Chemical Reactions Exemplar — Class 10 Science NCERT Solutions (Free)
Free step-by-step NCERT solutions for Class 10 Science chapter "Chemical Reactions Exemplar" — 5 important questions with detailed answers for CBSE board exam preparation.
TL;DR: Free step-by-step NCERT solutions for Class 10 Science chapter "Chemical Reactions Exemplar" — 5 important questions with detailed answers for CBSE bo…
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NCERT Solutions for Class 10 Science — Chemical Reactions Exemplar. Step-by-step answers to all 5 textbook questions from this chapter, written for CBSE board preparation and free to use.
Chemical Reactions Exemplar — All 5 Questions Solved
Q1. What is a chemical reaction? Classify the reaction: 2H2 + O2 → 2H2O.
Chemical reaction is transformation of substances resulting in formation of new substances with different properties. The reaction 2H2 + O2 → 2H2O is a combination reaction (two or more reactants combine to form one product). It is also an exothermic reaction (heat is released).
Q2. Distinguish between displacement and double displacement reactions.
Displacement reaction: A + BC → AC + B (one element displaces another). Example: Fe + CuSO4 → FeSO4 + Cu. Double displacement: AB + CD → AD + CB (two compounds exchange ions). Example: AgNO3 + NaCl → AgCl (ppt) + NaNO3.
Q3. Balance the chemical equation: Fe + Cl2 → FeCl3.
Iron has 3 electrons in valence, chlorine takes 1. So Fe forms FeCl3. Left: 1 Fe, 2 Cl. Right: 1 Fe, 3 Cl. Balance: 2Fe + 3Cl2 → 2FeCl3.
Q4. What is decomposition reaction? Give one example.
Decomposition reaction is breaking down of one compound into two or more simpler substances. Example: 2H2O → 2H2 + O2 (when electricity is passed, electrolytic decomposition). Another: CaCO3 → CaO + CO2 (thermal decomposition).
Q5. Write balanced equation for combustion of methane and classify it.
CH4 + 2O2 → CO2 + 2H2O. Combustion is a reaction where a substance burns in oxygen, releasing heat and light. This is exothermic (heat releasing) and oxidation-reduction (redox) reaction.
How to Use These Solutions
Attempt each question yourself first and only then compare with the worked answer. Marks in the CBSE board exam are awarded for the METHOD as much as the final result, so reproduce the steps rather than memorising the last line. Where a solution states a law, a formula or a definition, learn that wording — examiners look for it.
Related practice for this chapter: chapter MCQs, previous-year questions, revision notes and sample papers.