MCQs for Class 10 Science Chapter 1 Chemical Reactions and Equations

 introduces students to the Chemical Reactions and Equationse basic concepts of chemistry, including balancing chemical equations, types of chemical reactions, oxidation, and reduction. Understanding these topics helps students build a strong foundation in Class 10 Science and prepare for board exams. Practicing Chemical Reactions and Equations Class 10 MCQs improves conceptual clarity, accuracy, and confidence in solving objective questions.

Regular practice helps students revise important concepts and understand the reasoning behind each answer. Students can explore MCQs and Class 10 MCQs for chapter-wise practice. They can also refer to CBSE Board resources and Class 10 Science MCQs to strengthen their preparation according to the latest syllabus and exam pattern.

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MCQs for Class 10 Science Chapter 1 with Answers and Explanations 

Practising Chemical Reactions and Equations Class 10 MCQs is one of the most effective ways to prepare for the CBSE board exam. These objective questions help students understand important concepts like balancing equations, identifying reaction types, oxidation and reduction, corrosion, and rancidity in a more practical way. Solving MCQs regularly also improves speed, accuracy, and confidence while attempting exam-based chemistry questions.

Q1. A chemical reaction in which two or more substances combine to form a single product is called:

A. Displacement reaction
B. Combination reaction
C. Decomposition reaction
D. Neutralisation reaction

Answer: B

Explanation:
A combination reaction takes place when multiple reactants join together to produce one product. These reactions usually release energy in the form of heat or light.

Q2. A student heats ferrous sulphate crystals in a test tube. The crystals first lose water and then decompose. Which type of reaction is involved?
A. Combination reaction
B. Thermal decomposition reaction
C. Double displacement reaction
D. Neutralisation reaction

Answer: B

Explanation:
When heat causes a compound to break into simpler substances, the process is called thermal decomposition. Ferrous sulphate decomposes on strong heating.

Q3. Which of the following substances acts as a reactant in the formation of magnesium oxide?
A.Carbon dioxide
B. Magnesium
C. Calcium carbonate
D. Sodium chloride

Answer: B

Explanation:
Magnesium reacts with oxygen present in air to produce magnesium oxide. The substances taking part in the reaction are known as reactants.

Q4. In a balanced chemical equation, the total number of atoms remains:
A. Different on both sides
B. Equal on both sides
C. Zero on product side
D. Double on reactant side

Answer: B

Explanation:
According to the law of conservation of mass, atoms cannot be created or destroyed during a chemical reaction. Therefore, the number of atoms remains equal on both sides.

Q5. What is observed when magnesium ribbon burns in air?
A.Green flame with black ash
B. Yellow flame with brown residue
C. Bright white flame with white powder
D. Blue flame with gas evolution

Answer: C

Explanation:
Magnesium burns with a dazzling white flame and forms magnesium oxide, which appears as a white powdery ash.

Q6. Which gas is commonly released when zinc reacts with dilute hydrochloric acid?
A.Oxygen
B. Hydrogen
C. Nitrogen
D. Carbon dioxide

Answer: B

Explanation:
Zinc reacts with dilute hydrochloric acid to produce zinc chloride and hydrogen gas. Hydrogen is colourless and burns with a popping sound.

Q7. A reaction where one metal replaces another metal from its salt solution is known as:
A.Combination reaction
B. Redox reaction
C. Displacement reaction
D. Decomposition reaction

Answer: C

Explanation:
In a displacement reaction, a more reactive metal replaces a less reactive metal from its compound or solution.

Q8. Which of the following is the correct chemical formula for aluminium oxide?
A. AlO
B. Al₂O₃
C. AlO₂
D. Al₃O₂

Answer: B

Explanation:
Aluminium combines with oxygen in the ratio required to balance their valencies, forming aluminium oxide with the formula Al₂O₃.

Q9. What happens when carbon dioxide gas is passed through lime water?
A. Lime water becomes colourless
B. Blue precipitate forms
C. Lime water turns milky
D. Hydrogen gas evolves

Answer: C

Explanation:
Carbon dioxide reacts with calcium hydroxide in lime water to form calcium carbonate, which gives a milky appearance.

Q10. Which process is considered a chemical change?

A. Breaking glass
B. Boiling water
C. Rusting of iron
D. Cutting paper

Answer: C

Explanation:
Rusting forms a new substance called hydrated iron oxide. Since a new substance is produced, it is a chemical change.

Q11. The reaction between silver nitrate and sodium chloride produces a white precipitate of:

A. Silver oxide
B. Silver chloride
C. Sodium nitrate
D. Sodium oxide

Answer: B

Explanation:
When silver nitrate reacts with sodium chloride, insoluble silver chloride is formed as a white precipitate.

Q12. Oxidation in a chemical reaction involves:

A. Gain of oxygen
B. Loss of oxygen
C. Gain of electrons
D. Removal of hydrogen only

Answer: A

Explanation:
Oxidation commonly refers to the addition of oxygen to a substance or removal of hydrogen from it.

Q13. Which type of reaction occurs when electricity is used to split water into hydrogen and oxygen?
A. Combination reaction
B. Electrolytic decomposition reaction
C. Displacement reaction
D. Neutralisation reaction

Answer: B

Explanation:
Electric current causes water molecules to break into hydrogen and oxygen gases. This process is called electrolytic decomposition.

Q14. A brown gas is released when lead nitrate is heated strongly. The gas is:

A. Hydrogen
B. Nitrogen dioxide
C. Sulphur dioxide
D. Oxygen

Answer: B

Explanation:
Lead nitrate decomposes on heating to produce lead oxide, oxygen, and nitrogen dioxide gas, which appears brown in colour.

