Introduction
Preparing for Class 10 Chemistry CBSE board exams is not just about memorizing reactions. It’s about understanding concepts, identifying patterns in questions, and practicing smartly. This guide brings together the most important questions. It is designed to help you revise faster, strengthen your conceptual understanding, and boost your confidence for the board exam.
To fully understand the concepts, detailed explanations, and step-by-step solving of all 33 important questions, make sure to watch the complete video. It will help you build deeper conceptual clarity and perform better in your board exams.
Most Important Topics for Class 10 Chemistry Boards
Chemical Reactions and Equations
- Balancing chemical equations
- Types of reactions (combination, decomposition, displacement, double displacement)
- Exothermic and endothermic reactions
- Oxidation and reduction (redox reactions)
Acids, Bases and Salts
- pH scale and its significance
- Strength of acids and bases
- Chemical properties of acids and bases
- Salts and their hydrolysis
- Indicators (natural, synthetic, olfactory)
Metals and Non-Metals
- Reactivity series of metals
- Properties of metals and non-metals
- Ionic compounds and their properties
- Corrosion and its prevention
- Extraction and uses of metals
Carbon and Its Compounds
- Covalent bonding and properties
- Homologous series
- Hydrocarbons (alkanes, alkenes, alkynes)
- Functional groups and nomenclature
- Important reactions (combustion, oxidation, esterification, hydrogenation)
33 Most Important Questions Are
Chemical Reactions & Equations
Q1. Balance the equation involving water and hydrogen.
Answer: x = 4, y = 4
Explanation: Balance oxygen first (4 O), then hydrogen (8 H), ensuring both sides are equal.
Q2. Reaction of sodium hydroxide with zinc.
Answer: NaOH + Zn → Sodium zincate + H₂
Explanation: Zinc reacts with NaOH to form sodium zincate and hydrogen gas.
Q3. Match gases with tests.
Answer: NO₂ → brown fumes, CO₂ → extinguishes fire, O₂ → supports combustion, SO₂ → pungent smell, H₂ → pop sound
Explanation: Standard identification tests for gases.
Q4. Identify non-combination reactions.
Answer: Burning of natural gas and respiration
Explanation: Combination reactions produce a single product; these produce multiple products.
Q5. Reaction of BaCl₂ with Na₂SO₄.
Answer: BaCl₂ + Na₂SO₄ → BaSO₄↓ + 2NaCl
Explanation: White precipitate forms; this is a double displacement reaction.
Q6. Quicklime with water.
Answer: CaO + H₂O → Ca(OH)₂ + heat
Explanation: Combination and exothermic reaction.
Q7. Assertion: Copper forms black substance.
Answer: Both true and reason correct
Explanation: Copper reacts with oxygen to form black CuO.
Q8. Identify X, Y, Z in reaction.
Answer: X = Cu, Y = CuO, Z = Cu
Explanation: Copper oxidizes to CuO and reduces back with hydrogen.
Acids, Bases & Salts
Q9. Calcium carbonate formula substances.
Answer: Limestone, chalk, marble
Explanation: All have formula CaCO₃.
Q10. Reaction producing CO₂ with acetic acid.
Answer: Sodium carbonate / sodium bicarbonate
Explanation: These release CO₂ with acids.
Q11. Non-olfactory indicators.
Answer: Phenolphthalein and methyl orange
Explanation: They change color, not smell.
Q12. Salt with pH > 7.
Answer: Na₂CO₃
Explanation: Formed from strong base and weak acid.
Q13. Assertion: CuO + HCl gives blue-green solution.
Answer: Both true and correct explanation
Explanation: CuCl₂ formed is bluish-green.
Q14. pH changes.
Answer: Both true but not correct explanation
Explanation: One refers to base, other to acid.
Q15. Na₂CO₃ + HCl reaction.
Answer: NaHCO₃ forms
Explanation: Red litmus turns blue due to basic nature.
Q16. Why acidified water conducts electricity?
Answer: Due to presence of ions
Explanation: H⁺ ions carry current.
Q17. Dissociation of KOH.
Answer: KOH → K⁺ + OH⁻
Explanation: Strong base dissociates completely.
