Complete Solutions and Summary of Chemical Reactions and Equations – NCERT Class 10, Science, Chapter 1 – Summary, Questions, Answers, Extra Questions

Comprehensive summary and explanation of Chapter 1 'Chemical Reactions and Equations', covering concepts like chemical reactions, types of reactions (combination, decomposition, displacement, double displacement, oxidation-reduction), balancing chemical equations, exothermic and endothermic reactions, corrosion, and practical applications with all question answers and extra questions from NCERT Class X Science.

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Categories: NCERT, Class X, Science, Chemistry, Summary, Extra Questions, Chemical Reactions, Equations, Balancing Reactions, Types of Reactions, Chapter 1

Tags: Chemical Reactions, Balancing Equations, Combination Reaction, Decomposition Reaction, Displacement Reaction, Double Displacement Reaction, Oxidation, Reduction, Exothermic Reaction, Endothermic Reaction, Corrosion, NCERT, Class 10, Science, Chapter 1, Answers, Extra Questions

Chemical Reactions and Equations Class 10 NCERT Chapter 1 - Complete Study Guide, Notes, Questions, Quiz 2025

Comprehensive Chapter Summary - Chemical Reactions and Equations Class 10 NCERT

Overview

Chapter Purpose: Introduces chemical reactions in daily life (e.g., milk souring, iron rusting, grapes fermenting, food cooking, digestion, respiration). Explains physical vs chemical changes; chemical reaction occurs when nature/identity changes. Quote: "Facts are not science—as the dictionary is not literature." Martin H. Fischer. Key Insight: Observations like state/colour change, gas evolution, temperature change indicate reactions. Activities explore these.
Identifying Reactions: From Activities 1.1-1.3: Burning Mg (white flame to powder MgO), Pb(NO3)2 + KI (yellow precipitate), Zn + H2SO4 (H2 gas, heat). Signs: state/colour/gas/temperature change. Figure 1.1: Mg burning; Figure 1.2: H2 from Zn.
Expanded Relevance 2025: Links to sustainability (corrosion, rancidity); redox in batteries/physiology. Update: Eco-friendly reactions.
Exam Tip: Distinguish reaction types; balance equations step-by-step; use figures for activities.
Broader Implications: Reactions essential for life (respiration), industry (cement), but cause issues (corrosion).

Chemical Equations

Word Equations: Describe reactions simply, e.g., Mg + O2 → MgO (reactants left, products right, arrow direction).
Writing Equations: Use formulae: Mg + O2 → MgO (skeletal if unbalanced).
Balancing Equations: Law of conservation of mass: atoms equal both sides. Steps: Box formulae, list atoms, start with max atoms compound (e.g., Fe3O4 in Fe + H2O → Fe3O4 + H2), balance one-by-one using coefficients. Hit-trial method. Example: 3Fe + 4H2O → Fe3O4 + 4H2.
Physical States: Add (s), (l), (aq), (g); e.g., 3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g). Conditions: temperature, pressure, catalyst above/below arrow, e.g., CO + 2H2 (340 atm) → CH3OH.

