In the 2024-2025 update to heat exchanger design standards (TEMA), which of the following represents the most significant advancement in fouling prediction for industrial heat exchangers?

The correct answer is A: Machine learning-based fouling models using operational data analytics. Recent advancements in heat exchanger design include AI/ML-based predictive fouling models that analyze operational data, surface properties, and fluid characteristics to provide dynamic fouling resistance predictions, replacing traditional static models for improved accuracy.

The dimensionless Stanton number (St = h/(ρ·v·c_p)) in heat transfer represents:

The correct answer is A: Ratio of heat transferred to sensible heat capacity of fluid. St represents the fraction of heat that can be transferred relative to the sensible heat available in flowing fluid per unit area per unit time.

The Colburn analogy relates dimensionless groups for mass, heat, and momentum transfer as:

The correct answer is A: j_D = j_H = f/2, where j represents the Colburn factor. Colburn analogy: j_D = (Sh)/(Re·Sc^(1/3)) ≈ j_H ≈ f/2 for smooth surfaces. Useful for correlating data when only one phenomenon is studied.

The Stefan problem in mass transfer involves:

The correct answer is A: Unsteady diffusion with a moving boundary. The Stefan problem deals with unsteady diffusion with a moving interface, commonly encountered in evaporation from droplets and sublimation processes where the interface position changes with time.

Home

Home › Subjects › Chemical Engineering

Chemical Engineering

Process design, thermodynamics, reactions

117 Q 5 Topics Take Mock Test

Difficulty: All Easy Medium Hard 11–20 of 117

Topics in Chemical Engineering

All Mass Transfer 100 Heat Transfer 100 Fluid Mechanics 100 Chemical Reaction Engineering 100 Thermodynamics 97

Q.11 Hard Thermodynamics

When CO₂ gas at 1 atm is cooled below the sublimation temperature (~195 K), it directly converts to dry ice without passing through liquid phase. This phenomenon is explained by:

A Triple point pressure of CO₂ (5.1 atm) being higher than 1 atm

B Critical temperature of CO₂ being lower than room temperature

C High sublimation enthalpy

D Negative slope of solid-liquid equilibrium line

Correct Answer: A. Triple point pressure of CO₂ (5.1 atm) being higher than 1 atm

EXPLANATION

CO₂ triple point is at 5.1 atm and 216.6 K. At 1 atm, cooling solid CO₂ cannot reach liquid phase because pressure is insufficient. Sublimation occurs directly solid→gas.

Test

Q.12 Hard Thermodynamics

The osmotic pressure of a dilute solution is given by van't Hoff equation: π = iMRT. What does 'i' represent?

A Van't Hoff factor (colligative property modifier)

B Number of moles of solute per liter

C Ideality correction factor

D Activity coefficient of solute

Correct Answer: A. Van't Hoff factor (colligative property modifier)

EXPLANATION

The van't Hoff factor i accounts for ionic dissociation in solution. For non-electrolytes i ≈ 1; for electrolytes i > 1 (e.g., NaCl: i ≈ 2). Essential for colligative property calculations.

Test

Q.13 Hard Thermodynamics

The Clausius-Clapeyron equation relates vapor pressure to temperature. Which assumption is NOT required for its derivation?

A Equilibrium between liquid and vapor phases

B Constant enthalpy of vaporization

C Vapor behaves as an ideal gas

D The system is open

Correct Answer: D. The system is open

EXPLANATION

Clausius-Clapeyron requires phase equilibrium, constant ΔH_vap, ideal gas approximation, but works for closed systems

Test

Q.14 Hard Thermodynamics

For a non-ideal binary mixture, the activity coefficient (γᵢ) deviates from unity when:

A The mixture is dilute

B Intermolecular interactions are significant

C The system is at very low pressure

D The components are structurally similar

Correct Answer: B. Intermolecular interactions are significant

EXPLANATION

Activity coefficients account for non-ideal behavior due to intermolecular forces and molecular size differences

Test

Q.15 Hard Thermodynamics

The Maxwell relation derived from Gibbs free energy (G = H - TS) is:

A (∂S/∂P)_T = (∂V/∂T)_P

B (∂V/∂T)_P = -(∂S/∂P)_T

C (∂P/∂T)_V = (∂S/∂V)_T

D (∂T/∂V)_S = (∂P/∂S)_V

Correct Answer: B. (∂V/∂T)_P = -(∂S/∂P)_T

EXPLANATION

From dG = -SdT + VdP, the Maxwell relation is: (∂V/∂T)_P = -(∂S/∂P)_T

Test

Q.16 Hard Thermodynamics

In a throttling process (Joule-Thomson expansion), for an ideal gas:

A Temperature increases

B Temperature decreases

C Temperature remains constant

D Entropy decreases

Correct Answer: C. Temperature remains constant

EXPLANATION

For ideal gas, enthalpy H depends only on temperature. In throttling (isenthalpic process), H = constant, so T = constant for ideal gas. For real gases, T may change based on Joule-Thomson coefficient.

Test

Q.17 Hard Thermodynamics

The partial molar Gibbs energy at infinite dilution gives the chemical potential μ. For a component in ideal solution:

A μᵢ = μᵢ⁰ + RT ln(xᵢ)

B μᵢ = μᵢ⁰ + RT ln(aᵢ)

C μᵢ = μᵢ⁰ - RT ln(xᵢ)

D μᵢ = μᵢ⁰ + RT ln(γᵢxᵢ)

Correct Answer: A. μᵢ = μᵢ⁰ + RT ln(xᵢ)

EXPLANATION

For ideal solutions, the chemical potential is μᵢ = μᵢ⁰ + RT ln(xᵢ), where xᵢ is the mole fraction. For non-ideal solutions, the activity aᵢ = γᵢxᵢ is used.

Test

Q.18 Hard Thermodynamics

The Maxwell relation that can be derived from Gibbs free energy is:

A (∂S/∂P)ₜ = (∂V/∂T)ₚ

B (∂S/∂P)ₜ = -(∂V/∂T)ₚ

C (∂T/∂P)ₛ = (∂V/∂S)ₚ

D (∂P/∂T)ₛ = (∂S/∂V)ₜ

Correct Answer: B. (∂S/∂P)ₜ = -(∂V/∂T)ₚ

EXPLANATION

From dG = -SdT + VdP, the Maxwell relation is (∂S/∂P)ₜ = -(∂V/∂T)ₚ. This relates entropy-pressure change to volume-temperature change.

Test

Q.19 Hard Chemical Reaction Engineering

For homogeneous gas-phase reaction in batch reactor, if pressure increases at constant volume, what happens to reaction rate for 2A → Products?

A Decreases

B Remains unchanged

C Increases by factor of 4

D Increases by factor of 2

Correct Answer: C. Increases by factor of 4

EXPLANATION

Pressure increase increases concentration proportionally; for 2nd order rate = kC_A², quadrupling concentration increases rate 16-fold; doubling pressure quadruples rate.

Test

Q.20 Hard Chemical Reaction Engineering

In a recycle reactor with recycle ratio R, what is the volume reduction factor compared to PFR for equivalent conversion?

A (1+R)/R

B R/(1+R)

C (1+R)/(1+R²)

D 1 + 1/R

Correct Answer: A. (1+R)/R

EXPLANATION

Recycle reduces required volume by factor (1+R)/R compared to PFR for same conversion and residence time.

Test

1 2 3 4…12

All Subjects & Topics

Govt. Exams

Entrance Exams

Teacher Exams

Subjects

Quick Links

Chemical Engineering