Chemical Reactions and Equations — Class 10 MCQs with Answers
Class 10 CBSE Science (Chemistry) · Chapter 1
90 practice questions · 30 Easy · 30 Medium · 30 Hard · Updated
Practise the most important Class 10 CBSE Science (Chemistry) questions from Chapter 1, "Chemical Reactions and Equations". You get 9 timed quizzes made from 90 NCERT-based MCQs, with answers and explanations. The questions are split into 30 Easy, 30 Medium and 30 Hard. Warm up on the basics, then move on to the exam-level questions that set top scorers in CBSE Board exams and the JEE & NEET foundation years apart.
To score well in "Chemical Reactions and Equations", focus on clear concepts in physics, chemistry and biology basics. Each MCQ here is timed and uses exam-style marking (+4 correct, −1 wrong, 0 skipped). This trains you to stay accurate under time pressure, as real papers need. Every question has a short explanation, so a wrong answer becomes a quick lesson. It is the fastest way to fix gaps before a test.
Use this chapter for focused revision. Start with the Easy set to check your basics on Chemical Reactions and Equations, then move to Medium and Hard to practise applying them. Your accuracy, streaks and XP save automatically. This chapter also adds to your overall Class 10 Science (Chemistry) mastery score. 14 sample questions are solved in full below, with the answer and a worked explanation. Sign in free to start practising.
Key concepts: Chemical Reactions and Equations (Class 10 Science (Chemistry))
A chemical reaction rearranges atoms into new substances, and a balanced equation is the statement that no atom is created or destroyed. This chapter classifies the main reaction types and explains the everyday effects of oxidation — corrosion of metals and rancidity of food.
- Chemical reaction
- A change in which one or more substances are converted into new substances with different properties, signalled by colour change, gas evolution, precipitate or temperature change.
- Chemical equation
- A symbolic representation of a reaction with reactants on the left and products on the right, joined by an arrow showing the direction of change.
- Balancing an equation
- Adjusting coefficients so each element has the same number of atoms on both sides, as required by the law of conservation of mass.
- Law of conservation of mass
- Mass is neither created nor destroyed in a chemical reaction, which is precisely why every equation must be balanced.
Chemical Reactions and Equations — important questions & MCQs with answers (Class 10 Science (Chemistry))
14 solved questions from this chapter's difficulty levels, each with its answer and explanation. The other 76 are timed and scored when you sign in.
- Q1Easy
A balanced chemical equation reflects the law of:
A.Conservation of mass✓ CorrectB.Definite proportionsC.Multiple proportionsD.Conservation of energyAnswer: A. Conservation of mass
Explanation: Balancing ensures atoms of each element are equal on both sides — i.e., mass is conserved.
- Q2Easy
CaO + H₂O → Ca(OH)₂ is an example of:
A.Decomposition reactionB.Combination reaction✓ CorrectC.Displacement reactionD.Double displacement reactionAnswer: B. Combination reaction
Explanation: Two reactants combine to form a single product — combination reaction.
- Q3Easy
Oxidation involves:
A.Only addition of metalsB.Gain of hydrogen / loss of oxygenC.No change in atomsD.Loss of hydrogen / gain of oxygen✓ CorrectAnswer: D. Loss of hydrogen / gain of oxygen
Explanation: Oxidation = gain of O / loss of H (or loss of electrons in modern terms).
- Q4Easy
A reaction in which two or more substances combine to form a single product is called:
A.DisplacementB.DecompositionC.Combination✓ CorrectD.Double displacementAnswer: C. Combination
Explanation: A combination reaction joins two or more reactants into a single product, A + B → AB — the reverse of decomposition, where one reactant splits into several products.
- Q5Easy
Rusting of iron produces:
A.Iron chlorideB.Iron sulphateC.Iron carbonateD.Hydrated iron(III) oxide✓ CorrectAnswer: D. Hydrated iron(III) oxide
Explanation: Iron reacts with oxygen and moisture in air to form a hydrated iron(III) oxide, Fe₂O₃·xH₂O — rust — not a chloride, sulphate or carbonate salt.
- Q6Easy
Rancidity of food is caused by:
A.ReductionB.Oxidation of fats and oils✓ CorrectC.NeutralisationD.SublimationAnswer: B. Oxidation of fats and oils
Explanation: Fats and oils react slowly with atmospheric oxygen; this slow oxidation changes their smell and taste, which is the rancidity that spoils stored fatty foods.
- Q7Medium
Balance: Fe + H₂O → Fe₃O₄ + H₂. The coefficients (in order) are:
A.1, 4, 3, 4B.3, 4, 1, 4✓ CorrectC.3, 4, 1, 1D.1, 1, 1, 1Answer: B. 3, 4, 1, 4
Explanation: 3Fe + 4H₂O → Fe₃O₄ + 4H₂. Check: 3 Fe, 8 H, 4 O on each side.
