Mechanical Engineering - MCQ Practice Questions

Which of the following is NOT a state function in thermodynamics?

An ideal gas expands adiabatically from initial state (P₁=10 bar, V₁=0.5 m³) to final volume V₂=1.5 m³. If γ=1.4, find the final pressure approximately.

The specific heat capacity at constant volume (Cv) for a monoatomic ideal gas is:

A carnot engine operates between 600 K and 300 K. The maximum possible efficiency is:

For a closed system undergoing a cyclic process, which statement is correct?

The dryness fraction (quality) of steam at a state where specific enthalpy is 2500 kJ/kg, given hf=417.36 kJ/kg and hfg=2257.9 kJ/kg, is approximately:

A substance has a critical temperature Tc=647 K and critical pressure Pc=22.1 MPa. This is most likely:

An open system (control volume) has mass entering at 50 kg/s with specific enthalpy 200 kJ/kg and mass leaving at 50 kg/s with specific enthalpy 350 kJ/kg. The rate of work done ON the system is 2 MW. Neglecting KE and PE changes, the rate of heat transfer is:

For a polytropic process PVⁿ = constant with n=1.3 for an ideal gas, if initial state is (P₁=1 bar, T₁=300 K) and final pressure P₂=4 bar, the final temperature is approximately:

The enthalpy of vaporization (latent heat) of water at 100°C is 2257 kJ/kg. This represents:

A reciprocating compressor compresses air from 1 bar, 300 K to 10 bar. If the process follows PVⁿ = constant with n=1.25, what is the specific work required per kg of air? (R=287 J/kg·K)

According to the First Law of Thermodynamics for a closed system: dU = δQ - δW. If a gas is compressed adiabatically, which is true?

A throttling process (Joule-Thomson expansion) through a valve is characterized by:

The relationship between specific heats Cp - Cv for an ideal gas is:

In a Otto cycle (spark ignition engine), which process is isochoric (constant volume)?

For a reversible process in an isolated system (adiabatic, no work), the entropy change is:

The van der Waals equation accounts for real gas behavior with correction terms. Which statement is correct?

A Rankine cycle operates between 8 MPa (saturation temp ≈ 295°C) and 0.01 MPa (saturation temp ≈ 45°C). The isentropic efficiency of the turbine is 85%. If inlet enthalpy to turbine is 2800 kJ/kg and exit enthalpy for isentropic expansion is 2300 kJ/kg, the actual exit enthalpy is:

Which of the following statements about entropy is INCORRECT?

A heat engine operates between two thermal reservoirs at temperatures 600 K and 300 K. What is the maximum possible efficiency of this engine?