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FE · 8% of the exam

Thermodynamics practice questions

10 free Thermodynamics questions for the FE Chemical Exam (FE) exam, each with the correct answer and an explanation for every option.

Start the questionsFree 10-question FE quiz

What this domain covers

Thermodynamic properties and laws, phase and chemical equilibrium, and cycles for ideal and real systems.

Exam weight
8%
On a real exam
≈ 9 questions
In our bank
48 questions

Topics that come up most

  • Steam tables, property charts and equations of state
  • First and second laws, enthalpy and entropy
  • Vapour-liquid equilibrium, Raoult's and Henry's laws
  • Fugacity, activity coefficients and free energy
  • Chemical equilibrium constants and heats of reaction

How to study it

Get fluent with the steam tables, including interpolation and quality in the two-phase region; a lot of time is lost on lookups rather than on the theory.

Sample Thermodynamics questions

Try each one before opening the answer. Original questions written to the official exam objectives.

  1. Question 1

    With ΔHf°(CO) = −110.5 and ΔHf°(CO₂) = −393.5 kJ/mol, the standard heat of reaction for CO + ½O₂ → CO₂ is:

    • A−110.5 kJ/mol
    • B−504.0 kJ/mol
    • C−393.5 kJ/mol
    • D−283.0 kJ/mol
    Show answer and explanation

    Answer: D) −283.0 kJ/mol

    • AIncorrect. Use products minus reactants.
    • BIncorrect. Subtract the reactants' heats of formation.
    • CIncorrect. Subtract ΔHf° of CO.
    • DCorrect. Products minus reactants: −393.5 − (−110.5).

  2. Question 2

    2 kg of air (c_v = 0.718 kJ/(kg·K)) in a rigid tank is heated by 50 K. The heat added is:

    • A7.18 kJ
    • B100.5 kJ, using c_p
    • C35.9 kJ, using 1 kg
    • D71.8 kJ
    Show answer and explanation

    Answer: D) 71.8 kJ

    • AIncorrect. That's off by a factor of 10.
    • BIncorrect. At constant volume, use c_v.
    • CIncorrect. There are 2 kg.
    • DCorrect. \(mc_v\Delta T\).

  3. Question 3

    Taking air's molar mass as 29 kg/kmol, its density at 101.3 kPa and 300 K is about:

    • A1.18 kg/m³
    • B0.85 kg/m³
    • C11.8 kg/m³
    • D29 kg/m³
    Show answer and explanation

    Answer: A) 1.18 kg/m³

    • ACorrect. ρ = PM/RT = 101.3(29)/(8.314 × 300).
    • BIncorrect. That's inverted.
    • CIncorrect. Recheck the decimal place.
    • DIncorrect. Use ρ = PM/RT.

  4. Question 4

    For a component in an ideal-gas mixture, the fugacity equals its:

    • AMole fraction
    • BPartial pressure
    • CVapor pressure
    • DTotal pressure, always
    Show answer and explanation

    Answer: B) Partial pressure

    • AIncorrect. Multiply by total pressure.
    • BCorrect. The fugacity coefficient is 1.
    • CIncorrect. It equals partial pressure.
    • DIncorrect. It equals partial pressure.

  5. Question 5

    At the critical point of a pure substance, the latent heat of vaporization is:

    • AZero
    • BAt its maximum
    • CEqual to cp
    • DNegative
    Show answer and explanation

    Answer: A) Zero

    • ACorrect. Liquid and vapor become indistinguishable.
    • BIncorrect. It falls to zero.
    • CIncorrect. It's zero.
    • DIncorrect. It's zero.

  6. Question 6

    A real gas with a positive Joule–Thomson coefficient, passing through a throttling valve:

    • AStays at the same temperature
    • BHeats
    • CCools
    • DFreezes instantly
    Show answer and explanation

    Answer: C) Cools

    • AIncorrect. That's an ideal gas.
    • BIncorrect. That's a negative coefficient.
    • CCorrect. μ_JT = (∂T/∂P)_h > 0, and pressure falls.
    • DIncorrect. That isn't implied.

  7. Question 7

    Air (21 mol% O₂) is at a total pressure of 100 kPa. The partial pressure of oxygen is:

    • A21 kPa
    • B79 kPa
    • C100 kPa
    • D4.8 kPa
    Show answer and explanation

    Answer: A) 21 kPa

    • ACorrect. Dalton's law: \(p_i = y_i P\).
    • BIncorrect. That's nitrogen and other gases.
    • CIncorrect. Multiply by the mole fraction.
    • DIncorrect. Multiply, don't divide.

  8. Question 8

    The Clausius statement of the second law says that heat cannot spontaneously flow:

    • AFrom a colder body to a hotter body
    • BFrom a hotter body to a colder body
    • CThrough a metal wall
    • DWithout changing phase
    Show answer and explanation

    Answer: A) From a colder body to a hotter body

    • ACorrect. Doing so requires work input, as in a refrigerator.
    • BIncorrect. That happens naturally.
    • CIncorrect. Conduction through metals is common.
    • DIncorrect. Phase change isn't required.

  9. Question 9

    The specific internal energy of an ideal gas depends only on its:

    • APressure
    • BTemperature
    • CVolume
    • DContainer shape
    Show answer and explanation

    Answer: B) Temperature

    • AIncorrect. It depends only on temperature.
    • BCorrect. So does its enthalpy.
    • CIncorrect. It depends only on temperature.
    • DIncorrect. It depends only on temperature.

  10. Question 10

    For a closed system at constant pressure with only boundary work, the heat transferred equals the change in:

    • AEntropy
    • BInternal energy
    • CEnthalpy
    • DKinetic energy
    Show answer and explanation

    Answer: C) Enthalpy

    • AIncorrect. Heat isn't equal to an entropy change.
    • BIncorrect. That holds at constant volume.
    • CCorrect. Q = ΔU + PΔV = ΔH at constant pressure.
    • DIncorrect. That isn't the first-law result.

Thermodynamics: FAQs

How much of the FE exam is Thermodynamics?

Thermodynamics is 8% of the FE exam by the official exam guide's weighting, which on a 110-question form works out to roughly 9 questions. The real exam's exact split varies by form.

What does the Thermodynamics domain cover?

Thermodynamic properties and laws, phase and chemical equilibrium, and cycles for ideal and real systems.

How should I study Thermodynamics for FE?

Get fluent with the steam tables, including interpolation and quality in the two-phase region; a lot of time is lost on lookups rather than on the theory.

Where can I practise more Thermodynamics questions?

This page has 10 free Thermodynamics questions with answers. The ExamWize FE question bank has 48 questions in this domain. Every practice exam result breaks your score down by domain, and Review Mode re-drills the questions you missed.

Other FE topics

Also: 15 free questions across all topics, the FE cheat sheet and the study guide.

Get Thermodynamics exam-ready

The full FE bank has 48 Thermodynamics questions. Timed practice exams match the real exam's length and domain weights, every result shows your score per domain, and Review Mode re-drills the questions you missed.

See the full FE practice examsTake the free diagnostic

Not affiliated with NCEES; questions are original, written from the official exam outline, and never copied from the real exam.