Engineering Board Exam Reviewer · Thermodynamics · medium
One kilogram of air expands isothermally to three times its initial volume. What is the change in entropy? (R = 0.287 kJ/kg· K)
- 0.8610 kJ/K
- 0.3153 kJ/K
- 1.0986 kJ/K
- 0.0000 kJ/K
Answer
B. 0.3153 kJ/K
Solution
S = mR (V2/V1) = 0.287 3 = 0.3153 kJ/K.
More Thermodynamics questions
- One kilogram of water is heated from 300 K to 350 K. What is its change in entropy? (c = 4.187 kJ/kg· K)
- A system receives 500 kJ of heat reversibly at a constant temperature of 400 K. What is its change in entropy?
- One kilogram of air is heated at constant pressure from 300 K to 600 K. What is the change in entropy? (cp = 1.0 kJ/kg· K)
- For the same pressure ratio and initial state, which compression process requires the LEAST work in a steady-flow compressor?
- In a constant-pressure process of a closed system, the heat transferred is equal to the change in:
- In a constant-volume process, the heat transferred is equal to the change in:
- In an isothermal process of an ideal gas, the heat added is equal to:
- One kilogram of air is compressed polytropically (n = 1.3) from 300 K to 400 K. What is the heat transfer? (cv = 0.7186 kJ/kg· K, k = 1.4)
- A gas is compressed from 100 kPa and 1 m3 to 800 kPa and 0.2 m3. What is the polytropic exponent n of the process?
- A gas at 100 kPa and 1 m3 is compressed polytropically (n = 1.3) to 0.5 m3. What is the work done on the gas?