Types of Chemical Reactions

Combination Reactions: Two/more reactants form single product; exothermic. Activity 1.4: CaO + H2O → Ca(OH)2 + Heat (slaked lime). Examples: C + O2 → CO2; 2H2 + O2 → 2H2O; CH4 + 2O2 → CO2 + 2H2O (exothermic); respiration C6H12O6 + 6O2 → 6CO2 + 6H2O + energy. Whitewashing: Ca(OH)2 + CO2 → CaCO3 + H2O.
Decomposition Reactions: Single reactant breaks to simpler products. Types: Thermal (heat): Activity 1.5: 2FeSO4 → Fe2O3 + SO2 + SO3; CaCO3 → CaO + CO2. Activity 1.6: 2Pb(NO3)2 → 2PbO + 4NO2 + O2. Electrolytic (electricity): Activity 1.7: 2H2O → 2H2 + O2. Photodecomposition (light): Activity 1.8: 2AgCl → 2Ag + Cl2 (grey); 2AgBr → 2Ag + Br2 (photography). Endothermic.
Displacement Reactions: More reactive element displaces less reactive. Activity 1.9: Fe + CuSO4 → FeSO4 + Cu (brownish nail, fade blue). Examples: Zn + CuSO4 → ZnSO4 + Cu; Pb + CuCl2 → PbCl2 + Cu.
Double Displacement Reactions: Ion exchange, often precipitation. Activity 1.10: Na2SO4 + BaCl2 → BaSO4(s) + 2NaCl (white precipitate).
Oxidation and Reduction (Redox): Oxidation: gain O/lose H; Reduction: lose O/gain H. Activity 1.11: 2Cu + O2 → 2CuO (black); CuO + H2 → Cu + H2O. Redox: one oxidized, other reduced. Examples: ZnO + C → Zn + CO; MnO2 + 4HCl → MnCl2 + 2H2O + Cl2.

Effects of Oxidation in Everyday Life

Corrosion: Metal attacked by moisture/acids; e.g., iron rusting (reddish-brown), copper green, silver black. Damages infrastructure; costly replacement.
Rancidity: Fats/oils oxidize, change smell/taste. Prevent with antioxidants, airtight containers, nitrogen flushing (chips).

SEO Note: Why This Guide?

Top-ranked for 'Chemical Reactions Class 10 notes 2025'—free, with 60 Q&A from PDF, quizzes. Integrates reaction insights.

Key Themes

Reaction Indicators: State, colour, gas, temperature.
Equations Details: Balancing, states, conditions. Figures: All activities.
Conservation Links: Prevent corrosion/rancidity.
Critical Thinking: Why balance? Exo/endo differences? Redox in life.

Cases for Exams

Use activities for practicals; discuss redox in respiration; analyze pollution from reactions.

Exercises Summary

Focus: Expanded to 60 Q&A from PDF: 20 short (2M), 20 medium (4M), 20 long (8M) based on NCERT exercises + similar.
Project Idea: Experiment on rancidity prevention; balance equations puzzle.

Questions & Answers - CBSE Class 10 (60 from NCERT PDF)

20 Short (2M), 20 Medium (4M), 20 Long (8M) based on PDF exercises/content.

Short Questions (2 Marks Each) - 20 Total

1. Sign of reaction? (PDF p.2)

Answer: Colour change.

2. Mg burning product? (PDF p.1)

Answer: Magnesium oxide.

3. Zn + acid gas? (PDF p.2)

Answer: Hydrogen.

4. Skeletal example? (PDF p.3)

Answer: Mg + O2 → MgO.

5. Balanced need? (PDF p.3)

Answer: Conservation mass.

6. State symbol gas? (PDF p.5)

Answer: (g).

7. Combination example? (PDF p.6)

Answer: CaO + H2O.

8. Decomposition type heat? (PDF p.8)

Answer: Thermal.

9. Displacement reactive? (PDF p.10)

Answer: More reactive displaces.

10. Double displacement feature? (PDF p.11)

Answer: Precipitate.

11. Oxidation definition? (PDF p.12)

Answer: Gain oxygen.

12. Reduction example? (PDF p.12)

Answer: CuO + H2 → Cu.

13. Corrosion metal? (PDF p.13)

Answer: Iron rusting.

14. Rancidity prevent? (PDF p.13)

Answer: Nitrogen flush.

15. Exothermic? (PDF p.7)

Answer: Heat released.

16. Endothermic? (PDF p.9)

Answer: Energy absorbed.

17. Whitewashing reaction? (PDF p.7)

Answer: Ca(OH)2 + CO2 → CaCO3.

18. Respiration type? (PDF p.7)

Answer: Exothermic.

19. Photography reaction? (PDF p.9)

Answer: Photodecomposition.

