MCQOPTIONS
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MCQOPTIONS
This section includes 8 Mcqs, each offering curated multiple-choice questions to sharpen your Thermodynamics Questions and Answers knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
A glass jar is filled with saturated water at 500 kPa of quality 25%, and a tight lid is put on. Now it is cooled to -10°C. What is the mass fraction of solid at this temperature? |
| A. | 99.98% |
| B. | 98.98% |
| C. | 93.98% |
| D. | 95.98% |
| Answer» B. 98.98% | |
| 2. |
A thermal reservoir at 538°C is brought into thermal communication with another thermal reservoir at 260°C, and as a result 1055 kJ of heat is transferred only from the higher to lower temperature reservoir. Determine the change in entropy of the universe due to the exchange of heat between these two thermal reservoirs. |
| A. | 0.378182 kJ/K |
| B. | 0.478182 kJ/K |
| C. | 0.578182 kJ/K |
| D. | 0.678182 kJ/K |
| Answer» E. | |
| 3. |
Two kilograms of water at 120°C with a quality of 25% has its temperature raised by 20°C in a constant volume process. What is the new specific entropy? |
| A. | 3.01517 kJ/kg.K |
| B. | 4.01517 kJ/kg.K |
| C. | 5.01517 kJ/kg.K |
| D. | 7.01517 kJ/kg.K |
| Answer» C. 5.01517 kJ/kg.K | |
| 4. |
Calculate the change in entropy if 1 kg of saturated liquid at 30°C is converted into superheated steam at 1 bar and 200°C . |
| A. | 5.3973 kJ/K |
| B. | 6.3973 kJ/K |
| C. | 7.3973 kJ/K |
| D. | none of the mentioned |
| Answer» D. none of the mentioned | |
| 5. |
A foundry form box with 25 kg of 200°C hot sand is dropped into a bucket with 50 L water at 15°C. Assuming there is no heat transfer with the surroundings and no boiling away of water, calculate the net entropy change for the process. |
| A. | 2.37 kJ/K |
| B. | 2.47 kJ/K |
| C. | 2.57 kJ/K |
| D. | 2.67 kJ/K |
| Answer» D. 2.67 kJ/K | |
| 6. |
A slab of concrete, 5 × 8 × 0.3 m, is used as a thermal storage mass in a house. The slab cools overnight from 23°C to 18°C in an 18°C house, find the net entropy change associated with this process? |
| A. | 0.4 kJ/K |
| B. | 1.4 kJ/K |
| C. | 2.4 kJ/K |
| D. | 3.4 kJ/K |
| Answer» E. | |
| 7. |
In a Carnot engine working on ammonia, the high temperature is 60°C and as QH is received, the ammonia changes from saturated liquid to saturated vapor. The ammonia pressure at low temperature is 190 kPa. Find the entropy. |
| A. | 4.6577 kJ/kg K |
| B. | 5.6577 kJ/kg K |
| C. | 6.6577 kJ/kg K |
| D. | 7.6577 kJ/kg K |
| Answer» B. 5.6577 kJ/kg K | |
| 8. |
A car uses power of 25 hp for a one hour in a round trip. A thermal efficiency of 35% can be assumed? Find the change in entropy if we assume ambient at 20°C? |
| A. | 554.1 kJ/K |
| B. | 654.1 kJ/K |
| C. | 754.1 kJ/K |
| D. | 854.1 kJ/K |
| Answer» C. 754.1 kJ/K | |