- Q8Medium
Zn + CuSO₄ → ZnSO₄ + Cu is an example of:
A.Displacement✓ CorrectB.DecompositionC.CombinationD.CombustionAnswer: A. Displacement
Explanation: Zinc is more reactive than copper and displaces it from the salt — displacement reaction.
- Q9Medium
In 2 Cu + O₂ → 2 CuO, Cu is:
A.Reduced and oxidisedB.ReducedC.Oxidised✓ CorrectD.UnchangedAnswer: C. Oxidised
Explanation: Copper combines with oxygen from air on heating to form copper oxide, 2Cu + O₂ → 2CuO, so copper gains oxygen and is oxidised.
- Q10Medium
On heating, CaCO₃ decomposes to give:
A.CaO + CO₂✓ CorrectB.CaO + COC.Ca + CO₂D.Ca + C + O₂Answer: A. CaO + CO₂
Explanation: Strong heating breaks calcium carbonate down into calcium oxide (quicklime) and carbon dioxide gas — a thermal decomposition, CaCO₃ → CaO + CO₂.
- Q11Medium
Aluminium does not corrode further after a thin layer forms because:
A.Al has no oxideB.Al is too reactiveC.A protective oxide layer prevents further reaction✓ CorrectD.Al is unreactiveAnswer: C. A protective oxide layer prevents further reaction
Explanation: Aluminium reacts with air to form a thin, tightly-adhering layer of Al₂O₃ that seals the metal beneath from further oxygen contact, halting corrosion.
- Q12Hard
Balanced form of MnO₂ + HCl → MnCl₂ + Cl₂ + H₂O uses HCl coefficient:
A.6B.2C.4✓ CorrectD.8Answer: C. 4
Explanation: Balancing this redox reaction needs 4 HCl to supply the four Cl atoms split between MnCl₂ and Cl₂, and four H atoms for the two water molecules formed.
- Q13Hard
Which of the following reactions is endothermic?
A.Burning of natural gasB.Respiration in cellsC.Photosynthesis✓ CorrectD.Slaking of lime (CaO + H₂O)Answer: C. Photosynthesis
Explanation: Photosynthesis absorbs sunlight (energy taken IN) — endothermic. The others release heat.
- Q14Hard
In the reaction CuO + H₂ → Cu + H₂O, the substance reduced is:
A.H₂B.CuO✓ CorrectC.CuD.H₂OAnswer: B. CuO
Explanation: CuO loses oxygen → reduction. H₂ gains oxygen → oxidation.
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Start this chapter free →Chemical Reactions and Equations — FAQs
What are the key concepts in Class 10 Science (Chemistry) Chemical Reactions and Equations?+
A chemical reaction rearranges atoms into new substances, and a balanced equation is the statement that no atom is created or destroyed. This chapter classifies the main reaction types and explains the everyday effects of oxidation — corrosion of metals and rancidity of food. Key ideas include Chemical reaction, Chemical equation, Balancing an equation, Law of conservation of mass.
What does Class 10 Science (Chemistry) Chapter 1 (Chemical Reactions and Equations) cover on XamBaaz?+
It has 90 NCERT-based MCQs on "Chemical Reactions and Equations": 30 Easy, 30 Medium and 30 Hard. Together they make 9 timed quizzes, and you never get the same set twice. Every question has an instant explanation. They help you prepare for CBSE Board exams and the JEE & NEET foundation years.
Are these "Chemical Reactions and Equations" questions free to practise?+
Yes. Sign in with Google to practise "Chemical Reactions and Equations" free. Full unlimited access is ₹999/year on a launch offer until 1 December 2026. No chapter is charged separately.
How should I revise "Chemical Reactions and Equations" for the exam?+
Start with the Easy quiz to check your basics, then try Medium and Hard to practise applying them. There are 9 timed quizzes on this chapter, so you can come back for a fresh set instead of one you have seen. Read each explanation, retry the questions you miss, and track your accuracy until it stays high.
Are these "Chemical Reactions and Equations" MCQs available with answers?+
Yes. 14 sample questions are shown here in full, each with the correct option and a step-by-step "Why" explanation. Sign in free with Google to start practising, with instant scoring.
Is there negative marking in the "Chemical Reactions and Equations" quizzes?+
Yes. The timed quizzes use exam-style marking: +4 for a right answer, −1 for a wrong one and 0 for a skip. MHT-CET and CBSE board papers have no negative marking. Our mocks for those are scored their way.
What are the important questions from Chemical Reactions and Equations (Class 10 Science (Chemistry))?+
The questions that matter most test Chemical reaction, Chemical equation, Balancing an equation, Law of conservation of mass. This page shows 14 solved important MCQs with answers and explanations; all 90 questions on the chapter are available as timed quizzes once you sign in.
Is there an online quiz for Chemical Reactions and Equations?+
Yes — Class 10 Science (Chemistry) Chemical Reactions and Equations has timed online quizzes at Easy, Medium and Hard levels, with instant scoring and a worked explanation on every question. The first quiz on the chapter is free.