For a reaction with activation energy E_a = 50 kJ/mol, by what factor does rate constant increase if temperature increases from 300K to 310K? (R = 8.314 J/mol·K)

The correct answer is B: 2.0. Using Arrhenius: ln(k₂/k₁) = (E_a/R)(T₂-T₁)/(T₁T₂) ≈ 1.96, so k₂/k₁ ≈ 2.0

In fluid mechanics, which dimensionless number represents the ratio of inertial forces to viscous forces?

The correct answer is A: Reynolds number. Reynolds number Re = (Inertial forces)/(Viscous forces) = ρVD/μ. It characterizes flow regime (laminar vs turbulent).

In transient heat conduction, the Fourier number (Fo = α·t/L²) represents:

The correct answer is D: Measure of penetration depth of thermal disturbance. Fourier number represents the dimensionless time or the measure of how far thermal disturbances have penetrated into the material. High Fo indicates significant internal temperature changes, while low Fo indicates the disturbance is confined to the surface.

For a sharp-edged orifice, the coefficient of contraction (Cc) typically ranges between:

The correct answer is B: 0.60-0.65. The coefficient of contraction for sharp-edged orifices is typically 0.60-0.65 due to the vena contracta effect where the jet contracts after leaving the orifice.

In a throttling process (Joule-Thomson expansion), for an ideal gas, the enthalpy change is:

The correct answer is C: Zero. For an ideal gas, h depends only on temperature. Since throttling is isenthalpic (h constant), temperature remains constant, making ΔH = 0.

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Chemical Engineering
Thermodynamics

Process design, thermodynamics, reactions

30 Q 5 Topics Take Mock Test

Difficulty: All Easy Medium Hard 21–30 of 30

Topics in Chemical Engineering

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

Q.21 Easy Thermodynamics

For a closed system at constant volume, the first law of thermodynamics simplifies to:

A ΔU = Q - W

B ΔU = Q

C ΔU = W

D ΔH = Q

Correct Answer: B. ΔU = Q

EXPLANATION

At constant volume, W = P×ΔV = 0. Therefore, ΔU = Q - 0 = Q

Test

Q.22 Easy Thermodynamics

Which of the following represents a state function?

A Work done by the system

B Heat absorbed by the system

C Internal energy of the system

D Path followed during a process

Correct Answer: C. Internal energy of the system

EXPLANATION

Internal energy (U), Enthalpy (H), Gibbs energy (G) are state functions. Work and heat are path functions

Test

Q.23 Easy Thermodynamics

The entropy change for an isothermal irreversible expansion of an ideal gas from V₁ to V₂ is:

A ΔS = nR ln(V₂/V₁)

B ΔS = nCV ln(T₂/T₁)

C ΔS = 0

D ΔS = -nR ln(V₂/V₁)

Correct Answer: A. ΔS = nR ln(V₂/V₁)

EXPLANATION

For an isothermal process of ideal gas, entropy depends only on volume ratio: ΔS = nR ln(V₂/V₁), regardless of reversibility

Test

Q.24 Easy Thermodynamics

A gas mixture contains N₂ (40% mole) and O₂ (60% mole) at 1 atm and 298 K. Calculate the partial pressure of O₂ in the mixture.

A 0.6 atm

B 0.4 atm

C 1.0 atm

D 0.8 atm

Correct Answer: A. 0.6 atm

EXPLANATION

Partial pressure = Total pressure × Mole fraction. P_O₂ = 1 atm × 0.60 = 0.6 atm (Dalton's Law)

Test

Q.25 Easy Thermodynamics

Which process is represented by a horizontal line on a T-S (Temperature-Entropy) diagram?

A Isobaric process

B Isochoric process

C Isothermal process

D Isentropic process

Correct Answer: C. Isothermal process

EXPLANATION

On a T-S diagram, horizontal line means constant temperature (T = const), which is an isothermal process. A vertical line would represent isentropic process (S = const).

Test

Q.26 Easy Thermodynamics

In a constant pressure calorimeter, 1 kg of water is heated from 25°C to 75°C. Heat absorbed is approximately (Cₚ of water = 4.18 kJ/kg·K):

A 104.5 kJ

B 209 kJ

C 418 kJ

D 836 kJ

Correct Answer: B. 209 kJ

EXPLANATION

Q = m × Cₚ × ΔT = 1 × 4.18 × (75-25) = 1 × 4.18 × 50 = 209 kJ. At constant pressure, Q = ΔH.

Test

Q.27 Easy Thermodynamics

The compressibility factor Z for an ideal gas is:

A Always greater than 1

B Always equal to 1

C Always less than 1

D Depends only on pressure

Correct Answer: B. Always equal to 1

EXPLANATION

For ideal gas, Z = PV/nRT = 1 always. For real gases, Z ≠ 1 due to intermolecular forces and molecular volume.

Test

Q.28 Easy Thermodynamics

A system absorbs 500 J of heat and does 200 J of work. The change in internal energy is:

A 300 J

B -300 J

C 700 J

D -700 J

Correct Answer: A. 300 J

EXPLANATION

Using ΔU = Q - W, where Q = +500 J (absorbed) and W = +200 J (work done by system). Therefore, ΔU = 500 - 200 = 300 J.

Test

Q.29 Easy Thermodynamics

According to the first law of thermodynamics, ΔU = Q - W. In this equation, W represents:

A Work done on the system

B Work done by the system

C Total work including heat transfer

D Work at constant pressure only

Correct Answer: B. Work done by the system

EXPLANATION

In the convention ΔU = Q - W, W is work done by the system. This is the IUPAC recommended convention used in most thermodynamics calculations.

Test

Q.30 Easy Thermodynamics

Which of the following is NOT an extensive property?

A Volume

B Temperature

C Mass

D Internal energy

Correct Answer: B. Temperature

EXPLANATION

Temperature is an intensive property as it does not depend on the quantity of substance. Volume, mass, and internal energy are extensive properties that depend on the amount of material.

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