Exothermic reaction has ΔH:
- Positive
- Zero
- Negative
- Infinite
Show answer and explanation
Answer: C. Negative
Exothermic reactions release heat to surroundings, so enthalpy of the system decreases, making ΔH negative.
FSC Chemistry: Thermochemistry, questions with answers
Practise 17 real Federal Board questions on Thermochemistry from 2023 to 2026. See the answer and explanation as soon as you answer.
17real questions
7multiple choice
5exam sessions
About Thermochemistry in FSC Chemistry
Thermochemistry is one of the 19 main chapters in our Federal Board FSC Chemistry question bank (11th class), and about 3% of its real questions come from it. Tayyari Karo has 17 real questions on this chapter from 2023 to 2026; 7 are multiple choice and marked instantly, and the rest are short and long questions with a model answer. By difficulty: 10 medium, 4 easy, 3 hard.
Work through the questions below, then open the explanation for each one. Redo the ones you missed a few days later.
Try 8 real questions
These are real past-paper questions. Think of your answer first, then open the explanation.
What will be the enthalpy of solution of NaCl if ΔH (reverse lattice) is +786 kj/mol and ΔH (hyd) is -783 kj/mol?
- +3 kj/mol
- −3 kj/mol
- +1569 kj/mol
- −1569 kj/mol
Show answer and explanation
Answer: A. +3 kj/mol
ΔH(solution) = ΔH(reverse lattice) + ΔH(hydration) = 786 + (−783) = +3 kJ/mol.
The enthalpy change when 1 mole of a substance is completely burned in oxygen is called:
- Heat of formation
- Heat of combustion
- Heat of atomization
- Heat of neutralization
Show answer and explanation
Answer: B. Heat of combustion
Complete combustion of 1 mole of substance in oxygen defines the heat (enthalpy) of combustion.
Which substance has zero value for their standard enthalpy of formation?
- H₂O
- CO₂
- Fe₂O₃
- O₃
Show answer and explanation
Answer: D. O₃
By convention, the standard enthalpy of formation of an element in its elemental/free form is taken as zero; of the choices, O₃ (an elemental form of oxygen) is keyed as zero, while H₂O, CO₂ and Fe₂O₃ are all compounds with nonzero (negative) heats of formation.
Which of the following processes is NOT endothermic?
- Vaporization
- Condensation
- Fusion
- Sublimation
Show answer and explanation
Answer: B. Condensation
Condensation (gas → liquid) releases heat, so it is exothermic; vaporization, fusion and sublimation all absorb heat.
Which of the following is NOT a state function?
- Work
- Temperature
- Pressure
- Volume
Show answer and explanation
Answer: A. Work
Work is path-dependent, not a state function; temperature, pressure and volume all depend only on the current state.
Calculate ΔH° of the reaction from the following data: S(s)+O₂(g)→SO₂(g), S(s)+3/2O₂(g)→SO₃(g) ΔH°=−395.2kJ, 2SO₂(g)+O₂(g)→2SO₃(g) ΔH°=−198.2kJ
Show model answer
Target: S + O₂ → SO₂, ΔH° = ?
Given: (1) S + 3/2O₂ → SO₃, ΔH₁° = −395.2 kJ
(2) 2SO₂ + O₂ → 2SO₃, ΔH₂° = −198.2 kJ, so SO₂+½O₂→SO₃ has ΔH = −99.1 kJ (reverse: SO₃→SO₂+½O₂, ΔH=+99.1kJ)
Target = (1) + reverse of (SO₃→SO₂+½O₂): S+3/2O₂→SO₃ (−395.2) then SO₃→SO₂+½O₂ (+99.1)
ΔH° = −395.2 + 99.1 = −296.1 kJ/mol
Why heat of vaporization (ΔHᵥ) is always greater than heat of fusion (ΔHf) for a substance?
Show model answer
Fusion (melting) only needs enough energy to break the rigid, ordered lattice into a liquid, where molecules still remain close together with most intermolecular attractions intact. Vaporization requires the molecules to be completely separated from each other, from close-packed liquid to widely-spaced gas — overcoming nearly all remaining intermolecular forces of attraction. Since this needs much more energy input, ΔHᵥ is always greater than ΔHf for the same substance.
Sessions with Thermochemistry questions
| Session | Questions |
|---|---|
| 2026 Annual | 3 |
| 2025 1st Annual | 2 |
| 2025 2nd Annual | 4 |
| 2024 Annual | 5 |
| 2023 Annual | 3 |
Common questions
What does the Thermochemistry chapter cover on this page?
17 real Federal Board (FBISE) Chemistry questions on Thermochemistry from 2023 to 2026, for 11th class. Each one shows the session it came from.
Are the answers official?
No. We could not find an official FBISE marking scheme for these papers, so the answers and explanations are written by Tayyari Karo for practice. Check anything important with your teacher or textbook.
Is it free?
You can start free with no signup. A small set of papers per subject is free, and Premium unlocks the full question bank.
Other Chemistry chapters
- Basic Concepts 53
- Fundamental Principles of Organic Chemistry 53
- s and p Block elements 37
- Chemical Equilibrium 36
- Chemical Bonding 26
- Hydrocarbons 25
- Atomic Structure 22
- Alcohols/Phenols/Ethers 22
- Transition elements 21
- Macromolecules/Biochemistry 19
- Gases 18
- Liquids 18
- Carbonyl compounds 18
- Alkyl Halides 18
- Carboxylic acids 17
- Reaction Kinetics 16
- Environmental Chemistry 16
- s-Block/Group IV-A elements 15