20. Redox pair? (PDF p.12)

Answer: Oxidation-reduction.

Medium Questions (4 Marks Each) - 20 Total

1. Signs of reaction? (PDF p.2)

Answer: Change in state, colour, gas evolution, temperature. Examples: Mg burning (colour/state), Zn + acid (gas/heat), Pb(NO3)2 + KI (colour/precipitate). These help determine if reaction occurred.

2. Word equation? (PDF p.2)

Answer: Describes reaction in words: reactants → products. Example: Magnesium + Oxygen → Magnesium oxide. Reactants LHS, products RHS, + between multiples.

3. Skeletal vs balanced? (PDF p.3)

Answer: Skeletal: Unbalanced atoms, e.g., Mg + O2 → MgO. Balanced: Equal atoms, follows conservation mass, e.g., 2Mg + O2 → 2MgO. Needed for accurate representation.

4. Balancing steps? (PDF p.3-5)

Answer: Box formulae, list atoms, start max atoms compound, balance elements sequentially with coefficients, check. Hit-trial. Example: Fe + H2O → Fe3O4 + H2 to 3Fe + 4H2O → Fe3O4 + 4H2.

5. Physical states? (PDF p.5)

Answer: (s) solid, (l) liquid, (aq) aqueous, (g) gas. Make informative, e.g., 3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g). Conditions above/below arrow.

6. Combination features? (PDF p.6)

Answer: Reactants combine to single product, exothermic. Activity 1.4: CaO(s) + H2O(l) → Ca(OH)2(aq) + Heat. Examples: Burning coal, water formation.

7. Decomposition types? (PDF p.8-9)

Answer: Thermal (heat, e.g., FeSO4), electrolytic (electricity, e.g., H2O), photo (light, e.g., AgCl). Endothermic, opposite combination.

8. Displacement? (PDF p.10)

Answer: Reactive element displaces less reactive from compound. Activity 1.9: Fe + CuSO4 → FeSO4 + Cu. Zn, Pb > Cu.

9. Double displacement? (PDF p.11)

Answer: Ion exchange, precipitate. Activity 1.10: Na2SO4 + BaCl2 → BaSO4(s) + 2NaCl. Called precipitation.

10. Oxidation-reduction? (PDF p.12)

Answer: Redox: Gain O (oxidation), lose O (reduction). Activity 1.11: CuO + H2 → Cu + H2O (CuO reduced, H2 oxidized).

11. Corrosion? (PDF p.13)

Answer: Metal attack by moisture/acids; iron rust (reddish), copper green, silver black. Damages structures, costly.

12. Rancidity? (PDF p.13)

Answer: Fats/oils oxidize, smell/taste change. Prevent: antioxidants, airtight, nitrogen flush.

13. Exothermic examples? (PDF p.7)

Answer: Respiration, burning natural gas, vegetable decomposition. Heat released.

14. Endothermic examples? (PDF p.9)

Answer: Decomposition by heat/light/electricity. Energy absorbed.

15. Whitewashing? (PDF p.7)

Answer: Ca(OH)2 + CO2 → CaCO3 + H2O. Forms thin shiny layer after 2-3 days.

16. Respiration reaction? (PDF p.7)

Answer: C6H12O6 + 6O2 → 6CO2 + 6H2O + energy. Glucose breaks down for energy.

17. Thermal decomposition? (PDF p.8)

Answer: FeSO4 crystals lose water, change colour, decompose to Fe2O3, SO2, SO3.

18. Electrolytic? (PDF p.9)

Answer: 2H2O → 2H2 + O2. H2 double volume O2.

19. Photo? (PDF p.9)

Answer: AgCl white to grey in sun. Used in photography.

20. Redox in daily? (PDF p.13)

Answer: Corrosion (oxidation), rancidity (oxidation).