Q15. Which of the following reactions is an example of a combination reaction?

A. CaCO₃ → CaO + CO₂
B. Zn + CuSO₄ → ZnSO₄ + Cu
C. 2Mg + O₂ → 2MgO
D. AgNO₃ + NaCl → AgCl + NaNO₃

Answer: C

Explanation:
In this reaction, magnesium and oxygen combine to form a single product, magnesium oxide, making it a combination reaction.

Q16. Food items containing oils and fats are flushed with nitrogen gas mainly to:

A. Increase flavour
B. Reduce weight
C. Prevent rancidity
D. Improve colour

Answer: C

Explanation:
Nitrogen prevents oxidation of fats and oils, reducing the chances of rancidity and increasing shelf life.

Q17. Which observation indicates that a chemical reaction has taken place?

A. Change in shape only
B. Formation of gas
C. Increase in size
D. Breaking into pieces

Answer: B

Explanation:
Gas evolution is a common indicator of a chemical reaction because it suggests the formation of a new substance.

Q18. The black coating formed on silver articles exposed to air is mainly due to:

A. Silver nitrate
B. Silver sulphide
C. Silver oxide
D. Silver chloride

Answer: B

Explanation:
Silver reacts slowly with sulphur compounds in air to form silver sulphide, which appears as a black layer.

Q19. Which substance undergoes decomposition in the presence of sunlight during black-and-white photography?

A. Silver bromide
B. Sodium chloride
C. Copper sulphate
D. Calcium oxide

Answer: A

Explanation:
Silver bromide decomposes when exposed to light, producing silver metal. This reaction is used in traditional photography.

Q20. The reaction between an acid and a base to form salt and water is called:

A. Decomposition reaction
B. Neutralisation reaction
C. Redox reaction
D. Displacement reaction

Answer: B

Explanation:
In a neutralisation reaction, acids react with bases to produce salt and water, usually releasing heat.

Q21. Which of the following is a balanced chemical equation?

A. H₂ + O₂ → H₂O
B. 2H₂ + O₂ → 2H₂O
C. H₂ + O₂ → 2H₂O
D. H₂ + 2O₂ → H₂O

Answer: B

Explanation:
The equation is balanced because the number of hydrogen and oxygen atoms is equal on both sides of the reaction.

Q22. What is the colour of copper sulphate solution before a displacement reaction with iron?

A. Green
B. Blue
C. Yellow
D. Colourless

Answer: B

Explanation:
Copper sulphate solution has a characteristic blue colour due to the presence of copper ions.

Q23. Which reaction releases heat energy to the surroundings?

A. Endothermic reaction
B. Photolytic reaction
C. Exothermic reaction
D. Electrolytic reaction

Answer: C

Explanation:
Exothermic reactions release energy in the form of heat, light, or sound during the chemical process.

Q24. What is formed when quicklime reacts with water?

A. Calcium carbonate
B. Calcium hydroxide
C. Calcium oxide
D. Calcium chloride

Answer: B

Explanation:
Quicklime reacts vigorously with water to form calcium hydroxide and releases a large amount of heat.

Q25. Which of the following reactions involves exchange of ions between compounds?

A. Combination reaction
B. Double displacement reaction
C. Decomposition reaction
D. Oxidation reaction

Answer: B

Explanation:
In double displacement reactions, ions from two compounds exchange places to form new compounds.

Q26. Rusting of iron requires the presence of:

A. Oxygen only
B. Water only
C. Oxygen and moisture
D. Nitrogen and sunlight

Answer: C

Explanation:
Iron rusts when it comes in contact with both oxygen and water. Moisture accelerates the corrosion process.

Q.27 Which of the following substances is commonly used to prevent oxidation in packaged foods?

A. Catalyst
B. Antioxidant
C. Acid
D. Indicator

Answer: B

Explanation:
Antioxidants slow down oxidation reactions in food products and help prevent spoilage due to rancidity.

Q28. The chemical formula of calcium carbonate is:

A. CaCO₂
B. Ca₂CO₃
C. CaCO₃
D. Ca(CO₃)₂

Answer: C

Explanation:
Calcium carbonate contains one calcium atom, one carbon atom, and three oxygen atoms, represented by CaCO₃.

Q29. Which gas supports combustion and is released during decomposition of potassium chlorate?

A. Nitrogen
B. Hydrogen
C. Oxygen
D. Carbon dioxide

Answer: C

Explanation:
Potassium chlorate decomposes on heating to release oxygen gas, which supports burning.

Q30. A student notices bubbles forming when dilute acid is added to a metal sample. The bubbles most likely contain:

A. Chlorine gas
B. Oxygen gas
C. Hydrogen gas
D. Nitrogen gas

Answer: C

Explanation:
Most metals react with dilute acids to produce hydrogen gas along with a salt. The gas appears as bubbles during the reaction.

What You Will Learn in Chapter 1

This chapter introduces students to the basic concepts of chemical changes and how reactions are represented using equations. It also explains how different types of reactions take place in everyday life.

Important Concepts Covered

• Chemical reactions
• Chemical equations
• Balanced chemical equations
• Combination reactions
• Decomposition reactions
• Displacement reactions
• Double displacement reactions
• Oxidation and reduction
• Corrosion
• Rancidity

How Practising Chapter 1 MCQs

Many students read the chapter properly but still make mistakes in objective questions during exams. Practising MCQs regularly helps in understanding concepts in a much better way.

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