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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 exothermic reactions, respiration, precipitation reactions, corrosion, 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 occur all around us—from respiration in our bodies to industrial manufacturing processes. Studying these reactions helps students understand how substances change and how energy is released or absorbed during chemical transformations.
What You Will Learn
✔ Exothermic reactions
✔ Respiration as a chemical reaction
✔ Precipitation reactions
✔ Corrosion and prevention
✔ Balancing equations
✔ Daily-life applications of chemistry
✔ Concept-based problem solving
Why This Topic Is Important?
This chapter introduces fundamental chemistry concepts that are essential for higher classes. Questions from exothermic reactions, corrosion, and reaction identification are commonly asked in school exams, board exams, Olympiads, and scholarship tests.
1. MCQ Questions with Detailed Solutions
Q1. Which of the following is an example of an exothermic reaction?
A) Photosynthesis
B) Electrolysis of water
C) Respiration
D) Decomposition of calcium carbonate
Answer
C) Respiration
Concept Behind This Question
Exothermic reactions release energy.
Step-by-Step Solution
During respiration, glucose reacts with oxygen:
$$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + Energy$$
Energy is released.
Therefore, respiration is an exothermic reaction.
Exam Tip
Respiration is one of the most important NCERT examples of an exothermic reaction.
Q2. A white precipitate is formed when silver nitrate solution reacts with sodium chloride solution. The precipitate formed is:
A) Sodium Nitrate
B) Silver Chloride
C) Sodium Chloride
D) Silver Oxide
Answer
B) Silver Chloride
Useful Formula for this Question
$$AgNO_3 + NaCl \rightarrow AgCl + NaNO_3$$
Step-by-Step Solution
Silver ions combine with chloride ions.
This forms insoluble silver chloride:
$$AgCl$$
A white precipitate appears.
Therefore, the correct answer is silver chloride.
Exam Tip
Silver chloride is a white precipitate frequently asked in examinations.
Q3. Which factor is necessary for rusting of iron?
A) Nitrogen only
B) Carbon dioxide only
C) Oxygen and moisture
D) Sunlight only
Answer
C) Oxygen and moisture
Concept Behind This Question
Rusting requires both oxygen and water.
Step-by-Step Solution
Iron reacts with oxygen in the presence of moisture.
Without moisture, rusting becomes very slow.
Therefore, oxygen and moisture are essential.
Exam Tip
Remember: Rusting = Oxygen + Moisture + Iron.
Q4. Which of the following is a balanced chemical equation?
A) $$H_2 + O_2 \rightarrow H_2O$$
B) $$2H_2 + O_2 \rightarrow 2H_2O$$
C) $$H_2 + O_2 \rightarrow 2H_2O$$
D) $$H_2 + 2O_2 \rightarrow H_2O$$
Answer
B) $$2H_2 + O_2 \rightarrow 2H_2O$$
Concept Behind This Question
Balanced equations contain equal numbers of atoms on both sides.
Step-by-Step Solution
Reactants:
Hydrogen = 4
Oxygen = 2
Products:
Hydrogen = 4
Oxygen = 2
Therefore, the equation is balanced.
Exam Tip
Always count atoms carefully before choosing an answer.
Q5. Which reaction is represented by the equation?
$$AgNO_3 + NaCl \rightarrow AgCl + NaNO_3$$
A) Combination Reaction
B) Decomposition Reaction
C) Double Displacement Reaction
D) Combustion Reaction
Answer
C) Double Displacement Reaction
Concept Behind This Question
The ions exchange partners to form new compounds.
Step-by-Step Solution
Silver nitrate and sodium chloride exchange ions.
Products formed:
• Silver chloride
• Sodium nitrate
Therefore, it is a double displacement reaction.
Exam Tip
Exchange of ions is the key feature of double displacement reactions.
Important Formulas & Concepts
1. Exothermic Reaction
A reaction that releases heat energy.
Example:
$$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + Energy$$
2. Precipitation Reaction
A reaction that produces an insoluble solid called a precipitate.
3. Rusting Conditions
• Iron
• Oxygen
• Moisture
4. Double Displacement Reaction
$$AB + CD \rightarrow AD + CB$$
5. Balanced Equation Rule
Number of atoms of each element must remain equal on both sides.
Related Practice Questions
- Why is respiration called an exothermic reaction?
- What is a precipitate?
- Which conditions are required for rusting?
- Define double displacement reaction.
- Why must equations be balanced?
Mini Quiz Challenge
Fill in the blanks
- Respiration is an __________ reaction.
- Silver chloride forms a __________ precipitate.
- Rusting requires oxygen and __________.
Answers
- Exothermic
- White
- Moisture
Exam Tips
✔ Learn all NCERT examples of exothermic reactions.
✔ Revise precipitation reactions carefully.
✔ Remember the conditions required for rusting.
✔ Practice balancing equations daily.
✔ Focus on reaction identification questions.
Quick Revision Notes
✔ Respiration releases energy.
✔ Silver chloride forms a white precipitate.
✔ Rusting requires oxygen and moisture.
✔ Balanced equations obey conservation of mass.
✔ Double displacement reactions involve ion exchange.
✔ Precipitation reactions form insoluble solids.
✔ Chemical reactions produce new substances.
Common Mistakes Students Make
❌ Confusing exothermic and endothermic reactions.
❌ Forgetting the colour of silver chloride precipitate.
❌ Ignoring moisture as a condition for rusting.
❌ Incorrectly balancing simple equations.
❌ Mixing double displacement with combination reactions.
Key Takeaways
✔ Respiration is an exothermic reaction.
✔ Silver chloride is a white precipitate.
✔ Rusting requires oxygen and moisture.
✔ Balanced equations have equal atoms on both sides.
✔ Double displacement reactions involve exchange of ions.
✔ Understanding reaction observations improves exam performance.
FAQs
1. Why is respiration exothermic?
Because it releases energy during the breakdown of glucose.
2. What is a precipitate?
An insoluble solid formed during a chemical reaction.
3. Why is silver chloride important?
It is a common example of a precipitation reaction.
4. What conditions are necessary for rusting?
Oxygen and moisture.
5. What is a double displacement reaction?
A reaction in which two compounds exchange ions.
Conclusion
Chemical reactions are responsible for energy production, material changes, and many natural processes. Understanding exothermic reactions, precipitation reactions, rusting, and balanced equations helps students build strong chemistry fundamentals and succeed in examinations.
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