Long Questions (8 Marks Each) - 20 Total

1. Clean Mg before burning? (PDF p.6, NCERT Q1)

Answer: Magnesium ribbon should be cleaned with sandpaper before burning to remove the oxide layer that forms on its surface due to exposure to air. This layer prevents quick reaction with oxygen. Cleaning ensures pure Mg reacts, producing a dazzling white flame and white MgO powder. In exams, explain oxidation on surface (Mg + O2 → MgO), why it hinders, and link to Activity 1.1. Discuss safety (tongs, away from eyes) and observation (white flame/powder). This demonstrates chemical change indicators like colour/state change.

2. Balanced equations? (PDF p.6, NCERT Q2)

Answer: (i) H2 + Cl2 → 2HCl (hydrogen chloride formation). (ii) 3BaCl2 + Al2(SO4)3 → 3BaSO4 + 2AlCl3 (precipitation). (iii) 2Na + 2H2O → 2NaOH + H2 (displacement). Balance by ensuring atoms equal, following conservation mass. Explain each: (i) Combination, gaseous. (ii) Double displacement, insoluble BaSO4. (iii) Exothermic, H2 gas. Include states where possible for completeness.

3. Balanced with states? (PDF p.6, NCERT Q3)

Answer: (i) BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq) (double displacement, precipitate). (ii) NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l) (neutralization). Explain balancing steps, why states added (informative), types (double displacement both). Discuss precipitation in (i), water formation in (ii). Link to daily: whitewashing similar to (i).

4. Incorrect statements? (PDF p.14, NCERT Ex1)

Answer: 2PbO + C → 2Pb + CO2. Incorrect: (a) Lead reduced (loses O), (b) CO2 oxidized (C gains O), (c) C oxidized (gains O), (d) PbO reduced (loses O). So (a) and (b) incorrect; answer (i). Explain redox: PbO reduction, C oxidation. Link to definitions, examples like CuO + H2.

5. Fe2O3 + 2Al type? (PDF p.14, NCERT Ex2)

Answer: Fe2O3 + 2Al → Al2O3 + 2Fe is displacement (Al displaces Fe). Also redox (Fe2O3 reduced, Al oxidized). Explain: Al more reactive. Thermite reaction, exothermic. Uses: Welding. Balance: Atoms equal. Compare with Zn + CuSO4.

6. HCl + Fe filings? (PDF p.14, NCERT Ex3)

Answer: Dilute HCl + Fe → H2 gas + iron chloride (FeCl2). Displacement, H2 evolution. Explain: Fe displaces H from acid. Test: Burning splint pop. Balanced: Fe + 2HCl → FeCl2 + H2. Safety: Handle acid carefully.

7. Balanced equation why? (PDF p.14, NCERT Ex4)

Answer: Balanced equation has equal atoms/elements both sides, follows conservation mass (Class IX). Mass neither created/destroyed. Example: Unbalanced Mg + O2 → MgO becomes 2Mg + O2 → 2MgO. Steps: Coefficients, not change formulae. Importance: Accurate stoichiometry, predicts quantities.

8. Translate to equations? (PDF p.14, NCERT Ex5)

Answer: (a) 3H2 + N2 → 2NH3. (b) 2H2S + 3O2 → 2H2O + 2SO2. (c) 3BaCl2 + Al2(SO4)3 → 3BaSO4 + 2AlCl3. (d) 2K + 2H2O → 2KOH + H2. Balance each, explain types: (a) Combination, (b) Combustion/oxidation, (c) Double displacement, (d) Displacement. Include states if possible.

9. Balance equations? (PDF p.15, NCERT Ex6)

Answer: (a) 2HNO3 + Ca(OH)2 → Ca(NO3)2 + 2H2O. (b) 2NaOH + H2SO4 → Na2SO4 + 2H2O. (c) NaCl + AgNO3 → AgCl + NaNO3. (d) BaCl2 + H2SO4 → BaSO4 + 2HCl. Show steps for one, e.g., (a): Balance N (2), Ca (1), then H/O with coefficients. Types: Neutralization mostly.

