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

The correct answer is A: Solubility of gas in liquid at equilibrium. Henry's Law constant (P = H*x) represents the equilibrium partial pressure of a gas over a solution, indicating gas solubility in the liquid.

A process where temperature and pressure both increase is most likely:

The correct answer is A: Polytropic compression (n between 1 and γ). In polytropic compression with n between 1 and γ, both T and P increase as volume decreases. Isentropic expansion decreases T and P. Throttling and isothermal keep T constant.

The Grashof number (Gr) is used to characterize natural convection. For natural convection heat transfer, which of the following correctly describes the Grashof number?

The correct answer is A: Gr = (ρ²gβΔT L³)/(μ²) - ratio of buoyancy forces to viscous forces. The Grashof number Gr = (ρ²gβΔT L³)/(μ²) represents the ratio of buoyancy forces to viscous forces in natural convection. It determines the onset of natural convection and its intensity.

Which dimensionless number represents the ratio of buoyancy forces to viscous forces in natural convection?

The correct answer is A: Grashof number (Gr). Grashof number (Gr = gβΔT L³/ν²) represents the ratio of buoyancy to viscous forces. Ra = Gr × Pr combines both effects.

In a pitot tube application, the stagnation point pressure exceeds static pressure by an amount equal to:

The correct answer is B: Dynamic pressure (½ρV²). From Bernoulli's equation: P_stagnation - P_static = ½ρV². This dynamic pressure difference is measured by pitot tubes to determine local flow velocity.

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Chemical Engineering
Thermodynamics

Process design, thermodynamics, reactions

49 Q 5 Topics Take Mock Test

Difficulty: All Easy Medium Hard 1–10 of 49

Topics in Chemical Engineering

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

Q.1 Medium Thermodynamics

A reversible process between two states A and B will have entropy change:

A Greater than that of an irreversible process between same states

B Less than that of an irreversible process between same states

C Equal to that of any path between same states

D Dependent on the type of process

Correct Answer: C. Equal to that of any path between same states

EXPLANATION

Entropy is a state function. ΔS is path-independent and same for all processes (reversible or irreversible) between fixed states.

Test

Q.2 Medium Thermodynamics

For a constant pressure process, the heat absorbed equals:

A Change in internal energy

B Change in enthalpy

C Change in entropy

D Work done by system

Correct Answer: B. Change in enthalpy

EXPLANATION

At constant pressure: ΔH = Q_p (definition of enthalpy). From ΔU = Q - W and W = PΔV, we get Q = ΔH.

Test

Q.3 Medium Thermodynamics

The compressibility factor Z for a real gas at high pressures is typically:

A Greater than 1 (repulsive forces dominate)

B Less than 1 (attractive forces dominate)

C Equal to 1

D Always greater than 2

Correct Answer: A. Greater than 1 (repulsive forces dominate)

EXPLANATION

At high pressures, molecular volume effect (b term) dominates, making Z > 1. At moderate pressures, Z < 1 due to intermolecular attractions.

Test

Q.4 Medium Thermodynamics

For a binary ideal solution, Raoult's law states that:

A Partial pressure of each component = mole fraction × vapor pressure of pure component

B Total pressure = sum of mole fractions × atmospheric pressure

C Activity coefficient of each component = 1

D Vapor pressure is independent of composition

Correct Answer: A. Partial pressure of each component = mole fraction × vapor pressure of pure component

EXPLANATION

Raoult's law: P_i = x_i × P_i° for ideal solutions. Both statements A and C are equivalent for ideal solutions.

Test

Q.5 Medium Thermodynamics

The Joule-Thomson coefficient μ_JT is negative for most gases at room temperature. This means:

A Temperature increases during expansion

B Temperature decreases during expansion

C No temperature change occurs

D Entropy decreases during expansion

Correct Answer: A. Temperature increases during expansion

EXPLANATION

μ_JT = (∂T/∂P)_H. Negative coefficient means T increases with pressure drop (cooling requires very low T or high P).

Test

Q.6 Medium Thermodynamics

In an adiabatic compression process for an ideal gas, which statement is correct?

A Temperature remains constant

B Work done equals change in internal energy

C Entropy increases

D Heat capacity is zero

Correct Answer: B. Work done equals change in internal energy

EXPLANATION

For adiabatic process, Q = 0, so ΔU = W (first law). Temperature increases during compression.

Test

Q.7 Medium Thermodynamics

The Maxwell relation derived from dG = -SdT + VdP is:

A (∂S/∂P)_T = (∂V/∂T)_P

B (∂S/∂P)_T = -(∂V/∂T)_P

C (∂S/∂T)_P = (∂V/∂P)_T

D (∂V/∂T)_P = (∂P/∂S)_V

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

EXPLANATION

From dG = -SdT + VdP, cross derivatives give (∂S/∂P)_T = -(∂V/∂T)_P, a Maxwell relation.

Test

Q.8 Medium Thermodynamics

For a spontaneous adiabatic process in an isolated system, entropy must:

A Decrease

B Remain constant

C Increase or remain constant

D Equal zero

Correct Answer: C. Increase or remain constant

EXPLANATION

Second law: dS_universe ≥ 0. For isolated systems, dS_system ≥ 0. Equality holds for reversible adiabatic processes.

Test

Q.9 Medium Thermodynamics

In a throttling process (Joule-Thomson expansion), which property remains constant?

A Temperature

B Enthalpy

C Entropy

D Internal energy

Correct Answer: B. Enthalpy

EXPLANATION

Throttling through a valve occurs at constant enthalpy (isenthalpic process). This explains cooling of real gases during expansion.

Test

Q.10 Medium Thermodynamics

The work done by a system during expansion against constant external pressure P_ext is:

A W = nRT ln(V_f/V_i)

B W = P_ext(V_f - V_i)

C W = ∫P_int dV

D W = ΔH - TΔS

Correct Answer: B. W = P_ext(V_f - V_i)

EXPLANATION

For constant external pressure, work is W = P_ext × ΔV. This is path-dependent work for irreversible processes.

Test

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