Metals & Non-Metals
Q18. Metal reacting with water.
Answer: pH increases
Explanation: Base is formed.
Q19. Ca and Mg float on water.
Answer: Due to H₂ bubbles
Explanation: Gas sticks to metal surface.
Q20. Aqua regia incorrect statement.
Answer: Wrong ratio statement
Explanation: Correct ratio is 1:3 (HNO₃:HCl).
Q21. Thermite reaction incorrect statement.
Answer: Aluminium is low reactive (incorrect)
Explanation: Aluminium is highly reactive.
Q22. Silver turns black.
Answer: Formation of Ag₂S
Explanation: Reaction with H₂S in air.
Q23. Copper turns green.
Answer: Formation of CuCO₃
Explanation: Reaction with CO₂ and moisture.
Q24. Why gold and silver used in jewellery?
Answer: Malleable, ductile, less reactive
Explanation: Suitable physical properties.
Q25. Why few metals used in cooking utensils?
Answer: High melting point, good conductor
Explanation: Ensures durability and efficiency.
Q26. Reaction with dilute HNO₃.
Answer: Assertion true, reason false
Explanation: HNO₃ is oxidizing agent.
Q27. Ionic compounds high melting point.
Answer: Both true and correct explanation
Explanation: Strong electrostatic forces.
Carbon Compounds
Q28. Covalent bonds in C₆H₁₄.
Answer: 19 bonds
Explanation: Count total C–C and C–H bonds.
Q29. Triple bond in alkynes.
Answer: C₃H₄
Explanation: Follows formula CnH2n-2.
Q30. Incorrect statement about hydrogenation.
Answer: Oils are saturated (incorrect)
Explanation: Oils are unsaturated.
Q31. Blackened cooking vessel.
Answer: Incomplete combustion
Explanation: Produces soot.
Q32. Sweet smell in ice cream.
Answer: Ester (ethyl ethanoate)
Explanation: Formed by esterification.
Q33. Homologous series property.
Answer: Difference of CH₂ unit
Explanation: Successive members differ by CH₂.
Q34. Saturated vs unsaturated flame.
Answer: Both true but not explanation
Explanation: Not directly related.
Q35. Soap behavior.
Answer: Assertion true, reason false
Explanation: Soap ineffective in hard water.
Q36. Vegetable oil vs animal fat.
Answer: Oil = unsaturated, fat = saturated
Explanation: Unsaturated fats are healthier.
Q37. Hydrogenation reaction.
Answer: Addition of H₂ in presence of catalyst
Explanation: Converts unsaturated to saturated.
Key Preparation Tips for Chemistry Boards
- Focus on important reactions, equations, and repeated questions
- Practice balancing equations and writing reactions daily
- Revise NCERT examples and in-text questions thoroughly
- Understand concepts instead of memorizing blindly
- Practice assertion-reason and MCQs regularly
Common Mistakes to Avoid
- Not balancing chemical equations correctly
- Confusing types of reactions (e.g., displacement vs double displacement)
- Ignoring NCERT-based questions
- Weak understanding of pH, salts, and indicators
- Memorizing reactions without understanding concepts
Smart Study Strategy for CBSE Chemistry
- Prioritize high-weightage chapters like Reactions and Carbon Compounds
- Practice previous year questions regularly
- Focus on conceptual clarity and reaction mechanisms
- Revise daily using short notes and reaction charts
FAQs
Q1. Which chapter is most important in Chemistry?
Chemical Reactions and Carbon Compounds are highly important.
Q2. Are assertion-reason questions common?
Yes, they are frequently asked in CBSE exams.
Q3. How to score high in Chemistry?
Practice reactions, understand concepts, and revise NCERT thoroughly.
Q4. Are numericals important in Chemistry?
Yes, especially in pH and mole concept-based questions.
Conclusion
Your board exam score will largely depend on how well you revise in these final days. Don’t try to cover everything – focus on these high-impact questions, revise them multiple times, and make sure you understand the logic behind each one. Even a small mistake in basics can cost marks, so stay sharp and practice with full concentration.
If you are serious about scoring high, don’t skip the detailed explanations – watch the complete video and practice along with it. This final revision can be the difference between an average score and a top score.
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