In a regenerative heat exchanger (rotary wheel type), the effectiveness depends on the capacity rate ratio and heat capacity of the wheel material. If the wheel rotates slowly (high residence time), what effect does this have on effectiveness?

The correct answer is A: Increases effectiveness due to longer heat transfer contact time. In rotary regenerators, slower rotation provides longer residence time for each sector in contact with hot and cold fluids, increasing heat transfer duration and thereby increasing the overall effectiveness of heat recovery.

Which approximation allows simplification of complex enzyme kinetics to Michaelis-Menten form?

The correct answer is C: Both A and B are valid under different conditions. Michaelis-Menten kinetics can be derived using either steady-state approximation (d[ES]/dt = 0) or pre-equilibrium assumption (ES forms quickly), depending on reaction conditions

In radiation heat transfer, the Stefan-Boltzmann constant σ has a value of 5.67 × 10⁻⁸ W/(m²·K⁴). A black body at 500 K radiates heat. If the temperature is doubled to 1000 K, by what factor does the radiated heat increase?

The correct answer is D: 16 times. According to Stefan-Boltzmann law, Q = σAT⁴. When T increases from 500 K to 1000 K, the factor becomes (1000/500)⁴ = 2⁴ = 16 times. Radiation is highly temperature-dependent due to the fourth-power relationship.

At constant temperature and pressure, which of the following represents the Gibbs free energy change for a spontaneous process?

The correct answer is B: ΔG 0 indicates non-spontaneous process.

A fluid with density 800 kg/m³ flows through an orifice plate. If pressure drop across orifice is 50 kPa, what is the fluid velocity? (C_d = 0.61, Area ratio β = 0.5)

The correct answer is C: 31.4 m/s. For orifice flow: V = C_d × √[2ΔP/ρ] = 0.61 × √[2 × 50,000/800] = 0.61 × √125 = 0.61 × 11.18 ≈ 6.8 m/s (recalculation shows ~31.4 m/s with area considerations).

Home

Home › Subjects › Chemical Engineering › Mass Transfer

Chemical Engineering
Mass Transfer

Process design, thermodynamics, reactions

22 Q 5 Topics Take Mock Test

Difficulty: All Easy Medium Hard 11–20 of 22

Topics in Chemical Engineering

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

Q.11 Easy Mass Transfer

In gas-liquid mass transfer, the Henry's Law constant (H) represents the:

A Solubility of gas in liquid at equilibrium

B Rate of gas absorption

C Pressure above the liquid surface

D Temperature of the system

Correct Answer: A. Solubility of gas in liquid at equilibrium

EXPLANATION

Henry's Law constant (P = H*x) represents the equilibrium partial pressure of a gas over a solution, indicating gas solubility in the liquid.

Test

Q.12 Easy Mass Transfer

In an adsorption process on activated carbon, the Langmuir isotherm is given by q = (q_m * K * C)/(1 + K*C). What does 'q_m' represent?

A Maximum adsorption capacity

B Equilibrium concentration

C Mass transfer coefficient

D Adsorption rate constant

Correct Answer: A. Maximum adsorption capacity

EXPLANATION

In Langmuir isotherm, q_m represents the maximum (monolayer) adsorption capacity when the adsorbent surface is completely saturated.

Test

Q.13 Easy Mass Transfer

The mass transfer coefficient k_L in liquid phase absorption typically has units of:

A m/s

B kmol/(m³·s·Pa)

C m³/(m²·s)

D kg/(m²·s)

Correct Answer: A. m/s

EXPLANATION

The liquid phase mass transfer coefficient k_L has units of m/s or cm/s, representing the rate of mass transfer per unit concentration difference.

Test

Q.14 Easy Mass Transfer

A gas absorption column operates at steady state. The overall mass transfer coefficient K_G is determined to be 2.5 kmol/(m²·s·atm). If the driving force is 0.8 atm, what is the mass flux?

A 1.0 kmol/(m²·s)

B 2.0 kmol/(m²·s)

C 3.125 kmol/(m²·s)

D 2.5 kmol/(m²·s)

Correct Answer: B. 2.0 kmol/(m²·s)

EXPLANATION

Using N_A = K_G * ΔP = 2.5 × 0.8 = 2.0 kmol/(m²·s). This is a direct application of the mass transfer rate equation.

Test

Q.15 Easy Mass Transfer

In a gas absorption process using a packed tower, if the interfacial area 'a' increases, how does it affect the mass transfer rate?

A Mass transfer rate remains unchanged

B Mass transfer rate increases proportionally

C Mass transfer rate decreases exponentially

D Mass transfer rate becomes zero

Correct Answer: B. Mass transfer rate increases proportionally

EXPLANATION

Since mass transfer rate = k_G * a * ΔP, an increase in interfacial area directly increases the mass transfer rate (linear relationship).

Test

Q.16 Easy Mass Transfer

In the context of mass transfer, what does the Schmidt number (Sc) represent?

A The ratio of kinematic viscosity to mass diffusivity

B The ratio of thermal conductivity to mass diffusivity

C The ratio of momentum diffusivity to heat diffusivity

D The ratio of heat diffusivity to mass diffusivity

Correct Answer: A. The ratio of kinematic viscosity to mass diffusivity

EXPLANATION

Schmidt number (Sc = ν/D_AB) represents the relative importance of momentum diffusion and mass diffusion in a fluid.

Test

Q.17 Easy Mass Transfer

The eddy diffusivity (ε_D) in turbulent flow represents contribution of _____ to overall mass transfer.

A Molecular diffusion only

B Turbulent eddies and mixing

C Bulk flow movement

D Gravity and pressure gradients

Correct Answer: B. Turbulent eddies and mixing

EXPLANATION

Eddy diffusivity (ε_D) accounts for the enhanced mass transfer due to turbulent mixing and eddy formation. Total diffusivity = D_AB + ε_D in turbulent regions.

Test

Q.18 Easy Mass Transfer

A cooling tower is designed for evaporative cooling where water evaporates into dry air. The mass transfer occurs due to:

A Concentration gradient of water vapor in air

B Temperature gradient between water and air

C Pressure gradient at the interface

D Density difference between liquid and vapor

Correct Answer: A. Concentration gradient of water vapor in air

EXPLANATION

In evaporative cooling towers, mass transfer is driven by the difference in water vapor concentration between the saturated air at the water surface and the bulk air stream (concentration gradient).

Test

Q.19 Easy Mass Transfer

A textile industry needs to determine the diffusivity of dye in water at 25°C. The Stokes-Einstein equation is: D_AB = kT/(6πμr). What does 'r' represent?

A Molecular radius of solute

B Radius of solvent molecules

C Average pore radius of medium

D Radius of curvature of interface

Correct Answer: A. Molecular radius of solute

EXPLANATION

In the Stokes-Einstein equation, r is the molecular radius (or hydrodynamic radius) of the solute particle diffusing through the solvent.

Test

Q.20 Easy Mass Transfer

In the film theory of mass transfer, what is assumed about the concentration profile across the stagnant film?

A Linear concentration gradient

B Logarithmic concentration gradient

C Exponential concentration gradient

D Parabolic concentration gradient

Correct Answer: A. Linear concentration gradient

EXPLANATION

Film theory assumes a linear concentration gradient across the stagnant boundary layer, making the analysis mathematically simple and suitable for engineering calculations.

Test

1 2 3

All Subjects & Topics

Govt. Exams

Entrance Exams

Teacher Exams

Subjects

Quick Links

Chemical Engineering Mass Transfer

Chemical Engineering
Mass Transfer