Tiêu đề 12. Thermodynamics.pdf ✅

1. Heat is supplied to a di-atomic gas at constant pressure. The ratio of Q :U : W is :- (1) 5 : 3 : 2 (2) 5 : 2 : 3 (3) 7 : 5 : 2 (4) 7 : 2 : 5 2. One mole of an ideal gas having initial volume V, pressure 2P and temperature T undergoes a cyclic process ABCDA as shown below : The net work done in the complete cycle is :- 3. If R = universal gas constant, the amount of heat needed to raise the temperature of 2 mol of an ideal mono atomic gas from 273 K to 373 K when no work is done is– (1) 100 R (2) 150 R (3) 300 R (4) 500 R 4. During an adiabatic process, the pressure of a gas is found to be proportional to the cube of its absolute temperature. The ratio p v C C for the gas is– 5. An ideal heat engine operates on Carnot cycle between 227°C and 127°C. It absorbs 6×104 cal at the higher temperature. The amount of heat converted into work equals to– (1) 4. 8 × 104 cal (2) 3. 5 × 104 cal (3) 1. 6 × 104 cal (4) 1. 2 × 104 cal 6 . One grams of H2 at 27°C is mixed with 16 g of O2 at 37°C. The temperature of the mixture is about – (1) 32°C (2) 27°C (3) 37°C (4) 45°C 7. Three moles of an ideal mono atomic gas perform a cycle as shown in the figure. The gas temperature in different states are: T1 =400 K, T2 = 800 K, T3=2400 K and T4=1200K. The work done by the gas during the cycle is : (1) 10 kJ (2) 20 kJ (3) 5 kJ (4) 8.3 kJ 8. One mole of ideal mono atomic gas ( = 5/3) is mixed with one mole of diatomic gas ( = 7/5). What is  for the mixture ? denotes the ratio of specific heat at constant pressure, to that at constant volume :- (1) 3/2 (2) 23/15 (3) 35/23 (4) 4/3 9. A Carnot's engine whose sink is at a temperature of 300 K has an efficiency of 40%. By how much should the Temperature of the source be increased so as to increase the efficiency to 60%? (1) 250 K (2) 275 K (3) 300 K (4) 325 K 10. Find the amount of work required to be done to increase the temperature of one mole of an ideal gas by 30°C if it is expanding under the condition P V 2/3 (1) 150 J (2) 100 J (3) 50 J (4) 200 J 11. A cyclic process ABCA is shown in PT diagram. When presented on PV, it would A. If both Assertion & Reason are True & The Reason is a correct explanation of the Assertion. Thermodynamics
B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion. C. If Assertion is True but the Reason is False. D. If both Assertion & Reason are False. 12. Assertion :- The specific heat of a given mass of a gas in an adiabatic process is zero and in an isothermal process is infinity. Reason :- Specific heat of gas is directly proportional to change in heat of a system and directly proportional to change in temperature. (1) A (2) B (3) C (4) D 13. When water is heated from 0 to 4° C (1) Cp = C (2) Cp> C (3) Cp< C (4) Cp – C = R 14. An ideal gas is taken through the cycle A → B → C → A, as shown in the figure. What is the change in internal energy? (1) 0 J (2) – 10 J (3) –15 J (4) –20 J 15. An ideal gas is taken through the cycle A → B → C → A, as shown in the figure. If the net heat supplied to the gas in the cycle is 5J, the work done by the gas in the process C → A is :- (1) –5 J (2) –10 J (3) –15 J (4) –20 J 16. An ideal gas undergoes a process 1 → 2 as shown in the figure. The heat supplied and work done in the process are  Q and  W respectively. The ratio  Q :  W is :- (1)  :  – 1 (2)  (3)  – 1 (4)  1  − 17. Five moles of helium are mixed with two moles of hydrogen to form a mixture. Ratio of Cp and Cv of the mixture is : (1) 1.59 (2) 1.53 (3) 1.56 (4) None 18 . The pressure and density of a gas ( = 1. 5changes for (P, ) to (p', ') during adiabatic changes. If '/ = 32, then P'/P will be : (1) 128 (2) 1/128 (3) 32 (4) None 19 . Three processes form a thermodynamic cycle as shown on P-V diagram for an ideal gas. Process 1 → 2 takes place at constant temperature (300K). Process 2 → 3 takes place at constant volume. During this process 40J of heat leaves the system. Process 3 → 1 is adiabatic and temperature T3 is 275 K. Work done by the gas during the process 3 → 1 is :- (1) –40 J (2) –20 J (3) +40 J (4) +20 J 20. An ideal gas expands isothermally from a volumeV1 to V2 and then compressed to original volumeV1 adiabatically. Initial pressure is P1 and final pressure is P3. The total work done is W. Then:- (1) P3> P1, W > 0 (2) P3< P1, W < 0 (3) P3> P1, W < 0 (4) P3 = P1, W = 0 21. The P-V diagram of 2g of helium gas for a certain process A → B is shown in the figure. What is the heat given to the gas during the process A → B?
(1) 4P0V0 (2) 6P0V0 (3) 4.5P0V0 (4) 2P0V0 22. An ideal system can be brought from state A to B through four paths as shown in the figure. The energy given to the system is minimum in : (1) path ACB (2) path ADB (3) path AEB (4) path AFB 23. For a thermodynamic process Q = −50 calorie and W = – 20 calorie. If the initial internal energy is – 30 calorie then final internal energy will be: (1) 191.20 calorie (2) –60 calorie (3) 100 calorie (4) –100 calorie 24. The efficiency of Carnot engine is 50% and temperature of sink is 500 K. If the temperature of source is kept constant and its efficiency is to be raised to 60%, then the required temperature of the sink will be : (1) 600 K (2) 500 K (3) 400 K (4) 100 K 25. The expansion of an ideal gas of mass m at a constant pressure P is given by the straight line B. Then the expansion of the same ideal gas of mass2 m at a pressure 2P is given by the straight line (1) C (2) A (3) B (4) none 26. An ideal gas mixture filled inside a balloon expands according to the relation PV2/3 = constant. The temperature inside the balloon is (1) increasing (2) decreasing (3) constant (4) can’t be said 27. P-V diagram of an ideal gas is as shown in figure. Work done by the gas in the process ABCD is:- (1) 4P0V0 (2) 2P0V0 (3) 3P0V0 (4) P0V0 28. 4.0 g of a gas occupies 22.4 litres at NTP. The specific heat capacity of the gas at constant volume is 5.0 JK–1 mol–1 . If the speed of sound in this gas at NTP is 952 ms–1 , then the specific heat capacity at constant pressure is (Take gas constant R = 8.3 JK–1mol–1 ) (1) 8.5 JK–1mol– 1 (2) 8.0 JK–1mol–1 (3) 7.5 JK–1mol–1 (4) 7.0 JK–1mol–1 29. Two vessels separately contain two ideal gases A and B at the same temperature, the pressure of A being twice that of B. Under such conditions, the density of A is found
to be 1.5 times the density of B. The ratio of molecular weight of A and B is : (1) 1 2 (2) 2 3 (3) 3 4 (4) 4 3 30. One mole of an ideal diatomic gas undergoes a transition from A to B along a path AB as shown in the figure, The change in internal energy of the gas during the transition is : (1) –20 kJ (2) 20 J (3) –12 kJ (4) 20 kJ 31. The P-V diagrams of two different masses m1 and m2 for an ideal gas at constant temperature T is given in figure. Then (1) m1 = m2 (2) m1>m2 (3) m1