A. An open system of constant composition
B. A closed system of constant composition
C. An open system with changes in composition
D. A closed system with changes in composition
✅ The correct answer is option D.
Thermodynamics MCQs
272. First law of thermodynamics is mathematically stated as
A. dQ = dE + dW
B. dQ = dE – dW
C. dE = dQ + dW
D. dW = dQ + dE
✅ The correct answer is option A.
273. Compound having large heat of formation is
A. More stable
B. Less stable
C. Not at all stable (like nascent O₂)
D. Either more or less stable ; depends on the compound
✅ The correct answer is option A.
274. As the temperature is lowered towards the absolute zero, the value of the quantity (∂ΔF/∂T) approaches
A. Zero
B. Unity
C. Infinity
D. None of these
✅ The correct answer is option A.
275. Change of state namely evaportation condensation, freezing and melting is an __________ process.
A. Isothermal
B. Adiabatic
C. Isobaric
D. Isochoric
✅ The correct answer is option A.
276. When a gas is subjected to adiabatic expansion, it gets cooled due to
A. Decrease in velocity
B. Decrease in temperature
C. Decrease in kinetic energy
D. Energy spent in doing work
✅ The correct answer is option D.
277. Generation of heat by friction is an example of a/an __________ change.
A. Isothermal
B. Irreversible
C. Adiabatic
D. Reversible
✅ The correct answer is option B.
278. The rate at which a substance reacts is proportional to its active mass and the rate of a chemical reaction is proportional to the product of active masses of the reacting substances. This is the
A. Lewis-Randall rule
B. Statement of Vant-Hoff equation
C. Le-Chatelier’s principle
D. None of these
✅ The correct answer is option D.
279. Maximum work that could be secured by expanding the gas over a given pressure range is the __________ work.
A. Isothermal
B. Adiabatic
C. Isentropic
D. None of these
✅ The correct answer is option A.
280. Fugacity of a component in an ideal gas mixture is euqal to the partial pressure of that component in the mixture. The fugacity of each component in a stable homogeneous solution at contant pressure and temperature __________ as its mole fraction increases.
A. Decreases
B. Decreases exponentially
C. Increases
D. Remains constant
✅ The correct answer is option C.