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.

For a reversible reaction A ⇌ B with equilibrium constant Ke = 4, what is the maximum theoretical conversion in a batch reactor at equilibrium?

The correct answer is B: 80%. At equilibrium: Ke = [B]/[A] = 4. If initial [A]₀ = C, then at equilibrium: 4 = X/(1-X), solving X = 0.8 or 80%

The Clausius-Clapeyron equation relates vapor pressure to temperature. Which statement is correct?

The correct answer is A: It applies only to phase transitions at equilibrium. Clausius-Clapeyron equation (d ln P/dT = ΔH_vap/RT²) applies specifically to phase equilibria and shows direct relationship between vapor pressure and temperature.

In a constant volume process, the heat added to the system equals:

The correct answer is A: Change in internal energy (ΔU). For constant volume: W = 0, so Q = ΔU from first law (ΔU = Q - W). This is isochoric process where all heat goes to internal energy change.

The Fick's first law of diffusion in binary mixtures states that the molar flux J_A is proportional to:

The correct answer is B: Concentration gradient and bulk flow. Fick's law: J_A = -D_AB(dC_A/dz) + C_A(J_A + J_B). The total flux includes both diffusive and convective contributions due to bulk flow.

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247 Q 5 Topics Take Mock Test

Difficulty: All Easy Medium Hard 191–200 of 247

Topics in Chemical Engineering

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

Q.191 Medium Heat Transfer

In steady-state heat conduction through a composite wall with three layers in series, if the thermal conductivities are k₁ > k₂ > k₃, which layer will have the maximum temperature drop?

A Layer 1

B Layer 2

C Layer 3

D Temperature drop is equal in all layers

Correct Answer: C. Layer 3

EXPLANATION

Temperature drop across a layer is inversely proportional to thermal conductivity (ΔT ∝ 1/k). Since k₃ is smallest, layer 3 experiences maximum temperature drop.

Test

Q.192 Medium Heat Transfer

In unsteady-state conduction with Bi

A Lumped capacitance method - uniform internal temperature

B Temperature varies spatially and temporally

C Steady-state conditions apply

D Conduction resistance is infinite

Correct Answer: A. Lumped capacitance method - uniform internal temperature

EXPLANATION

When Bi < 0.1, convective resistance is much larger than conductive resistance, allowing assumption of uniform temperature throughout the object.

Test

Q.193 Medium Heat Transfer

For natural convection from a vertical isothermal plate in air, which correlation applies best?

A Nu = C × (Gr × Pr)^n, where n ≈ 0.25 for laminar

B Nu = 0.023 × Re^0.8 × Pr^0.4

C Nu = constant

D Nu = 3.66 + (other terms)

Correct Answer: A. Nu = C × (Gr × Pr)^n, where n ≈ 0.25 for laminar

EXPLANATION

For natural convection: Nu = C(Ra)^n where Ra = Gr×Pr. For laminar boundary layer (Ra < 10^9), n ≈ 0.25. For turbulent (Ra > 10^9), n ≈ 0.33.

Test

Q.194 Medium Heat Transfer

For a flat plate solar collector with selective coating, which of the following is most desirable?

A High absorptivity (α) and high emissivity (ε) in solar spectrum

B High absorptivity (α) in solar spectrum and low emissivity (ε) in IR range

C Low absorptivity (α) and low emissivity (ε)

D Equal α and ε values

Correct Answer: B. High absorptivity (α) in solar spectrum and low emissivity (ε) in IR range

EXPLANATION

Selective coatings should absorb solar radiation (high α_sol) but minimize thermal radiation losses (low ε_IR), maximizing collector efficiency.

Test

Q.195 Medium Heat Transfer

In a shell-and-tube heat exchanger (1 shell pass, 2 tube passes), the effectiveness is lower than counter-current primarily because:

A Part of the flow behaves co-currently

B Fouling resistance is higher

C Pressure drop increases

D Material properties change

Correct Answer: A. Part of the flow behaves co-currently

EXPLANATION

In 1-2 arrangement, portion of shell-side flows co-currently with tube-side, reducing overall effectiveness compared to true counter-current.

Test

Q.196 Medium Heat Transfer

For turbulent flow in smooth pipes (Pr > 0.6), which correlation is most commonly used?

A Dittus-Boelert: Nu = 0.023 Re^0.8 Pr^0.4

B Sieder-Tate: Nu = 0.027 Re^0.8 Pr^(1/3)

C Gnielinski equation

D Laminar correlation only

Correct Answer: A. Dittus-Boelert: Nu = 0.023 Re^0.8 Pr^0.4

EXPLANATION

Dittus-Boelert correlation is the most widely used for turbulent flow with Pr > 0.6. Valid for Re > 10,000, smooth pipes, and fully developed flow.

Test

Q.197 Medium Heat Transfer

The log mean temperature difference (LMTD) correction factor F is required primarily for which configuration?

A Counter-current heat exchangers

B Cross-flow and more complex arrangements

C Co-current heat exchangers

D Double-pipe heat exchangers only

Correct Answer: B. Cross-flow and more complex arrangements

EXPLANATION

F-correction factor is used for non-counter-current arrangements (cross-flow, 1-2 shell-tube, etc.) where LMTD doesn't directly apply without correction.

Test

Q.198 Medium Heat Transfer

The Number of Transfer Units (NTU) is defined as which of the following?

A UA/(ṁC_p)_min

B ΔT_LMTD/ΔT_m

C Q_actual/Q_max

D hA/C_p

Correct Answer: A. UA/(ṁC_p)_min

EXPLANATION

NTU = UA/(ṁC_p)_min is the ratio of overall heat transfer capacity to minimum heat capacity rate, used in ε-NTU method.

Test

Q.199 Medium Heat Transfer

In a counter-current heat exchanger with equal heat capacities, what is the maximum possible effectiveness?

A 100% or 1.0

B 50%

C Limited by NTU

D Cannot be determined

Correct Answer: A. 100% or 1.0

EXPLANATION

For counter-current arrangement, maximum effectiveness can approach 1.0 (100%) with infinite NTU. For co-current, it's limited to (1-exp(-NTU(1+C_r)))/(1+C_r).

Test

Q.200 Medium Heat Transfer

For fully developed laminar flow in a circular pipe with constant wall heat flux, which Nusselt number (Nu) is approximately correct?

A Nu ≈ 3.66

B Nu ≈ 4.36

C Nu ≈ 5.33

D Nu ≈ 8.24

Correct Answer: B. Nu ≈ 4.36

EXPLANATION

For constant heat flux boundary condition (H1 type) in circular pipes with fully developed laminar flow, Nu ≈ 4.36. For constant wall temperature (H2), Nu ≈ 3.66.

Test

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