficiency of an ideal heat engine is**

- 0%
- 50%
- 100%
- None

**Answer:** 3. 100%

**Question 32. Coefficient of performance of a machine is**

- \(\frac{\text { output }}{\text { input }}\)
- \(\frac{\text { input }}{\text { output }}\)
- \(\frac{0}{\text { input }}\)
- None

**Answer:** 1. \(\frac{\text { output }}{\text { input }}\)

**Question 33. Even Carnot engine cannot give 100% efficiency, because we cannot**

- Prevent radiation
- Find ideal sources
- Reach absolute zero temperature
- Eliminate friction

**Answer:** 3. Reach absolute zero temperature

**In this type of question, more than one option are correct.**

**Question 34. C _{v} and C_{p} denote the molar-specific heat capacities of a gas at constant volume and constant pressure, respectively then,**

- (C
_{p}– C_{v}) larger for A diatomic ideal gas than for a monatomic ideal gas - (C
_{p}+ C_{v}) is larger for a diatomic ideal gas than for a monatomic ideal gas - C
_{p}/C_{v}is a target for a diatomic ideal gas than for a monatomic ideal gas - C
_{p}x C_{v}is larger for a diatomic ideal gas than for a monatomic, ideal gas

**Answer:**

2. (C_{p} + C_{v}) is larger for a diatomic ideal gas than for a monatomic ideal gas

4. C_{p} x C_{v} is larger for a diatomic ideal gas than for a monatomic, ideal gas

**Question 35. Shows the p- V plot of an ideal gas taken through a cycle ABCDA. Part ABC is a semicircle and CDA is half of an ellipse. Then**

- The process during the path A → B is isothermal
- Heat flows out of the gas during the path B → C → D
- Work done during the path A → B → C in zero
- Positive work is done by the gas in the cycle ABCDA

**Answer:**

1. The process during the path A → B is isothermal

2. Heat flows out of the gas during the path B → C→ D

**Question 36. 1 mol of an ideal gas in initial state A undergoes a cyclic process ABCA, as shown. Its pressure at A is p _{0}. Choose the correct options from the following**

- Internal energies at a and b are the same
- Work done by the gas in process ab is p
_{0}v_{0}ln 4 - Pressure at C is \(\frac{p_0}{4}\)
- Temperature at C is \(\frac{t_0}{4}\)

**Answer:**

1. Internal energies at a and b are the same

3. Pressure at c is \(\frac{p_0}{4}\)

**Question 37. In the cyclic process shown, ΔU _{1} and ΔU_{2} represent the change in internal energy in processes A and B, respectively. If ΔQ is the net heat given to the system in the process and ΔW is the work done by the system in the process. then**

- \(\Delta U_1+\Delta U_2=0\)
- \(\Delta U_1-\Delta U_2=0\)
- \(\Delta Q-\Delta W=0\)
- \(\Delta Q+\Delta W=0\)

**Answer:**

1. \(\Delta U_1+\Delta U_2=0\)

3. \(\Delta Q-\Delta W=0\)

**Question 38. Shows the pV diagrams for a Carnot cycle. In this diagram**

- Curve AB represents the isothermal process and BC adiabatic process
- Curve AB represents the adiabatic process and BC isothermal process
- Curve CD represents the isothermal process and DA adiabatic process
- Curve CD represents the adiabatic process and DA isothermal process

**Answer:**

2. Curve AB represents the adiabatic process and BC isothermal process

4. Curve CD represents the adiabatic process and DA isothermal process