Number of atoms in 8g He are:
- 6.02×10²²
- 1.204×10²⁴
- 6.02×10²¹
- 1.204×10²³
Show answer and explanation
Answer: B. 1.204×10²⁴
8 g He ÷ 4 g/mol = 2 mol; 2 mol × 6.02×10²³ = 1.204×10²⁴ atoms.
FSC Chemistry: Basic Concepts, questions with answers
Practise 53 real Federal Board questions on Basic Concepts from 2023 to 2026. See the answer and explanation as soon as you answer.
53real questions
20multiple choice
5exam sessions
About Basic Concepts in FSC Chemistry
Basic Concepts is one of the 19 main chapters in our Federal Board FSC Chemistry question bank (11th class), and about 11% of its real questions come from it. Tayyari Karo has 53 real questions on this chapter from 2023 to 2026; 20 are multiple choice and marked instantly, and the rest are short and long questions with a model answer. By difficulty: 30 medium, 14 easy, 9 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.
Free radical substitution occurs in:
- Alkene
- Alcohol
- Alkane
- Carboxylic Acid
Show answer and explanation
Answer: C. Alkane
Alkanes (saturated, only C-H/C-C bonds) undergo free-radical substitution reactions, e.g. halogenation under UV light.
Which product is formed by reduction of Propanone by NaBH₄?
- 1-propanol
- 2-propanol
- Propanoic acid
- Propanal
Show answer and explanation
Answer: B. 2-propanol
NaBH₄ reduces the ketone propanone (CH₃COCH₃) to the secondary alcohol 2-propanol (CH₃CH(OH)CH₃).
The reactant that determines the maximum yield of a chemical reaction is called the:
- Excess reactant
- By-product
- Catalyst
- Limiting reactant
Show answer and explanation
Answer: D. Limiting reactant
The limiting reactant is consumed first and thus caps (determines) the maximum possible product yield.
The reaction of methane with chlorine in the presence of sunlight is an example of:
- Electrophilic addition
- Free radical substitution
- Nucleophilic substitution
- Elimination
Show answer and explanation
Answer: B. Free radical substitution
CH₄ + Cl₂ under UV/sunlight proceeds via a free-radical chain (initiation/propagation/termination) substitution mechanism.
Aldehydes can be oxidized to:
- Carboxylic acids
- Ketones
- Alcohols
- Esters
Show answer and explanation
Answer: A. Carboxylic acids
Mild oxidation of an aldehyde (-CHO) converts it to the corresponding carboxylic acid (-COOH).
How acetic acid and ethanol react to form an ester? Write the complete reaction.
Show model answer
Acetic acid and ethanol undergo acid-catalyzed (conc. H₂SO₄) esterification (Fischer esterification), with loss of water:
CH₃COOH + C₂H₅OH --(conc. H₂SO₄, Δ)--> CH₃COOC₂H₅ (ethyl acetate) + H₂O
Write chemical equation for the preparation of alkyl halides: a. From Alkenes b. From Alkanes
Show model answer
a. From alkenes (addition of HX): CH₂=CH₂ + HBr → CH₃CH₂Br
b. From alkanes (free-radical halogenation): CH₄ + Cl₂ --(UV light)--> CH₃Cl + HCl
Sessions with Basic Concepts questions
| Session | Questions |
|---|---|
| 2026 Annual | 21 |
| 2025 1st Annual | 1 |
| 2025 2nd Annual | 23 |
| 2024 Annual | 5 |
| 2023 Annual | 3 |
Common questions
What does the Basic Concepts chapter cover on this page?
53 real Federal Board (FBISE) Chemistry questions on Basic Concepts 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
- 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
- Thermochemistry 17
- Carboxylic acids 17
- Reaction Kinetics 16
- Environmental Chemistry 16
- s-Block/Group IV-A elements 15