Class 10 Science MCQ Test – Chemical Reactions and Equations (Chapter 1) | Full Chapter Test

Class 10 Science – Chapter 1: Chemical Reactions and Equations (Detailed Notes)

These notes are designed for CBSE & GSEB students. Covers complete theory, reactions, examples, and exam-oriented concepts.

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1. What is a Chemical Reaction?

A chemical reaction is a process in which one or more substances (reactants) are converted into new substances (products) with different properties.

Example:

\( Mg + O_2 \rightarrow MgO \)

Here, Magnesium reacts with Oxygen to form Magnesium Oxide.

Characteristics of Chemical Reactions

• Change in colour
• Evolution of gas
• Change in temperature (heat absorbed/released)
• Formation of precipitate
• Change in state

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2. Chemical Equations

A chemical equation is the symbolic representation of a chemical reaction.

Types of Equations

• Word Equation: Magnesium + Oxygen → Magnesium Oxide
• Skeletal Equation: \( Mg + O_2 \rightarrow MgO \)
• Balanced Equation: \( 2Mg + O_2 \rightarrow 2MgO \)

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3. Balanced Chemical Equations

A balanced equation has equal number of atoms of each element on both sides.

Based on Law of Conservation of Mass.

Steps to Balance Equation

• Write skeletal equation
• Balance metals
• Balance non-metals
• Balance hydrogen and oxygen last
• Check atoms on both sides

Example:

\( Fe + H_2O \rightarrow Fe_3O_4 + H_2 \)

Balanced:

\( 3Fe + 4H_2O \rightarrow Fe_3O_4 + 4H_2 \)

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4. Types of Chemical Reactions

1. Combination Reaction

Two or more substances combine to form a single product.

\( CaO + H_2O \rightarrow Ca(OH)_2 \)

2. Decomposition Reaction

A compound breaks into simpler substances.

\( CaCO_3 \xrightarrow{\Delta} CaO + CO_2 \)

• Thermal decomposition
• Electrolytic decomposition
• Photolytic decomposition

3. Displacement Reaction

A more reactive element displaces a less reactive element.

\( Zn + CuSO_4 \rightarrow ZnSO_4 + Cu \)

4. Double Displacement Reaction

Exchange of ions between two compounds.

\( Na_2SO_4 + BaCl_2 \rightarrow BaSO_4 \downarrow + 2NaCl \)

\( BaSO_4 \) is a precipitate.

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5. Exothermic and Endothermic Reactions

Exothermic Reaction

Heat is released.

\( C + O_2 \rightarrow CO_2 + Heat \)

Endothermic Reaction

Heat is absorbed.

\( N_2 + O_2 \rightarrow 2NO - Heat \)

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6. Oxidation and Reduction

Oxidation

• Addition of oxygen
• Removal of hydrogen

Reduction

• Removal of oxygen
• Addition of hydrogen

Example:

\( CuO + H_2 \rightarrow Cu + H_2O \)

• \( CuO \) → Reduced
• \( H_2 \) → Oxidised

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7. Corrosion

Slow destruction of metals due to reaction with environment.

Example: Rusting of iron

\( 4Fe + 3O_2 + xH_2O \rightarrow 2Fe_2O_3 \cdot xH_2O \)

Prevention

• Painting
• Oiling/Greasing
• Galvanization

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8. Rancidity

Oxidation of fats and oils leading to bad smell and taste.

Prevention

• Use antioxidants
• Refrigeration
• Air-tight containers

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9. Important Exam Points

• Always balance equations correctly
• Remember reaction types with examples
• Understand oxidation-reduction clearly
• Use proper symbols: \( \Delta \), \( \downarrow \), \( \uparrow \)
• Corrosion and rancidity are frequently asked

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⬇️ Attempt the test given below after revising these notes

Class 10 Science

Chapter 1: Chemical Reactions and Equations | Full Chapter Test

Time Left: 05:00

Student Name:

1. Which of the following represents a balanced chemical equation?

Fe + H₂O → Fe₃O₄ + H₂ 3Fe + 4H₂O → Fe₃O₄ + 4H₂ Fe + 4H₂O → Fe₃O₄ + 4H₂ 2Fe + H₂O → Fe₂O₃ + H₂

2. The reaction CaO + H₂O → Ca(OH)₂ is an example of:

Decomposition reaction Combination reaction Displacement reaction Double displacement reaction

3. Which reaction is an example of a precipitation reaction?

Na₂SO₄ + BaCl₂ → BaSO₄↓ + 2NaCl C + O₂ → CO₂ CaCO₃ → CaO + CO₂ Fe + CuSO₄ → FeSO₄ + Cu

4. Which of the following is an endothermic reaction?

Burning of methane Respiration Thermal decomposition of CaCO₃ Neutralisation reaction

5. Which substance undergoes oxidation in the reaction: Zn + CuSO₄ → ZnSO₄ + Cu ?

Zn Cu²⁺ SO₄²⁻ Cu

6. Which type of reaction is represented by: 2AgCl → 2Ag + Cl₂ ?

Combination Decomposition Displacement Precipitation

7. Which reaction is a displacement reaction?

Fe + CuSO₄ → FeSO₄ + Cu CaO + H₂O → Ca(OH)₂ Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl CaCO₃ → CaO + CO₂

8. Which process represents reduction?

Gain of oxygen Loss of hydrogen Gain of hydrogen Loss of electrons

9. Which reaction releases heat?

Photosynthesis Electrolysis of water Combustion of coal Thermal decomposition

10. The reaction Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl is:

Combination reaction Decomposition reaction Double displacement reaction Displacement reaction

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