NCERT Solutions for Class 10 Science Chapter 1: Chemical Reactions and Equations

Chemical Reactions and Equations is the foundation of your Class 10 Science journey. This chapter introduces the fundamental concepts of how substances interact, change, and form new products. Scoring well in this chapter is crucial for your board exams because it forms the basis for subsequent chapters like Acids, Bases, and Salts, and Metals and Non-metals. If you haven't grasped the theoretical concepts yet, make sure to check out our full chapter notes to strengthen your basics before diving into these solutions.

As per the official NCERT syllabus, understanding the chemical change and the ability to balance equations is a core competency expected from every CBSE student. Mastering this will ensure you don't lose marks on basic chemical representations.

Understanding Chemical Reactions and Balanced Equations

Before we jump into the textbook exercises, it is important to remember that a balanced chemical equation satisfies the Law of Conservation of Mass—total mass of elements on the reactant side must equal the total mass on the product side.

In-Text Question 1: Why should a magnesium ribbon be cleaned before burning in air?

Answer: Magnesium reacts with oxygen in the atmosphere to form a protective layer of magnesium oxide (MgO) on its surface. This layer prevents further reaction or makes it difficult to ignite the ribbon. Cleaning it with sandpaper removes this layer, allowing the metal to react easily with oxygen.

In-Text Question 2: Write the balanced equation for: Hydrogen + Chlorine → Hydrogen Chloride

Answer:

• Skeleton Equation: H₂ + Cl₂ → HCl
• Balanced Equation: H₂ + Cl₂ → 2HCl

Types of Chemical Reactions

Understanding the classification of reactions—combination, decomposition, displacement, and double displacement—is vital. If you find yourself struggling with these types, you can browse all chapter notes on our platform to clarify your doubts.

Exercise Question: What is the difference between a displacement and a double displacement reaction?

Answer:

• Displacement Reaction: A more reactive element displaces a less reactive element from its compound.
  • Example: Fe + CuSO₄ → FeSO₄ + Cu
• Double Displacement Reaction: Two compounds exchange their ions to form two new compounds.
  • Example: Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl

Step-by-Step Textbook Exercise Solutions

For students aiming for high scores, consistent practice is key. We highly recommend utilizing our NCERT solutions hub to cross-verify your answers as you prepare for your final exams.

Question: Why is respiration considered an exothermic reaction?

Answer: During respiration, glucose (C₆H₁₂O₆) combines with oxygen in our body cells to provide energy. Since energy (in the form of heat/ATP) is released during this process, it is classified as an exothermic reaction. Chemical Equation: C₆H₁₂O₆(aq) + 6O₂(g) → 6CO₂(g) + 6H₂O(l) + Energy

Question: A shiny brown colored element 'X' on heating in air becomes black in colour. Name the element 'X' and the black coloured compound formed.

Answer:

• Element 'X' is Copper (Cu).
• The black colored compound formed is Copper(II) oxide (CuO).
• Reaction: 2Cu + O₂ → 2CuO

Tips to Score Full Marks in Board Exams

Securing a perfect score in Class 10 Science requires more than just memorizing equations. Follow these expert strategies:

• Practice Balancing Regularly: Every exam paper has at least one balancing question. Don't leave easy marks on the table.
• Highlight the State Symbols: Always write (s), (l), (g), and (aq) alongside your chemical formulas. This is a standard requirement set by the CBSE guidelines.
• Use Flowcharts: When explaining types of reactions, use simple flowcharts or bullet points to make your answers visually organized for examiners.
• Test Yourself: Regular self-assessment is the best way to track progress. Attempt our practice tests to simulate the exam environment and manage your time effectively.
• Focus on Keywords: Highlight key terms like "oxidation," "reduction," "precipitate," and "exothermic" in your answers.

Frequently Asked Questions

What is the most important topic in Chapter 1 for the CBSE board exam?

The most important topics are balancing chemical equations and identifying the type of chemical reaction (specifically redox, displacement, and decomposition reactions).

Is it necessary to memorize all equations in the textbook?

While you don't need to memorize the entire book, you must be familiar with the equations used as examples in the text. Often, questions are derived directly from these examples.

What is a redox reaction?

A redox reaction is a chemical process where oxidation (addition of oxygen/removal of hydrogen) and reduction (removal of oxygen/addition of hydrogen) take place simultaneously.

How do I identify a precipitation reaction?

A precipitation reaction is a type of double displacement reaction where an insoluble solid (precipitate) is formed when two solutions are mixed together. Look for keywords like "insoluble" or "white precipitate" in the question.

Why does the color of copper sulphate solution change when an iron nail is dipped in it?

It is a displacement reaction. Iron is more reactive than copper, so it displaces copper from the copper sulphate solution, forming ferrous sulphate, which is green in color, while the original blue color fades.

Conclusion

Mastering Chapter 1 is the first step toward building a strong profile for your board exams. By focusing on the mechanics of chemical changes and practicing the balanced equations regularly, you build the logic required for higher-level chemistry. Remember, consistency is the difference between an average student and a topper. Use the resources available on Explore CircleOfLearning to stay ahead of your curriculum.

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