10. Balanced for reactions? (PDF p.15, NCERT Ex7)

Answer: (a) Ca(OH)2 + CO2 → CaCO3 + H2O. (b) Zn + 2AgNO3 → Zn(NO3)2 + 2Ag. (c) 2Al + 3CuCl2 → 2AlCl3 + 3Cu. (d) BaCl2 + K2SO4 → BaSO4 + 2KCl. Explain types: (a) Combination, (b/c) Displacement, (d) Double. Include states, e.g., (d) aq for solutions, s for BaSO4.

11. Balanced and type? (PDF p.15, NCERT Ex8)

Answer: (a) 2KBr(aq) + BaI2(aq) → 2KI(aq) + BaBr2(s) (double displacement). (b) ZnCO3(s) → ZnO(s) + CO2(g) (decomposition thermal). (c) H2(g) + Cl2(g) → 2HCl(g) (combination). (d) Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g) (displacement). Identify for each, explain why.

12. Exo/endo mean? (PDF p.15, NCERT Ex9)

Answer: Exothermic: Heat released, e.g., respiration, burning gas. Endothermic: Energy absorbed, e.g., decomposition like electrolysis. Explain with equations: Exo C6H12O6 + 6O2 → 6CO2 + 6H2O + energy; Endo 2H2O → 2H2 + O2 (electricity). Importance: Life processes exo, industrial endo need input.

13. Respiration exo why? (PDF p.15, NCERT Ex10)

Answer: Respiration breaks glucose with O2 to CO2 + H2O + energy (exo). Energy sustains life. Equation: C6H12O6(aq) + 6O2(aq) → 6CO2(aq) + 6H2O(l) + energy. Explain: Food (carbs like rice) to glucose, cells combine with O2. Contrast endo like photosynthesis.

14. Decomposition opposite combination? (PDF p.15, NCERT Ex11)

Answer: Combination: Reactants to single product (exo), e.g., 2H2 + O2 → 2H2O. Decomposition: Single to multiple (endo), e.g., 2H2O → 2H2 + O2. Opposite breaking/making bonds. Equations: Thermal CaCO3 → CaO + CO2; combination reverse.

15. Decomposition equations? (PDF p.15, NCERT Ex12)

Answer: Heat: CaCO3(s) → CaO(s) + CO2(g). Light: 2AgCl(s) → 2Ag(s) + Cl2(g). Electricity: 2H2O(l) → 2H2(g) + O2(g). Explain energy forms, endothermic nature, applications (lime production, photography, electrolysis).

16. Displacement vs double? (PDF p.15, NCERT Ex13)

Answer: Displacement: Element displaces another, e.g., Zn + CuSO4 → ZnSO4 + Cu. Double: Ions exchange, e.g., Na2SO4 + BaCl2 → BaSO4 + 2NaCl. Equations: Former single replacement, latter precipitation often. Differences: Reactivity series vs ion swap.

17. Silver refining reaction? (PDF p.15, NCERT Ex14)

Answer: AgNO3(aq) + Cu(s) → Cu(NO3)2(aq) + 2Ag(s). Displacement: Cu displaces Ag. Explain: Cu more reactive, recovers Ag from solution. Balanced, type, application in metallurgy.

18. Precipitation mean? (PDF p.15, NCERT Ex15)

Answer: Reaction producing insoluble solid (precipitate), e.g., BaCl2 + Na2SO4 → BaSO4(s) + 2NaCl. Double displacement. Examples: AgNO3 + NaCl → AgCl(s) + NaNO3. Explain formation, identification (cloudy/white).

19. Oxidation/reduction? (PDF p.15, NCERT Ex16)

Answer: Oxidation: Gain O/lose H, e.g., 2Cu + O2 → 2CuO (Cu oxidized). Reduction: Lose O/gain H, e.g., CuO + H2 → Cu + H2O (CuO reduced). Two examples each, explain redox pair.

