A flat-plate solar collector has a black absorber plate maintained at 80°C. The ambient temperature is 20°C and the heat loss coefficient (overall U value including radiation and convection) is 8 W/(m²·K). For a collector area of 4 m², what is the he

The correct answer is C: 1920 W. Q_loss = U × A × ΔT = 8 × 4 × (80-20) = 8 × 4 × 60 = 1920 W. The overall U value already accounts for both convective and radiative losses.

The mean free path (λ) in gas kinetic theory at standard conditions is approximately 60 nm. This implies that at atmospheric pressure, heat conduction in gases is primarily through:

The correct answer is A: Molecular diffusion. Small mean free path (60 nm

The Peclet number (Pe = Re·Pr) is used to determine the relative importance of convection to conduction. For Pe

The correct answer is B: Conduction is dominant. The Peclet number Pe = Re·Pr = (velocity × characteristic length × ρ·cp)/k represents the ratio of convection to conduction. When Pe

Which of the following statements about laminar flow in a circular pipe is correct?

The correct answer is B: Velocity profile is parabolic and maximum velocity occurs at the center. In laminar flow through circular pipes, the velocity distribution follows Hagen-Poiseuille flow with parabolic profile. Maximum velocity is at the centerline (V_max = 2×V_avg), and velocity is zero at the wall (no-slip condition).

In unsteady-state conduction with Bi

The correct answer is A: Lumped capacitance method - uniform internal temperature. When Bi < 0.1, convective resistance is much larger than conductive resistance, allowing assumption of uniform temperature throughout the object.

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Chemical Engineering
Chemical Reaction Engineering

Process design, thermodynamics, reactions

26 Q 5 Topics Take Mock Test

Difficulty: All Easy Medium Hard 21–26 of 26

Topics in Chemical Engineering

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

Q.21 Hard Chemical Reaction Engineering

In desorption-limited catalytic reactions, which step determines the overall reaction rate?

A Reactant adsorption on catalyst surface

B Surface reaction between adsorbed species

C Product desorption from catalyst surface

D Diffusion of reactant to catalyst surface

Correct Answer: C. Product desorption from catalyst surface

EXPLANATION

When desorption is the rate-limiting step, products stick to the catalyst and their slow removal prevents further reaction cycles, controlling overall rate

Test

Q.22 Hard Chemical Reaction Engineering

For consecutive reactions A→B→C, the concentration of intermediate B is maximum at time t_max. This time depends on:

A Only k₁ and k₂

B Only initial concentration of A

C Both k₁, k₂ and initial concentration of A

D Temperature only

Correct Answer: A. Only k₁ and k₂

EXPLANATION

t_max = ln(k₂/k₁)/(k₂-k₁), depends only on rate constants, independent of [A]₀

Test

Q.23 Hard Chemical Reaction Engineering

Which approximation is used in steady-state kinetics for enzyme reactions?

A Quasi-equilibrium approximation

B Steady-state approximation for ES complex

C Pre-equilibrium approximation

D Both B and C

Correct Answer: D. Both B and C

EXPLANATION

Both steady-state (d[ES]/dt = 0) and pre-equilibrium approximations are used in Michaelis-Menten derivation

Test

Q.24 Hard Chemical Reaction Engineering

For a reaction with E_a = 50 kJ/mol, if temperature is increased from 300K to 400K, by what factor does rate constant increase? (R = 8.314 J/mol·K)

A 3.2 times

B 8.5 times

C 15.8 times

D 22.3 times

Correct Answer: C. 15.8 times

EXPLANATION

ln(k₂/k₁) = (50000/8.314)[1/300 - 1/400] = 2.76; k₂/k₁ = e^2.76 ≈ 15.8

Test

Q.25 Hard Chemical Reaction Engineering

Which reactor configuration gives maximum yield for a series reaction A→B→C where k₁ >> k₂?

A Batch reactor with optimized residence time

B CSTR operating at high temperature

C PFR with very high conversion

D Recycle reactor

Correct Answer: A. Batch reactor with optimized residence time

EXPLANATION

For A→B→C series, batch allows control of residence time to maximize intermediate B before it converts to C

Test

Q.26 Hard Chemical Reaction Engineering

What is the activation energy for a reaction if its rate constant doubles when temperature increases from 300K to 310K?

A 45.6 kJ/mol

B 52.8 kJ/mol

C 60.2 kJ/mol

D 72.5 kJ/mol

Correct Answer: B. 52.8 kJ/mol

EXPLANATION

Using Arrhenius equation: ln(k₂/k₁) = (Eₐ/R)[1/T₁ - 1/T₂]; ln(2) = (Eₐ/8.314)[1/300 - 1/310]; Eₐ ≈ 52.8 kJ/mol

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