Chapter 43 · 873 practice MCQs
MDCAT Thermodynamics MCQs 2026 | First Law, Cp − Cv = R
Heat is not a state function. Internal energy is. Unit 7 is the first law, , Cp − , and heat flowing hot to cold — plus the indicator diagram that is just a rectangle of work.
·6 min read·Usman Ubaid
What MDCAT 2026 asks in Unit 43 Thermodynamics
PMDC Unit 7 is the first law with MDCAT’s sign convention stated on the question. Learn the processes by what is zero: isochoric (all Q becomes ); isothermal ideal gas = 0 (all Q becomes W); adiabatic = W). Isobaric work is the P rectangle.
Mayer’s relation Cp − is the molar-heat item. Cp > Cv because expansion work is extra heat at constant pressure. Thermal equilibrium is one temperature, not one internal energy. Heat still flows hot to cold.
Twenty conceptual MCQs with indicator diagrams you can read after you lock.
- = Q + W with the sign convention the stem states. Do not mix textbooks.
- for isobaric expansion (the rectangle).
- Isochoric: Isothermal ideal: = 0. Adiabatic: , T still changes.
- Cp − Cp > Cv always for an ideal gas.
- for a temperature change of a solid or liquid. Heat is not U.
Often-asked Thermodynamics MCQ patterns
These are the Thermodynamics ideas that keep coming every year with new numbers.
- Using on an isochoric process ( = 0, so
- Saying temperature is internal energy. U for an ideal gas tracks T, but they are not the same word.
- Forgetting that adiabatic still changes T.
- Heat flowing cold to hot ‘in a fridge’ without naming the work input.
Worked Thermodynamics numericals (
Work these on paper first. Then open the Unit 43 quiz — the same numbers are in the questions, with wrong options built from the usual mix-ups.
An ideal gas in a rigid box is given of heat. Work and ?
- = Q + J (if W is work on the gas) — follow the stem’s signs.
- The whole becomes internal energy; T rises.
= Q. No rectangle on the P–V diagram: a vertical line.
J/mol·K for an ideal gas. Cp?
- Cp − ≈ /mol· ≈ /mol·K.
- Cp is larger. Equal would deny expansion work.
+ R. The extra is the isobaric expansion work per mole per kelvin.
Thermodynamics traps that steal the mark
A good option is a true sentence about the wrong quantity. If you miss, the quiz names the mix-up on the option you actually picked.
- Using on an isochoric process.
- Saying temperature is internal energy.
- Forgetting that adiabatic still changes T.
- Treating heat as a state function stored ‘inside’ the gas.
- Reading work as the area under a P–T graph.
Thermodynamics formula sheet for MDCAT 2026
Write these until they are cheaper than thinking. Then open the Thermodynamics quiz and make the picture agree.
How to practise Unit 43 Thermodynamics MCQs
Before numbers, name the process in one word: isochoric, isobaric, isothermal, adiabatic. Then write the zero. Then apply the first law.
On indicator diagrams, work is the area under P–V, not P–T. Shade it in your head before you pick.
g is not needed here. Mechanics used this unit’s knobs are Q, W and T.
Choose topics and a test length up to 180 from the 873-question bank. Tutor Mode explains each selection; Timed Exam reveals explanations on submission. Use the complete review to revise mistakes and download your results.
FAQ
Common questions
Is g needed in thermodynamics?
Not in these questions. Mechanics used here the knobs are Q, W and T.
Why is Cp greater than Cv?
At constant pressure the gas expands and does work, so more heat is needed for the same . Mayer: Cp − For one mole of an ideal gas, Cp − At constant volume no expansion work is done, while at constant pressure part of the supplied heat goes into work against the surroundings.
Does an adiabatic process keep temperature constant?
No. That is isothermal. Adiabatic means an ideal gas still changes T when it expands or is compressed. Apply the first law with a consistent work sign convention. An ideal gas cools during adiabatic expansion and warms during compression; no heat exchange does not mean no energy transfer by work.
What is isochoric work?
Zero. Volume does not change, so P is zero. All heat goes into . In a pressure–volume diagram a constant-volume process is a vertical line, with zero area under it. For an ideal gas, adding heat then increases internal energy and temperature.
How many Thermodynamics MCQs are available on DIFF. MDCAT?
The current Thermodynamics question bank contains 873 practice MCQs across 5 topics. This is the bank size, not the length of one test. Choose your topics and a question count from 1 to 180, limited by the questions available in those topics.
Which topics does the Thermodynamics quiz cover?
The selectable topics are Thermal Equilibrium, Specific Heat, Thermodynamic Work, First Law, Cp-Cv Relation. Use Select all for a broad chapter drill, Clear to start a focused selection, or choose individual topics. Questions are drawn from your chosen topics, so you can target a weak concept before returning to a wider test.
How do I build a custom Thermodynamics test?
Open the chapter builder, select one or more topics, enter your question count, and choose Tutor Mode or Timed Exam. The available-question total updates with your selection. Start Test generates a shuffled drill; you do not have to follow a fixed Quiz 1 or Quiz 2 sequence.
What is the difference between Tutor Mode and Timed Exam?
Tutor Mode gives feedback and an explanation after you choose an option, and you can change or clear that choice. Timed Exam runs a countdown and keeps explanations hidden until submission. Both modes let you move between questions, use the paper map, and submit for a complete review.
How do I review and download my Thermodynamics quiz?
Select Submit Quiz, then Submit & View Explanations. The review includes every question in your test, all options, your selection, the marked correct answer when a key is available, and the explanation. Download PDF saves a paginated review; Download Review saves an HTML copy you can open in a browser. The review also includes DIFF. MDCAT community links.
How should I use Thermodynamics MCQs to improve?
Start with a short tutor drill on one of these topics: Thermal Equilibrium, Specific Heat, Thermodynamic Work. Read the explanation for incorrect and uncertain answers, revise the relevant textbook section, and retry before taking a timed drill. Compare your reasoning with the answer key rather than memorising the option letter.
Ready to sit Unit 43 Thermodynamics — 873 MCQs, 873 labs?