Molar volume concept is applicable mainly to:
- Gases
- Liquids
- Solids
- Plasma
Show answer and explanation
Answer: A. Gases
Molar volume (22.4 L/mol at STP) is a defined, consistent concept for gases, since gas molecules are widely and uniformly spaced.
FSC Chemistry: Gases, questions with answers
Practise 18 real Federal Board questions on Gases from 2023 to 2026. See the answer and explanation as soon as you answer.
18real questions
7multiple choice
5exam sessions
About Gases in FSC Chemistry
Gases is one of the 19 main chapters in our Federal Board FSC Chemistry question bank (11th class), and about 4% of its real questions come from it. Tayyari Karo has 18 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: 15 medium, 2 easy, 1 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.
The number of molecules present in 67.2 dm³ of He gas at STP is:
- 6.02×10²⁴
- 1.204×10²⁴
- 1.806×10²⁴
- 2.4×10²⁴
Show answer and explanation
Answer: C. 1.806×10²⁴
Moles = 67.2/22.4 = 3 mol; molecules = 3 × 6.022×10²³ = 1.806×10²⁴.
Peroxyacetyl nitrate (PAN) is formed by the reaction of oxides of nitrogen with:
- Oxides of sulphur
- Hydrogen sulphide
- Oxides of phosphorus
- Unburnt hydrocarbons
Show answer and explanation
Answer: D. Unburnt hydrocarbons
PAN, a photochemical smog component, forms from the reaction of NOₓ with unburnt hydrocarbons in sunlight.
Volume occupied by 2g of SO₂ gas at S.T.P will be:
- 17dm³
- 0.7dm³
- 0.7cm³
- 700dm³
Show answer and explanation
Answer: B. 0.7dm³
Moles of SO₂ (M=64) = 2/64 = 0.03125 mol; V = 0.03125 × 22.4 dm³/mol ≈ 0.7 dm³.
Which pair of gases diffuses with the same rate at same temperature and pressure?
- CO and PH₃
- CO and NO
- NO and C₂H₆
- NH₃ and PH₃
Show answer and explanation
Answer: C. NO and C₂H₆
By Graham's law, equal diffusion rate needs equal molar mass. NO (30 g/mol) and C₂H₆ (30 g/mol) have the same molar mass.
Which of the following is NOT present in plasma?
- Neutral atoms
- Electrons
- Cations
- Anions
Show answer and explanation
Answer: D. Anions
Plasma is an ionized gas of roughly equal numbers of cations and free electrons; it does not contain bound anions.
Calculate the volume of 177.5 g of chlorine gas at STP.
Show model answer
Moles Cl₂ = 177.5/71 = 2.5 mol.
Volume at STP = moles × 22.4 L/mol = 2.5 × 22.4 = 56 L (dm³)
Calculate the numerical value of general gas constant 'R' for one mole of gas at S.T.P: (i) In SI units (ii) Pressure in atm, volume in dm³
Show model answer
(i) SI units: R = PV/nT = (101325 Pa × 0.0224 m³)/(1 mol × 273 K) = 8.314 J K⁻¹ mol⁻¹
(ii) Atm, dm³ units: R = PV/nT = (1 atm × 22.4 dm³)/(1 mol × 273 K) = 0.0821 dm³ atm K⁻¹ mol⁻¹
Sessions with Gases questions
| Session | Questions |
|---|---|
| 2026 Annual | 2 |
| 2025 1st Annual | 3 |
| 2025 2nd Annual | 1 |
| 2024 Annual | 9 |
| 2023 Annual | 3 |
Common questions
What does the Gases chapter cover on this page?
18 real Federal Board (FBISE) Chemistry questions on Gases 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
- Liquids 18
- Carbonyl compounds 18
- Alkyl Halides 18
- Thermochemistry 17
- Carboxylic acids 17
- Reaction Kinetics 16
- Environmental Chemistry 16
- s-Block/Group IV-A elements 15