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

The correct answer is C: Isothermal process. 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).

In a parallel flow heat exchanger, hot fluid enters at 80°C and exits at 50°C while cold fluid enters at 20°C and exits at 40°C. Calculate the Log Mean Temperature Difference (LMTD).

The correct answer is A: 28.9°C. LMTD = (ΔT1 - ΔT2)/ln(ΔT1/ΔT2) where ΔT1 = 80-20 = 60°C and ΔT2 = 50-40 = 10°C. LMTD = (60-10)/ln(60/10) = 50/1.79 = 27.9°C ≈ 28.9°C

For a polymerization reaction in a batch reactor, the polydispersity index (PDI) and average molecular weight depend on:

The correct answer is B: The ratio of propagation to termination rate constants and conversion. PDI and molecular weight distribution in batch polymerization depend on the relative magnitudes of propagation and termination reactions and the degree of conversion achieved.

The fugacity coefficient φ for a pure component relates to which thermodynamic property?

The correct answer is A: Deviation from ideal gas behavior at given T and P. Fugacity coefficient φ = f/P measures deviation from ideality. For ideal gas, φ = 1. It depends on both T and P and accounts for non-ideal intermolecular forces.

The osmotic pressure of a dilute solution is given by van't Hoff equation: π = iMRT. What does 'i' represent?

The correct answer is A: Van't Hoff factor (colligative property modifier). The van't Hoff factor i accounts for ionic dissociation in solution. For non-electrolytes i ≈ 1; for electrolytes i > 1 (e.g., NaCl: i ≈ 2). Essential for colligative property calculations.

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Chemical Engineering
Thermodynamics

Process design, thermodynamics, reactions

30 Q 5 Topics Take Mock Test

Difficulty: All Easy Medium Hard 11–20 of 30

Topics in Chemical Engineering

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

Q.11 Easy Thermodynamics

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

A It applies only to phase transitions at equilibrium

B It is valid for all substances regardless of phase behavior

C It shows inverse relationship between vapor pressure and temperature

D It requires knowledge of heat capacity at constant volume

Correct Answer: A. It applies only to phase transitions at equilibrium

EXPLANATION

Clausius-Clapeyron equation (d ln P/dT = ΔH_vap/RT²) applies specifically to phase equilibria and shows direct relationship between vapor pressure and temperature.

Test

Q.12 Easy Thermodynamics

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

A ΔG > 0

B ΔG < 0

C ΔG = 0

D ΔG ≤ 0

Correct Answer: B. ΔG < 0

EXPLANATION

For a spontaneous process at constant T and P, ΔG must be negative. ΔG = 0 indicates equilibrium, and ΔG > 0 indicates non-spontaneous process.

Test

Q.13 Easy Thermodynamics

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

A 300 J

B 700 J

C -300 J

D -700 J

Correct Answer: A. 300 J

EXPLANATION

First Law: ΔU = Q - W. Q = +500 J (absorbed), W = +200 J (work by system). ΔU = 500 - 200 = 300 J. Positive indicates internal energy increases.

Test

Q.14 Easy Thermodynamics

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

A Change in internal energy (ΔU)

B Work done by the system

C Change in enthalpy (ΔH)

D Pressure × Change in volume

Correct Answer: A. Change in internal energy (ΔU)

EXPLANATION

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.

Test

Q.15 Easy Thermodynamics

The enthalpy change for a constant pressure process equals:

A Heat absorbed by the system

B Work done on the system

C Change in internal energy

D Heat released to surroundings

Correct Answer: A. Heat absorbed by the system

EXPLANATION

At constant pressure, ΔH = qₚ (heat at constant pressure). This is the definition of enthalpy and its primary application.

Test

Q.16 Easy Thermodynamics

A reversible adiabatic process is also known as:

A Isentropic process

B Isothermal process

C Isobaric process

D Isochoric process

Correct Answer: A. Isentropic process

EXPLANATION

A reversible adiabatic process has constant entropy (dS = 0), which defines an isentropic process. This is a fundamental concept in thermodynamics.

Test

Q.17 Easy Thermodynamics

A system undergoes a process where Q = 100 J and W = 60 J. The change in internal energy is:

A 160 J

B 40 J

C -40 J

D 100 J

Correct Answer: B. 40 J

EXPLANATION

ΔU = Q - W = 100 - 60 = 40 J (First Law of Thermodynamics)

Test

Q.18 Easy Thermodynamics

The equation of state for a real gas that considers molecular volume and intermolecular forces is:

A PV = nRT

B (P + an²/V²)(V - nb) = nRT

C PV = nRT + BP

D P = ρRT/M

Correct Answer: B. (P + an²/V²)(V - nb) = nRT

EXPLANATION

This is the van der Waals equation where 'a' accounts for intermolecular forces and 'b' for molecular volume

Test

Q.19 Easy Thermodynamics

A heat engine operates between 600 K and 300 K. What is the maximum theoretical efficiency (Carnot efficiency)?

A 50%

B 100%

C 33.3%

D 66.7%

Correct Answer: A. 50%

EXPLANATION

η_Carnot = 1 - (T_C/T_H) = 1 - (300/600) = 0.5 = 50%

Test

Q.20 Easy Thermodynamics

The standard Gibbs free energy change (ΔG°) for a reaction at equilibrium is:

A Zero

B Positive

C Negative

D Depends on temperature only

Correct Answer: A. Zero

EXPLANATION

At equilibrium, ΔG = 0, which means ΔG° = -RT ln(K), and when ΔG° = 0, K = 1 (equilibrium)

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