Class 10 Chemistry PYQ Master Guide (2015–2025)
Chemistry is one of the highest-scoring sections of the CBSE Class 10 Science examination. Analysis of board examination papers over the last decade shows that many concepts are repeatedly tested in different forms.(CBSE Class 10 Chemistry PYQs)
Students who prepare these repeated questions thoroughly often find a significant portion of the Chemistry paper familiar during the examination.
Table of Contents ( CBSE Class 10 Chemistry PYQs )
- Introduction
- Why Study Repeated PYQs?
- Important Abbreviations
- Quick Revision Facts
- Chemical Reactions and Equations
- Acids, Bases and Salts
- Metals and Non-Metals
- Carbon and Its Compounds
- Periodic Classification of Elements
- Top Repeated Board Questions
- One-Line Revision Notes
- Exam Preparation Tips
- Conclusion
Important Abbreviations ( CBSE Class 10 Chemistry PYQs )
| Abbreviation | Full Form |
|---|---|
| pH | Potential of Hydrogen |
| HCl | Hydrochloric Acid |
| H₂SO₄ | Sulphuric Acid |
| NaOH | Sodium Hydroxide |
| NaHCO₃ | Sodium Hydrogen Carbonate |
| CaOCl₂ | Calcium Oxychloride |
| LPG | Liquefied Petroleum Gas |
| CNG | Compressed Natural Gas |
| PVC | Polyvinyl Chloride |
| IUPAC | International Union of Pure and Applied Chemistry |
Quick Revision Facts ( CBSE Class 10 Chemistry PYQs )
| Rusting requires oxygen and moisture. |
| Sodium is stored in kerosene |
| Graphite conducts electricity. |
| Diamond is the hardest natural substance |
| pH less than 7 indicates acidity. |
| Carbon is tetravalent. |
| Noble gases are chemically stable. |
| Soap forms scum in hard water. |
Chapter 1: Chemical Reactions and Equations
Question 1
Why should magnesium ribbon be cleaned before burning?
Answer (English)
Magnesium ribbon develops a layer of magnesium oxide when exposed to air. This layer prevents proper burning.
उत्तर (हिंदी)
वायु के संपर्क में आने पर मैग्नीशियम रिबन की सतह पर मैग्नीशियम ऑक्साइड की परत बन जाती है, जो इसके जलने में बाधा डालती है।
Question 2
What is a combination reaction?
Answer
A reaction in which two or more substances combine to form a single product.
Example
CaO + H₂O → Ca(OH)₂
हिंदी
जिस अभिक्रिया में दो या अधिक पदार्थ मिलकर एक उत्पाद बनाते हैं उसे संयोजन अभिक्रिया कहते हैं।
Question 3
What is a decomposition reaction?
Answer
A reaction in which a compound breaks down into simpler substances.
Example
2AgCl → 2Ag + Cl₂
हिंदी
जिस अभिक्रिया में एक यौगिक टूटकर सरल पदार्थों में बदल जाता है उसे अपघटन अभिक्रिया कहते हैं।
Question 4
Define oxidation and reduction.
Answer
Oxidation:
Addition of oxygen or removal of hydrogen.
Reduction:
Removal of oxygen or addition of hydrogen.
हिंदी
ऑक्सीकरण:
ऑक्सीजन का जुड़ना या हाइड्रोजन का हटना।
अपचयन:
ऑक्सीजन का हटना या हाइड्रोजन का जुड़ना।
Chapter 2: Acids, Bases and Salts
Question 5
What is pH?
Answer
pH is a scale used to measure acidity and basicity.
हिंदी
pH किसी विलयन की अम्लीयता एवं क्षारीयता को मापने का पैमाना है।
Question 6
Why does tooth decay occur below pH 5.5?
Answer
At low pH, acids start dissolving the enamel of teeth.
हिंदी
कम pH पर अम्ल दांतों की एनामेल परत को नुकसान पहुंचाते हैं।
Question 7
What is baking soda?
Answer
Sodium Hydrogen Carbonate
Formula: NaHCO₃
हिंदी
बेकिंग सोडा का रासायनिक नाम सोडियम हाइड्रोजन कार्बोनेट है।
Question 8
Uses of Baking Soda
Answer
- Baking cakes
- Antacid
- Fire extinguishers
हिंदी
- केक बनाने में
- अम्लता दूर करने में
- अग्निशामक यंत्रों में
Question 9
What is bleaching powder?
Answer
Calcium Oxychloride (CaOCl₂)
Uses
- Water purification
- Textile industry
- Disinfectant
हिंदी
ब्लीचिंग पाउडर का रासायनिक नाम कैल्शियम ऑक्सीक्लोराइड है।
Chapter 3: Metals and Non-Metals
Question 10
Why is sodium stored in kerosene oil?
Answer
Sodium reacts rapidly with oxygen and moisture present in air.
हिंदी
सोडियम वायु में उपस्थित ऑक्सीजन और नमी से तेजी से प्रतिक्रिया करता है।
Question 11
Name a metal that can be cut with a knife.
