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Practice Class 10 Science Chapter 1 Chemical Reactions and Equations MCQ Questions with Answers based on the latest NCERT syllabus. Solve important MCQs on rancidity, corrosion, decomposition reactions, reaction indicators, and redox reactions with detailed solutions for CBSE, State Board, Olympiad, and scholarship exams.
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Chapter Information
Subject: Science
Class: 10
Chapter: Chemical Reactions and Equations
Question Type: Multiple Choice Questions (MCQs)
Difficulty Level: Moderate to Difficult
Based On: NCERT Latest Syllabus (2026)
Introduction
Chemical reactions play an important role in daily life. From food spoilage and rusting of metals to energy production and industrial processes, chemical changes affect the world around us. Understanding these concepts helps students build a strong foundation in chemistry.
What You Will Learn
✔ Rancidity and its prevention
✔ Corrosion and metal protection
✔ Decomposition reactions
✔ Redox reactions
✔ Characteristics of chemical reactions
✔ Everyday chemistry applications
✔ NCERT-based concepts
Why This Topic Is Important?
This chapter forms the foundation of chemistry in Class 10 Science. Concepts such as oxidation, corrosion, decomposition, and reaction indicators are frequently asked in CBSE Board Exams, school tests, Olympiads, and scholarship examinations.
1. MCQ Questions with Detailed Solutions
Q1. Which gas is commonly used to prevent rancidity in packaged food items?
A) Oxygen
B) Carbon Dioxide
C) Nitrogen
D) Hydrogen
Answer
C) Nitrogen
Concept Behind This Question
Nitrogen is less reactive and prevents oxidation of food.
Step-by-Step Solution
Rancidity occurs when fats and oils react with oxygen.
Food packets are filled with nitrogen gas to reduce contact with oxygen.
Therefore, the correct answer is:
Nitrogen
Exam Tip
Potato chips packets are commonly filled with nitrogen gas.
Q2. Which of the following is an example of a decomposition reaction?
A) $$2H_2 + O_2 \rightarrow 2H_2O$$
B) $$CaO + H_2O \rightarrow Ca(OH)_2$$
C) $$2AgBr \rightarrow 2Ag + Br_2$$
D) $$Fe + CuSO_4 \rightarrow FeSO_4 + Cu$$
Answer
C) $$2AgBr \rightarrow 2Ag + Br_2$$
Concept Behind This Question
A decomposition reaction breaks one compound into simpler substances.
Step-by-Step Solution
Silver bromide breaks down into silver and bromine.
$$2AgBr \rightarrow 2Ag + Br_2$$
One reactant forms multiple products.
Therefore, it is a decomposition reaction.
Exam Tip
Silver bromide decomposition is caused by sunlight.
Q3. Which of the following is NOT a characteristic of a chemical reaction?
A) Formation of new substances
B) Change in temperature
C) Evolution of gas
D) Change in size of an object only
Answer
D) Change in size of an object only
Concept Behind This Question
A chemical reaction must involve chemical change, not merely physical change.
Step-by-Step Solution
A change in size alone does not create a new substance.
It is generally a physical change.
Therefore, it is not considered a characteristic of a chemical reaction.
Exam Tip
Look for signs such as gas evolution, colour change, precipitate formation, or temperature change.
Q4. In the reaction below, which substance is reduced?
$$CuO + H_2 \rightarrow Cu + H_2O$$
A) Hydrogen
B) Water
C) Copper Oxide
D) Copper
Answer
C) Copper Oxide
Concept Behind This Question
Reduction means removal of oxygen.
Step-by-Step Solution
Copper oxide loses oxygen and forms copper.
$$CuO \rightarrow Cu$$
Loss of oxygen indicates reduction.
Therefore, copper oxide is reduced.
Exam Tip
Remember: Reduction = Loss of oxygen.
Q5. Which method prevents rusting by isolating iron from air and moisture?
A) Galvanization
B) Painting
C) Both A and B
D) None of these
Answer
C) Both A and B
Concept Behind This Question
Protective coatings prevent oxygen and moisture from reaching iron.
Step-by-Step Solution
Painting forms a protective layer.
Galvanization coats iron with zinc.
Both methods prevent contact with oxygen and moisture.
Therefore, both help prevent rusting.
Exam Tip
Any protective coating can reduce corrosion.
Important Formulas & Concepts
1. Rancidity
Oxidation of fats and oils resulting in unpleasant smell and taste.
2. Decomposition Reaction
A single compound breaks into simpler substances.
Example:
$$2AgBr \rightarrow 2Ag + Br_2$$
3. Oxidation
Addition of oxygen or removal of hydrogen.
4. Reduction
Removal of oxygen or addition of hydrogen.
5. Corrosion Prevention
• Painting
• Galvanization
• Greasing
• Alloying
Related Practice Questions
- What is rancidity?
- Why is nitrogen used in food packaging?
- Define decomposition reaction.
- What is reduction?
- How can rusting be prevented?
Mini Quiz Challenge
Fill in the blanks
- Nitrogen helps prevent __________.
- Silver bromide undergoes __________ reaction.
- Loss of oxygen is called __________.
Answers
- Rancidity
- Decomposition
- Reduction
Exam Tips
✔ Revise all reaction types from NCERT.
✔ Learn important examples of oxidation and reduction.
✔ Remember corrosion-prevention methods.
✔ Focus on observation-based chemistry questions.
✔ Practice balancing equations regularly.
Quick Revision Notes
✔ Nitrogen prevents rancidity.
✔ Silver bromide undergoes photochemical decomposition.
✔ Chemical reactions produce new substances.
✔ Reduction means loss of oxygen.
✔ Painting and galvanization prevent rusting.
✔ Gas evolution indicates a chemical reaction.
✔ Corrosion damages metal surfaces.
Common Mistakes Students Make
❌ Confusing rancidity with corrosion.
❌ Forgetting the role of nitrogen in food packaging.
❌ Mixing oxidation and reduction definitions.
❌ Ignoring signs of chemical reactions.
❌ Confusing physical changes with chemical changes.
Key Takeaways
✔ Nitrogen prevents oxidation of food products.
✔ Decomposition reactions break compounds into simpler substances.
✔ Reduction involves loss of oxygen.
✔ Rusting can be prevented using protective coatings.
✔ Chemical reactions are identified through observable changes.
✔ Understanding NCERT examples improves examination performance.
FAQs
1. What is rancidity?
The oxidation of fats and oils that causes food spoilage.
2. Why are food packets filled with nitrogen?
To prevent oxidation and rancidity.
3. What is a decomposition reaction?
A reaction in which one compound breaks into simpler substances.
4. What is reduction?
Removal of oxygen or addition of hydrogen.
5. How can rusting be prevented?
By painting, galvanization, greasing, or alloying.
Conclusion
Chemical reactions influence many everyday processes, including food preservation, corrosion, and energy production. Understanding decomposition, oxidation, reduction, and corrosion-prevention methods helps students build strong chemistry fundamentals and prepare effectively for examinations.
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