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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 decomposition reactions, displacement reactions, exothermic reactions, oxidation, and balancing equations 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 can occur in different ways depending on the substances involved. Some reactions release heat, some absorb heat, while others produce entirely new substances. Understanding these reactions helps students explain many natural and industrial processes around them.
What You Will Learn
✔ Decomposition reactions
✔ Displacement reactions
✔ Exothermic reactions
✔ Endothermic reactions
✔ Oxidation and corrosion
✔ Balancing chemical equations
✔ Practical applications of chemical reactions
Why This Topic Is Important
Chemical reactions are essential in daily life, industries, agriculture, medicine, and environmental science. Understanding reaction types improves analytical thinking and helps students solve board exam and competitive exam questions confidently.
1. MCQ Questions with Detailed Solutions
Q1. Which of the following is a decomposition reaction?
A) $$2Mg + O_2 \rightarrow 2MgO$$
B) $$CaCO_3 \rightarrow CaO + CO_2$$
C) $$Zn + CuSO_4 \rightarrow ZnSO_4 + Cu$$
D) $$HCl + NaOH \rightarrow NaCl + H_2O$$
Answer
B) $$CaCO_3 \rightarrow CaO + CO_2$$
Concept Behind This Question
A decomposition reaction occurs when a single compound breaks down into two or more simpler substances.
Step-by-Step Solution
In the reaction:
$$CaCO_3 \rightarrow CaO + CO_2$$
One compound produces two products.
Therefore, it is a decomposition reaction.
Exam Tip
One reactant forming multiple products usually indicates decomposition.
Q2. Which metal displaces copper from copper sulphate solution?
A) Silver
B) Gold
C) Zinc
D) Platinum
Answer
C) Zinc
Useful Concept for this Question
A more reactive metal displaces a less reactive metal from its compound.
Step-by-Step Solution
Reaction:
$$Zn + CuSO_4 \rightarrow ZnSO_4 + Cu$$
Zinc is more reactive than copper.
Therefore, zinc displaces copper from copper sulphate solution.
Exam Tip
Remember the reactivity series of metals.
Q3. Which reaction releases heat energy?
A) Exothermic Reaction
B) Endothermic Reaction
C) Neutral Reaction
D) Reversible Reaction
Answer
A) Exothermic Reaction
Concept Behind This Question
Exothermic reactions release heat into the surroundings.
Step-by-Step Solution
Examples:
• Burning of coal
• Respiration
• Combustion of fuels
All release heat energy.
Therefore, they are exothermic reactions.
Exam Tip
“Exo” means outside. Heat goes out of the system.
Q4. What is the balanced coefficient of oxygen in the equation?
$$4Fe + O_2 \rightarrow 2Fe_2O_3$$
A) 2
B) 3
C) 4
D) 5
Answer
B) 3
Useful Formula for this Question
Number of atoms must be equal on both sides.
Step-by-Step Solution
Balanced equation:
$$4Fe + 3O_2 \rightarrow 2Fe_2O_3$$
Check oxygen atoms:
Left side:
$$3 \times 2 = 6$$
Right side:
$$2 \times 3 = 6$$
Oxygen coefficient =
$$3$$
Exam Tip
Always balance oxygen atoms at the end whenever possible.
Q5. Which process is responsible for the green coating on copper utensils?
A) Reduction
B) Corrosion
C) Neutralization
D) Sublimation
Answer
B) Corrosion
Concept Behind This Question
Copper reacts with air, moisture, and carbon dioxide to form a green layer.
Step-by-Step Solution
Copper forms basic copper carbonate on exposure to air.
This process is known as corrosion.
Therefore, the correct answer is corrosion.
Exam Tip
Green coating on copper and rusting of iron are examples of corrosion.
Important Formulas & Concepts
1. Decomposition Reaction
$$AB \rightarrow A + B$$
A compound breaks into simpler substances.
2. Displacement Reaction
$$A + BC \rightarrow AC + B$$
A more reactive element replaces a less reactive element.
3. Exothermic Reaction
A reaction that releases heat energy.
4. Endothermic Reaction
A reaction that absorbs heat energy.
5. Corrosion
Slow deterioration of metals due to chemical reactions with the environment.
Related Practice Questions
- Define decomposition reaction with an example.
- What is the difference between exothermic and endothermic reactions?
- Why does zinc displace copper from copper sulphate?
- What is corrosion?
- Give one example of a displacement reaction.
Mini Quiz Challenge
Fill in the blanks
- A reaction that absorbs heat is called __________ reaction.
- Zinc is __________ reactive than copper.
- Green coating on copper is caused by __________.
Answers
- Endothermic
- More
- Corrosion
Exam Tips
✔ Learn reaction types with examples.
✔ Practice balancing equations regularly.
✔ Remember the metal reactivity series.
✔ Understand the difference between oxidation and corrosion.
✔ Focus on NCERT examples and activities.
Quick Revision Notes
✔ Decomposition reactions break compounds into simpler substances.
✔ Displacement reactions involve more reactive elements replacing less reactive ones.
✔ Exothermic reactions release heat.
✔ Endothermic reactions absorb heat.
✔ Corrosion damages metals over time.
✔ Zinc can displace copper from copper sulphate.
✔ Balanced equations obey the law of conservation of mass.
Common Mistakes Students Make
❌ Confusing decomposition and displacement reactions.
❌ Forgetting to balance oxygen atoms properly.
❌ Mixing corrosion with oxidation.
❌ Ignoring the reactivity series.
❌ Memorizing reactions without understanding concepts.
Key Takeaways
✔ Decomposition reactions produce multiple products.
✔ More reactive metals displace less reactive metals.
✔ Exothermic reactions release heat energy.
✔ Corrosion affects metal surfaces.
✔ Balanced equations maintain equal atoms on both sides.
✔ Understanding reaction types helps solve exam questions quickly.
FAQs
1. What is a decomposition reaction?
A reaction in which a compound breaks into simpler substances.
2. What is a displacement reaction?
A reaction where a more reactive element replaces a less reactive element.
3. What is corrosion?
The gradual damage of metals due to chemical reactions with the environment.
4. What is an exothermic reaction?
A reaction that releases heat energy.
5. Why is balancing important?
It ensures the law of conservation of mass is followed.
Conclusion
Understanding decomposition, displacement, exothermic reactions, and corrosion helps students build a strong foundation in Chemistry. Regular practice of MCQs improves problem-solving skills and prepares students for CBSE, State Board, Olympiad, and scholarship examinations.
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