Answer
Sodium
हिंदी
सोडियम
Question 12
Define alloy.
Answer
An alloy is a homogeneous mixture of metals or a metal and a non-metal.
हिंदी
मिश्रधातु दो या अधिक धातुओं अथवा धातु एवं अधातु का समांगी मिश्रण है।
Question 13
What is corrosion?
Answer
Gradual destruction of metals due to chemical reactions with the environment.
हिंदी
पर्यावरण के साथ रासायनिक प्रतिक्रिया के कारण धातुओं का धीरे-धीरे नष्ट होना संक्षारण कहलाता है।
Question 14
Methods to Prevent Corrosion
Answer
- Painting
- Oiling
- Greasing
- Galvanization
हिंदी
- पेंट करना
- तेल लगाना
- ग्रीस लगाना
- जस्तीकरण
Chapter 4: Carbon and Its Compounds
Question 15
Why does carbon form covalent bonds?
Answer
Carbon has four valence electrons and cannot easily gain or lose four electrons.
हिंदी
कार्बन के बाहरी कोश में चार इलेक्ट्रॉन होते हैं। इसलिए यह सहसंयोजक बंध बनाता है।
Question 16
What is tetravalency?
Answer
The ability of carbon to form four covalent bonds.
हिंदी
कार्बन की चार सहसंयोजक बंध बनाने की क्षमता को चतुसंयोजकता कहते हैं।
Question 17
Define homologous series.
Answer
A series of compounds having similar chemical properties and differing by CH₂ group.
हिंदी
ऐसे यौगिकों की श्रेणी जिनके रासायनिक गुण समान हों तथा क्रमागत सदस्यों में CH₂ का अंतर हो।
Question 18
First Four Members of Alkane Series
- Methane
- Ethane
- Propane
- Butane
हिंदी
- मीथेन
- एथेन
- प्रोपेन
- ब्यूटेन
Question 19
Difference Between Saturated and Unsaturated Hydrocarbons
| Saturated | Unsaturated |
|---|---|
| Single Bond | Double/Triple Bond |
| Less Reactive | More Reactive |
Question 20
Difference Between Soap and Detergent
| Soap | Detergent |
|---|---|
| Forms scum in hard water | Effective in hard water |
| Biodegradable | May not be biodegradable |
Chapter 5: Periodic Classification of Elements
Question 21
Who proposed the Modern Periodic Law?
Answer
Henry Moseley
हिंदी
हेनरी मोसले
Question 22
How many groups are present in the modern periodic table?
Answer
18 Groups
हिंदी
18 समूह
Question 23
How many periods are present?
Answer
7 Periods
हिंदी
7 आवर्त
Question 24
Why are noble gases chemically inert?
Answer
Because their outermost electron shell is complete.
हिंदी
क्योंकि उनका बाह्यतम इलेक्ट्रॉन कोश पूर्ण होता है।
Top 10 Board Examination PYQs ( CBSE Class 10 Chemistry PYQs )
- Why is magnesium ribbon cleaned before burning?
- Define pH.
- Why is sodium stored in kerosene?
- What is corrosion?
- Explain rusting.
- Define homologous series.
- What is tetravalency?
- Differentiate between soap and detergent.
- What is bleaching powder?
- State Modern Periodic Law.
One-Line Revision Notes ( CBSE Class 10 Chemistry PYQs )
- Rusting is oxidation of iron.
- pH 7 indicates neutrality.
- Carbon is tetravalent.
- Diamond is hardest.
- Graphite conducts electricity.
- NaHCO₃ is baking soda.
- CaOCl₂ is bleaching powder.
- Sodium is highly reactive.
- Noble gases are stable.
- Alloys improve properties of metals.
Exam Preparation Tips
English
- Learn all chemical equations.
- Practice NCERT in-text questions.
- Revise definitions daily.
- Focus on diagrams and activities.
हिंदी
- सभी रासायनिक समीकरण याद करें।
- NCERT के प्रश्नों का अभ्यास करें।
- प्रतिदिन परिभाषाओं का पुनरावृत्ति करें।
- गतिविधियों और चित्रों पर विशेष ध्यान दें।
Conclusion
The analysis of CBSE Chemistry questions from 2015–2025 reveals that many concepts are repeatedly tested. Students who master these repeated questions gain a strong advantage in the board examination. Consistent revision, NCERT practice, and PYQ analysis remain the keys to success.
हिंदी निष्कर्ष
2015–2025 के CBSE Chemistry प्रश्नपत्रों के अध्ययन से स्पष्ट है कि कुछ महत्वपूर्ण अवधारणाएँ लगातार पूछी जाती हैं। यदि विद्यार्थी इन प्रश्नों का गहन अभ्यास करें, तो बोर्ड परीक्षा में उत्कृष्ट अंक प्राप्त कर सकते हैं।
© Rising Star Mindset
www.risingstarmindset.com
Empowering Students Through Quality Education