Chemical Engineering questions for GATE and PSU exams are built on a handful of core subjects applied in many ways. Practice spans fluid mechanics, heat transfer, mass transfer, chemical reaction engineering, thermodynamics, process control and instrumentation, and plant design economics. Numerical solutions carry the assumptions written out, because the assumption is usually what separates a correct answer from a plausible one.
The compressibility factor Z for a real gas at high pressure and low temperature typically shows:
Answer: B
At high P and low T, attractive intermolecular forces dominate over repulsion, making Z < 1. This indicates volume is less than ideal gas volume (PV < nRT).
Q.462Hard
In a steam power plant, the Rankine cycle efficiency increases when:
Answer: C
Rankine cycle efficiency η = 1 - T_c/T_h improves with higher boiler temperature/pressure and lower condenser temperature, following Carnot efficiency limits.
Q.463Medium
The second law of thermodynamics can be expressed as:
Answer: B
Second law states ΔS_univ ≥ 0 for isolated systems. Equality holds for reversible processes, inequality for irreversible processes (ΔS_univ > 0).
Q.464Easy
For a binary ideal solution, the total vapor pressure at constant T is given by:
Answer: A
Raoult's law states P_i = P_i°x_i for ideal solutions. Total pressure P = P₁°x₁ + P₂°x₂. This assumes ideal mixing behavior.
Q.465Hard
The chemical potential μᵢ of a component in a mixture relates to partial molar properties by:
Answer: D
All statements define chemical potential from different perspectives. μᵢ is the partial molar Gibbs energy and equals (∂G/∂nᵢ)_{T,P,n_j}.
Q.466Hard
For a spontaneous process in an isolated system, the entropy production σ satisfies:
Answer: B
Entropy production σ = ΔS_total ≥ 0 for isolated systems. σ > 0 for irreversible spontaneous processes; σ = 0 for reversible processes (equilibrium).
Q.467Medium
A heat engine operating between 800 K and 300 K has actual efficiency of 40%. Its carnot efficiency is:
Answer: A
Carnot efficiency = 1 - T_c/T_h = 1 - 800300 = 800500 = 0.625 or 62.5%. Actual efficiency (40%) is always less than Carnot efficiency.
Q.468Medium
The Gibbs phase rule F = C - P + 2 indicates that for a binary system with 2 phases:
Answer: A
F = C - P + 2 = 2 - 2 + 2 = 2, but if we consider only intensive variables at fixed P, then F = 1. Temperature alone determines composition of both phases.
Q.469Easy
During a constant volume process, the first law of thermodynamics simplifies to:
Answer: B
At constant volume, ΔV = 0, so w = -P∫dV = 0. Therefore, ΔU = q + w = q + 0 = q. All heat goes into internal energy change.
Q.470Medium
The reduced temperature T_r and reduced pressure P_r are defined using critical point parameters. A substance at T_r = 0.9 and P_r = 2.0 is classified as:
Answer: B
T_r < 1 means T < T_c (subcritical). P_r = 2 means P > 2P_c (high pressure). This combination indicates compressed liquid state.
Q.471Hard
For a reversible process at constant T and P, the minimum work required (excluding PV work) is:
Answer: B
Useful work (non-PV) available = -ΔG at constant T,P. This represents maximum useful work for spontaneous process or minimum work needed for non-spontaneous process.
Q.472Easy
A gas undergoes an isothermal expansion from 2 L to 5 L at 298 K. If the process is reversible, what is the sign of entropy change for an ideal gas?
Answer: A
For isothermal expansion of an ideal gas, ΔS = nR ln(V_f/V_i) = nR ln(25) > 0. Volume increases, so entropy increases.
Q.473Easy
In the van der Waals equation, the term 'a' represents:
Answer: B
In (P + a/V²)(V - b) = RT, 'a' corrects for intermolecular forces reducing pressure, while 'b' corrects for molecular volume.
