Class 10 Science QP Worksheet Chapter 1 Chemical Reactions and Equations | Detailed Solutions & Marking Scheme
VEDANT WORKSHEET SERIES - ACADEMIC
YEAR 2026-27
CLASS X | SCIENCE
(086)
CHAPTER 1: CHEMICAL REACTIONS AND EQUATIONS
Time Allowed: 1
Hour | Maximum Marks: 30
SECTION A (1 × 7 = 7 Marks)
1. Which of the following represents a balanced chemical
equation?
(a) H2 + O2 → H2O
(b) 2H2 + O2 → 2H2O
(c) H2 + O2 → H2O2
(d) H2 + O → H2O
2. The reaction in which two or more substances combine
to form a single product is called:
(a) Decomposition reaction
(b) Combination reaction
(c) Displacement reaction
(d) Redox reaction
3. Identify the type of reaction:
CaCO3 → CaO + CO2
(a) Combination
(b) Decomposition
(c) Displacement
(d) Double displacement
4. Which of the following is an example of a
precipitation reaction?
(a) Zn + CuSO4 → ZnSO4 + Cu
(b) AgNO3 + NaCl → AgCl↓ + NaNO3
(c) C + O2 → CO2
(d) H2 + Cl2 → 2HCl
5. Which of the following is an exothermic reaction?
(a) Photosynthesis
(b) Thermal decomposition of CaCO3
(c) Combustion of methane
(d) Electrolysis of water
6. Assertion (A): Oxidation involves loss of electrons.
Reason (R): Reduction involves gain of electrons.
A. Both A and R are true, R is correct explanation of A
B. Both A and R are true, R is not correct explanation of A
C. A is true, R is false
D. A is false, R is true
7. Assertion (A): Rusting of iron is a chemical change.
Reason (R): It involves formation of a new substance.
A. Both A and R are true, R is correct explanation of A
B. Both A and R are true, R is not correct explanation of A
C. A is true, R is false
D. A is false, R is true
SECTION B (2 × 4 = 8 Marks)
8. Write any two observations which indicate that a
chemical reaction has taken place. Give suitable examples.
9. Balance the following chemical equation:
Fe + H2O → Fe3O4 + H2
10. Identify the type of reaction and define it:
Zn + CuSO4 → ZnSO4 + Cu
11. Differentiate between exothermic and endothermic
reactions with one example each.
SECTION C (3 × 2 = 6 Marks)
12. Write the steps involved in balancing a chemical
equation. Illustrate with an example.
13. Explain oxidation and reduction with suitable
examples. Also identify oxidizing and reducing agents in the reaction:
CuO + H2 → Cu + H2O
SECTION D (5 × 1 = 5 Marks)
14. Explain the following types of chemical reactions
with one balanced equation each:
(a) Combination reaction
(b) Decomposition reaction
(c) Displacement reaction
(d) Double displacement reaction
(e) Redox reaction
SECTION E (CASE STUDY) (4 Marks)
15. Case Study:
A student performed an experiment by mixing aqueous
solutions of barium chloride and sodium sulphate. A white precipitate was
formed immediately. The reaction is represented as:
BaCl2 + Na2SO4 → BaSO4↓ + 2NaCl
Based on the above information, answer the following
questions:
(a) What type of reaction is this? (1 mark)
(b) What is the name of the white precipitate formed?
(1 mark)
(c) Explain why this reaction is also called a double
displacement reaction. (2 marks)
ANSWER KEY WITH DETAILED MARKING SCHEME
CLASS X | SCIENCE
CHAPTER 1: CHEMICAL REACTIONS AND EQUATIONS
SECTION A (1 × 7 = 7 Marks)
1. (b) 2H2 + O2 → 2H2O
Marks: 1
2. (b) Combination reaction
Marks: 1
3. (b) Decomposition
Marks: 1
4. (b) AgNO3 + NaCl → AgCl↓ + NaNO3
Marks: 1
5. (c) Combustion of methane
Marks: 1
6. (A) Oxidation involves loss of electrons.
(R) Reduction involves gain of electrons.
Correct Option: A
Explanation: Both are correct and define redox processes.
Marks: 1
7. (A) Rusting is a chemical change.
(R) New substance (iron oxide) is formed.
Correct Option: A
Marks: 1
SECTION B (2 × 4 = 8 Marks)
8. Observations indicating chemical reaction (Any two):
• Change in colour (e.g., Fe + CuSO4 → FeSO4 + Cu, blue to green)
• Evolution of gas (e.g., Zn + HCl → ZnCl2 + H2↑)
• Formation of precipitate
• Change in temperature
Marking Scheme:
Any 2 points = 1 mark each
Example included = 1 mark
Total: 2 marks
9. Balanced Equation:
3Fe + 4H2O → Fe3O4 + 4H2
Marking Scheme:
Correct balancing = 2 marks
10. Reaction Type:
Displacement reaction
Definition:
A reaction in which a more reactive element displaces a less reactive element from its compound.
Marking Scheme:
Type = 1 mark
Definition = 1 mark
Total: 2 marks
11. Difference between Exothermic & Endothermic:
Exothermic Reaction:
• Heat is released
• Example: CH4 + 2O2 → CO2 + 2H2O + heat
Endothermic Reaction:
• Heat is absorbed
• Example: CaCO3 → CaO + CO2
Marking Scheme:
Definition (each) = 0.5 + 0.5
Example (each) = 0.5 + 0.5
Total: 2 marks
SECTION C (3 × 2 = 6 Marks)
12. Steps to balance chemical equation:
- Write skeletal equation
- List atoms on both sides
- Balance metals
- Balance non-metals
- Balance hydrogen and oxygen
- Check and verify
Example:
Fe + H2O → Fe3O4 + H2
Balanced: 3Fe + 4H2O → Fe3O4 + 4H2
Marking Scheme:
Steps = 2 marks
Example = 1 mark
Total: 3 marks
13. Oxidation and Reduction:
Oxidation: Loss of electrons / gain of oxygen
Reduction: Gain of electrons / loss of oxygen
Reaction: CuO + H2 → Cu + H2O
• CuO → Cu (Reduction)
• H2 → H2O (Oxidation)
Oxidizing agent: CuO
Reducing agent: H2
Marking Scheme:
Definitions = 1 mark
Identification = 1 mark
Agents = 1 mark
Total: 3 marks
SECTION D (5 × 1 = 5 Marks)
14. Types of Reactions:
(a) Combination:
2H2 + O2 → 2H2O
(b) Decomposition:
CaCO3 → CaO + CO2
(c) Displacement:
Zn + CuSO4 → ZnSO4 + Cu
(d) Double Displacement:
Na2SO4 + BaCl2 → BaSO4 + 2NaCl
(e) Redox Reaction:
CuO + H2 → Cu + H2O
Marking Scheme:
Each correct definition + equation = 1 mark
Total: 5 marks
SECTION E (CASE STUDY) (4 Marks)
15.
(a) Type of reaction:
Precipitation reaction
Marks: 1
(b) White precipitate:
Barium sulphate (BaSO4)
Marks: 1
(c) Explanation:**
In this reaction, ions of two compounds exchange their positions to form two new compounds.
Ba²⁺ combines with SO4²⁻ to form BaSO4 (precipitate), while Na⁺ combines with Cl⁻ to form NaCl.
Marking Scheme:
Explanation (exchange of ions + product formation) = 2 marks
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