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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 silver bromide decomposition, reaction balancing, combustion, oxidation, and chemical reaction observations 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 be identified through various observable changes such as colour change, temperature change, gas evolution, and precipitate formation. This chapter helps students understand how these reactions occur and how they can be represented using balanced chemical equations.
What You Will Learn
✔ Silver bromide decomposition
✔ Combustion reactions
✔ Balancing chemical equations
✔ Oxidation in everyday life
✔ Observation-based chemistry
✔ Chemical reaction indicators
✔ Practical applications of reactions
Why This Topic Is Important?
Understanding chemical reactions is essential for learning advanced chemistry concepts. The topics covered in this chapter frequently appear in school examinations, board exams, Olympiads, and scholarship tests.
1. MCQ Questions with Detailed Solutions
Q1. Silver bromide is used in photography because it:
A) Dissolves easily in water
B) Reacts with acids quickly
C) Decomposes in sunlight
D) Produces oxygen gas
Answer
C) Decomposes in sunlight
Concept Behind This Question
Silver bromide is a photosensitive compound.
Step-by-Step Solution
Silver bromide decomposes when exposed to sunlight:
$$2AgBr \rightarrow 2Ag + Br_2$$
This property makes it useful in photographic films.
Therefore, the correct answer is:
Decomposes in sunlight
Exam Tip
Silver chloride and silver bromide are important examples of photosensitive compounds.
Q2. Which coefficient balances the equation?
$$N_2 + H_2 \rightarrow NH_3$$
A) $$N_2 + H_2 \rightarrow 2NH_3$$
B) $$N_2 + 2H_2 \rightarrow 2NH_3$$
C) $$N_2 + 3H_2 \rightarrow 2NH_3$$
D) $$2N_2 + H_2 \rightarrow 2NH_3$$
Answer
C) $$N_2 + 3H_2 \rightarrow 2NH_3$$
Useful Formula for this Question
Number of atoms must be equal on both sides.
Step-by-Step Solution
Left side:
Nitrogen = 2
Hydrogen = 6
Right side:
$$2NH_3$$
Nitrogen = 2
Hydrogen = 6
Therefore, the equation is balanced.
Exam Tip
Balance nitrogen first, then hydrogen.
Q3. Burning of natural gas is an example of:
A) Combination Reaction
B) Combustion Reaction
C) Decomposition Reaction
D) Reduction Reaction
Answer
B) Combustion Reaction
Concept Behind This Question
Combustion occurs when a substance burns in oxygen.
Step-by-Step Solution
Natural gas reacts with oxygen and releases heat and light.
This process is called combustion.
Therefore, the correct answer is:
Combustion Reaction
Exam Tip
All combustion reactions are exothermic.
Q4. Which of the following is NOT an indicator of a chemical reaction?
A) Gas evolution
B) Formation of precipitate
C) Change in colour
D) Change in shape of an object
Answer
D) Change in shape of an object
Concept Behind This Question
A change in shape alone usually represents a physical change.
Step-by-Step Solution
Gas formation, colour change, and precipitate formation indicate chemical reactions.
Changing only the shape does not produce a new substance.
Therefore, it is not a reliable indicator of a chemical reaction.
Exam Tip
Chemical reactions always involve the formation of new substances.
Q5. Which substance gains oxygen in the reaction below?
$$2Cu + O_2 \rightarrow 2CuO$$
A) Oxygen
B) Copper
C) Copper Oxide
D) None of these
Answer
B) Copper
Concept Behind This Question
Addition of oxygen is oxidation.
Step-by-Step Solution
Copper reacts with oxygen:
$$2Cu + O_2 \rightarrow 2CuO$$
Copper gains oxygen and forms copper oxide.
Therefore, copper undergoes oxidation.
Exam Tip
Gain of oxygen = Oxidation.
Important Formulas & Concepts
1. Photosensitive Compounds
Compounds that decompose in sunlight.
Examples:
$$AgCl,\ AgBr$$
2. Combustion Reaction
A substance reacts with oxygen and releases heat.
3. Balanced Equation Rule
Number of atoms on both sides must be equal.
4. Oxidation
Addition of oxygen or removal of hydrogen.
5. Indicators of Chemical Reactions
• Colour change
• Gas evolution
• Temperature change
• Precipitate formation
Related Practice Questions
- Why is silver bromide used in photography?
- Define combustion reaction.
- What is oxidation?
- How do you identify a chemical reaction?
- Why should chemical equations be balanced?
Mini Quiz Challenge
Fill in the blanks
- Silver bromide is a __________ compound.
- Burning of fuels is a __________ reaction.
- Gain of oxygen is called __________.
Answers
- Photosensitive
- Combustion
- Oxidation
Exam Tips
✔ Learn all photosensitive compounds from NCERT.
✔ Practice balancing equations daily.
✔ Revise oxidation and reduction definitions.
✔ Remember the signs of chemical reactions.
✔ Focus on application-based questions.
Quick Revision Notes
✔ Silver bromide decomposes in sunlight.
✔ Photographic films use silver bromide.
✔ Combustion reactions release heat energy.
✔ Oxidation involves gain of oxygen.
✔ Balanced equations have equal atoms on both sides.
✔ Chemical reactions produce new substances.
✔ Colour change often indicates a chemical reaction.
Common Mistakes Students Make
❌ Confusing combustion with combination reactions.
❌ Forgetting balanced coefficients.
❌ Mixing physical changes with chemical changes.
❌ Ignoring oxidation definitions.
❌ Memorizing equations without understanding concepts.
Key Takeaways
✔ Silver bromide is photosensitive.
✔ Combustion reactions release energy.
✔ Chemical equations must be balanced.
✔ Oxidation involves gain of oxygen.
✔ Chemical reactions can be identified through observable changes.
✔ Understanding reaction indicators improves problem-solving ability.
FAQs
1. Why is silver bromide used in photography?
Because it decomposes when exposed to sunlight.
2. What is a combustion reaction?
A reaction in which a substance burns in oxygen and releases energy.
3. What is oxidation?
Addition of oxygen or removal of hydrogen.
4. Why are balanced equations important?
They follow the law of conservation of mass.
5. What are the common signs of a chemical reaction?
Colour change, gas evolution, temperature change, and precipitate formation.
Conclusion
Chemical reactions are identified through several observable changes and play an important role in daily life. Understanding photosensitive compounds, combustion reactions, balancing equations, and oxidation helps students build strong chemistry fundamentals and improve examination performance.
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