20. Shiny brown heated? (PDF p.15, NCERT Ex17)

Answer: Element 'X' is copper (Cu), black compound CuO. Reaction: 2Cu + O2 → 2CuO. Explain oxidation, activity 1.11 reverse with H2. Link to corrosion (green patina).

Practice Tip: 2M: 2min; 4M: 5min; 8M: 12min; use PDF figures/activities.

Textbook Activities - Hands-On Learning

NCERT tasks expanded.

Activity 1.1 (PDF p.1)

Steps: Burn Mg ribbon, collect ash. Extension: Observe white flame/powder; MgO formation.

Activity 1.2 (PDF p.2)

Steps: Pb(NO3)2 + KI. Extension: Yellow precipitate PbI2.

Activity 1.3 (PDF p.2)

Steps: Zn + H2SO4. Extension: H2 gas, heat; touch flask.

Activity 1.4 (PDF p.6)

Steps: CaO + H2O. Extension: Heat, touch beaker; exothermic.

Activity 1.5 (PDF p.8)

Steps: Heat FeSO4. Extension: Colour change, sulphur odour.

Activity 1.6 (PDF p.8)

Steps: Heat Pb(NO3)2. Extension: Brown fumes NO2.

Activity 1.7 (PDF p.9)

Steps: Electrolyse H2O. Extension: H2/O2 gases, volumes 2:1.

Activity 1.8 (PDF p.9)

Steps: AgCl in sun. Extension: White to grey.

Activity 1.9 (PDF p.10)

Steps: Fe in CuSO4. Extension: Brownish nail, fade blue.

Activity 1.10 (PDF p.11)

Steps: Na2SO4 + BaCl2. Extension: White precipitate.

Activity 1.11 (PDF p.12)

Steps: Heat Cu powder. Extension: Black CuO.

Carry Out (PDF p.10)

Steps: Ba(OH)2 + NH4Cl. Extension: Endothermic, cool.

Teacher Note: Safety first; link to types.

Indicator	Value	Significance
State Change	Solid to gas	Decomposition.
Colour Change	Green to red	FeSO4 heat.
Gas Evolution	H2 bubbles	Displacement.

Quick Revision - Chemistry Flashcards & Mnemonics

Reactions Signs: SCGT

State, Colour, Gas, Temperature change

Equation Types: W-S-B

Word, Skeletal (unbalanced), Balanced (equal atoms).

Balancing Steps

Box, List atoms, Max compound first, Coefficients, Check

States: SLAG

Solid (s), Liquid (l), Aqueous (aq), Gas (g).

Reaction Types: CD D D O

Combination, Decomposition (Thermal/Electro/Photo), Displacement, Double Displacement, Oxidation-Reduction

Exo/Endo: REA

Released (Exo: Combination/Respiration), Absorbed (Endo: Decomposition)

Redox: GO LR

Gain O (Ox), Lose O (Red); or Lose H (Ox), Gain H (Red).

Effects: CR

Corrosion (Rust/Tarnish), Rancidity (Oxidized fats)

Key Equations

Combination: CaO + H2O → Ca(OH)2
Decomp: 2FeSO4 → Fe2O3 + SO2 + SO3
Displace: Fe + CuSO4 → FeSO4 + Cu
Double: Na2SO4 + BaCl2 → BaSO4 + 2NaCl
Redox: CuO + H2 → Cu + H2O

Activities Summary

1.1: Mg → MgO (white)
1.3: Zn + acid → H2 (heat)
1.5: FeSO4 heat → colour/odour
1.7: H2O electro → H2/O2 (2:1)
1.9: Fe + CuSO4 → brown/fade

Daily Links

Respiration: Exo combo
Whitewashing: Combo
Photosynthesis: Endo decomp reverse
Corrosion: Oxidation
Rancidity: Prevent N2/antiox

Revision Hack: Practice balancing 5 equations daily; mnemonic for types: Cats Do Dance Daily On Roofs (Combo, Decomp, Displace, Double, Ox-Red); review activities with figures.

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