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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 by electricity, displacement reactions, respiration, corrosion prevention, and balancing chemical 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 occur continuously around us. Some reactions are useful and provide energy, while others may damage materials over time. Understanding different types of reactions helps students explain natural phenomena and industrial processes scientifically.
What You Will Learn
✔ Electrolytic decomposition
✔ Displacement reactions
✔ Respiration as a chemical reaction
✔ Prevention of corrosion
✔ Balancing chemical equations
✔ Everyday applications of chemistry
✔ Reaction analysis skills
Why This Topic Is Important?
Chemical reactions are fundamental to science and technology. Knowledge of these reactions helps students understand industrial manufacturing, energy production, food preservation, and environmental processes. This chapter is highly important for board examinations.
1. MCQ Questions with Detailed Solutions
Q1. Which process causes the decomposition of water into hydrogen and oxygen?
A) Heating only
B) Cooling
C) Passing electric current
D) Filtration
Answer
C) Passing electric current
Concept Behind This Question
Some compounds decompose when electricity is passed through them.
Step-by-Step Solution
Water can be decomposed by electrolysis:
$$2H_2O \rightarrow 2H_2 + O_2$$
This process requires electric current.
Therefore, the correct answer is:
Passing electric current
Exam Tip
Electrolysis is a common example of decomposition using electricity.
Q2. Which metal can displace iron from iron sulphate solution?
A) Copper
B) Silver
C) Magnesium
D) Gold
Answer
C) Magnesium
Useful Concept for this Question
A more reactive metal displaces a less reactive metal from its compound.
Step-by-Step Solution
Magnesium is more reactive than iron.
Therefore:
$$Mg + FeSO_4 \rightarrow MgSO_4 + Fe$$
Magnesium successfully displaces iron.
Exam Tip
Learn the reactivity series for displacement reactions.
Q3. Respiration is an example of which type of reaction?
A) Endothermic Reaction
B) Exothermic Reaction
C) Neutralization Reaction
D) Decomposition Reaction
Answer
B) Exothermic Reaction
Concept Behind This Question
Respiration releases energy stored in food.
Step-by-Step Solution
During respiration:
$$C_6H_{12}O_6 + O_2 \rightarrow CO_2 + H_2O + Energy$$
Energy is released.
Therefore, respiration is an exothermic reaction.
Exam Tip
Respiration is one of the most important biological examples of an exothermic reaction.
Q4. Which method is commonly used to prevent rusting of iron?
A) Heating
B) Washing with water
C) Painting
D) Breaking into pieces
Answer
C) Painting
Concept Behind This Question
Rusting requires contact with oxygen and moisture.
Step-by-Step Solution
Painting forms a protective layer on iron.
This layer prevents contact with air and moisture.
As a result, rusting is reduced.
Therefore, the correct answer is:
Painting
Exam Tip
Painting, galvanization, and greasing are common methods of rust prevention.
Q5. Which of the following equations is correctly balanced?
A) $$H_2 + Cl_2 \rightarrow HCl$$
B) $$H_2 + Cl_2 \rightarrow 2HCl$$
C) $$2H_2 + Cl_2 \rightarrow HCl$$
D) $$H_2 + 2Cl_2 \rightarrow HCl$$
Answer
B) $$H_2 + Cl_2 \rightarrow 2HCl$$
Useful Formula for this Question
Atoms of each element must be equal on both sides.
Step-by-Step Solution
Left side:
Hydrogen = 2
Chlorine = 2
Right side:
$$2HCl$$
Hydrogen = 2
Chlorine = 2
Atoms are equal on both sides.
Hence, the equation is balanced.
Exam Tip
Count atoms carefully before deciding whether an equation is balanced.
Important Formulas & Concepts
1. Electrolytic Decomposition
Decomposition caused by electric current.
Example:
$$2H_2O \rightarrow 2H_2 + O_2$$
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. Rusting
Slow oxidation of iron in the presence of air and moisture.
5. Corrosion Prevention Methods
• Painting
• Galvanization
• Greasing
• Alloy formation
Related Practice Questions
- What is electrolysis?
- Why is magnesium more reactive than iron?
- Why is respiration called an exothermic reaction?
- Name two methods of preventing rusting.
- What is the importance of balancing equations?
Mini Quiz Challenge
Fill in the blanks
- Water decomposes into hydrogen and __________ during electrolysis.
- Rusting requires oxygen and __________.
- Respiration releases __________.
Answers
- Oxygen
- Moisture
- Energy
Exam Tips
✔ Revise all examples of decomposition reactions.
✔ Learn practical methods of corrosion prevention.
✔ Remember important balanced equations from NCERT.
✔ Understand the reactivity series of metals.
✔ Practice identifying reaction types from equations.
Quick Revision Notes
✔ Electricity can decompose water into hydrogen and oxygen.
✔ Magnesium is more reactive than iron.
✔ Respiration is an exothermic reaction.
✔ Painting prevents rusting.
✔ Balanced equations have equal atoms on both sides.
✔ Corrosion damages metals gradually.
✔ Reaction types are frequently asked in board exams.
Common Mistakes Students Make
❌ Confusing electrolysis with heating.
❌ Forgetting the conditions required for rusting.
❌ Mixing exothermic and endothermic reactions.
❌ Ignoring the reactivity series.
❌ Counting atoms incorrectly while balancing equations.
Key Takeaways
✔ Electric current can cause decomposition reactions.
✔ More reactive metals displace less reactive metals.
✔ Respiration releases energy.
✔ Rusting can be prevented by protective coatings.
✔ Balanced equations follow the law of conservation of mass.
✔ Understanding reaction types improves exam performance.
FAQs
1. What is electrolysis?
The process of decomposition using electric current.
2. Why does iron rust?
Because iron reacts with oxygen and moisture.
3. Why is respiration exothermic?
Because it releases energy during the breakdown of food.
4. How can rusting be prevented?
By painting, galvanization, or greasing.
5. Why should chemical equations be balanced?
To ensure equal numbers of atoms on both sides.
Conclusion
Chemical reactions affect our daily lives in many ways. Understanding electrolysis, displacement reactions, respiration, rusting, and balanced equations helps students develop a strong conceptual foundation and perform confidently in examinations.
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