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:

The correct answer is B: Subcritical but compressed liquid. T_r 2P_c (high pressure). This combination indicates compressed liquid state.

Which of the following materials would be most suitable for a heat sink application requiring high thermal conductivity and low cost?

The correct answer is B: Aluminum alloy (k = 160 W/m·K). Aluminum alloys offer an excellent balance of thermal conductivity (160 W/m·K, sufficient for most applications), cost-effectiveness, light weight, corrosion resistance, and ease of machining. While copper has higher conductivity, aluminum's cost-benefit ratio is superior for heat sink applications.

The Helmholtz free energy (A = U - TS) is the maximum useful work available at:

The correct answer is A: Constant temperature and volume. Helmholtz free energy is defined at constant T and V. ΔA_max = W_useful (non-PV work)

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

The correct answer is C: Increases by factor of 4. Pressure increase increases concentration proportionally; for 2nd order rate = kC_A², quadrupling concentration increases rate 16-fold; doubling pressure quadruples rate.

A heat engine operates between 600 K and 300 K. What is the maximum theoretical efficiency (Carnot efficiency)?

The correct answer is A: 50%. η_Carnot = 1 - (T_C/T_H) = 1 - (300/600) = 0.5 = 50%

Home

Home › Subjects › Chemical Engineering › Mass Transfer

Chemical Engineering
Mass Transfer

Process design, thermodynamics, reactions

32 Q 5 Topics Take Mock Test

Difficulty: All Easy Medium Hard 11–20 of 32

Topics in Chemical Engineering

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

Q.11 Hard Mass Transfer

For simultaneous diffusion and reaction (fast reaction regime) in a porous catalyst, the effectiveness factor η approaches:

A 1 (no limitation)

B 1/Φ where Φ is the Thiele modulus

C 0.3 × 1/Φ² (approximately)

D Φ² (for diffusion-limited regime)

Correct Answer: B. 1/Φ where Φ is the Thiele modulus

EXPLANATION

In the fast reaction regime where diffusion limits the overall rate, η ≈ 1/Φ for spherical pellets, indicating severe internal diffusion limitations.

Test

Q.12 Hard Mass Transfer

In gas-solid adsorption, the Langmuir isotherm assumes:

A Multilayer adsorption with uniform enthalpy

B Monolayer adsorption with constant enthalpy of adsorption

C Linear variation of adsorption with pressure

D Exponential increase in adsorption capacity with pressure

Correct Answer: B. Monolayer adsorption with constant enthalpy of adsorption

EXPLANATION

The Langmuir model assumes monolayer adsorption on homogeneous surfaces with constant heat of adsorption, leading to saturation at high pressures.

Test

Q.13 Hard Mass Transfer

The asymptotic solutions for mass transfer in turbulent flow predict that the Sherwood number varies with Reynolds number as:

A Sh ∝ Re^0.5

B Sh ∝ Re^0.8·Sc^0.33

C Sh ∝ Re^1.0

D Sh ∝ Re^0.25·Sc^0.25

Correct Answer: B. Sh ∝ Re^0.8·Sc^0.33

EXPLANATION

For turbulent flow, empirical correlations show Sh ∝ Re^0.8·Sc^0.33 (or 0.5 depending on flow regime), derived from boundary layer theory and mass transfer analogies.

Test

Q.14 Hard Mass Transfer

For a non-isothermal diffusion process with coupled heat and mass transfer, the Lewis number Le is defined as:

A Ratio of thermal diffusivity to mass diffusivity

B Product of Schmidt and Prandtl numbers

C Ratio of heat capacity to molar volume

D Product of Grashof and Rayleigh numbers

Correct Answer: A. Ratio of thermal diffusivity to mass diffusivity

EXPLANATION

Lewis number Le = α/D_AB, where α is thermal diffusivity. It indicates the relative importance of heat and mass transfer in coupled processes. Le ≈ Sc/Pr for most gases.

Test

Q.15 Hard Mass Transfer

In foam fractionation for protein separation, the enrichment factor depends on:

A Interfacial tension and protein hydrophobicity

B Foam drainage rate only

C pH and temperature exclusively

D Column diameter only

Correct Answer: A. Interfacial tension and protein hydrophobicity

EXPLANATION

Foam fractionation enrichment factor depends on surface activity (interfacial tension), protein hydrophobicity, and preferential adsorption of proteins at gas-liquid interfaces.

Test

Q.16 Hard Mass Transfer

In coal gasification combustion analysis (2024-25 focus), the mass transfer of oxygen to solid particles is characterized by:

A External film resistance and particle surface reaction kinetics

B Only diffusion through ash layer

C Pressure variations alone

D Temperature-independent process

Correct Answer: A. External film resistance and particle surface reaction kinetics

EXPLANATION

Shrinking core model applies: external diffusion, ash diffusion, and chemical reaction all contribute. Modern focus on clean energy requires optimized design.

Test

Q.17 Hard Mass Transfer

For a reverse osmosis process, the concentration polarization effect results in:

A Higher salt concentration at membrane surface than in bulk solution

B Lower salt concentration at membrane surface

C No change in concentration profile

D Uniform concentration throughout the module

Correct Answer: A. Higher salt concentration at membrane surface than in bulk solution

EXPLANATION

Due to higher solute rejection, solutes accumulate near membrane surface, increasing local osmotic pressure and reducing driving force.

Test

Q.18 Hard Mass Transfer

The Thiele modulus (Φ) for a catalyst pellet determines whether the reaction is:

A Diffusion-limited (high Φ) or kinetically-limited (low Φ)

B Always limited by surface area

C Independent of pellet size

D Dependent only on reaction rate constant

Correct Answer: A. Diffusion-limited (high Φ) or kinetically-limited (low Φ)

EXPLANATION

Φ = L√(k/D). When Φ >> 1, diffusion controls; when Φ << 1, kinetics controls. Critical for reactor design optimization.

Test

Q.19 Hard Mass Transfer

For a pseudosteady-state diffusion with heterogeneous reaction, the effectiveness factor η accounts for:

A The reduction in reaction rate due to limited diffusion to active sites

B The increase in reaction rate due to surface effects

C The ratio of actual conversion to theoretical conversion

D The pressure drop in the catalyst bed

Correct Answer: A. The reduction in reaction rate due to limited diffusion to active sites

EXPLANATION

η = (actual reaction rate)/(rate if all surface at bulk concentration). Important in catalytic reactors where diffusion and reaction compete.

Test

Q.20 Hard Mass Transfer

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

A j_D = j_H = f/2, where j represents the Colburn factor

B All three j factors are always equal

C j_D depends on Le while j_H depends on Pr

D They are unrelated for engineering purposes

Correct Answer: A. j_D = j_H = f/2, where j represents the Colburn factor

EXPLANATION

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.

Test

1 2 3 4

All Subjects & Topics

Govt. Exams

Entrance Exams

Teacher Exams

Subjects

Quick Links

Chemical Engineering Mass Transfer

Chemical Engineering
Mass Transfer