Important questions for Class 10 Science Chapter 1 are a focused set of exam-ready questions covering Chemical Reactions and Equations. This chapter introduces students to how chemical reactions are represented, balanced, and classified from combination and decomposition to redox reactions, corrosion, and rancidity.
Chemical Reactions and Equations explains how reactions are written, balanced, and classified. Students also learn oxidation, reduction, corrosion, and rancidity in this chapter. Board exams ask direct, application-based, and equation-writing questions from this unit. That is why this chapter is one of the highest-value scoring chapters in Class 10 Science.
CBSE Class 10 Science Chapter 1 important Question & Answers
Q.
Which of the statements about the reaction below are incorrect?
2PbO(s) + C(s) →2Pb(s) + CO2(g)
(a) Lead is getting reduced.
(b) Carbon dioxide is getting oxidised.
(c) Carbon is getting oxidised.
(d) Lead oxide is getting reduced.
(i) (a) and (b)
(ii) (a) and (c)
(iii) (a), (b) and (c)
(iv) all
Q.
Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.
Q.
Oil and fat containing food items are flushed with nitrogen. Why?
Q.
Why do we apply paint on iron articles?
Q.
A shiny brown coloured element ‘X’ on heating in air becomes black in colour.
Name the element ‘X’ and the black coloured compound formed.
Q.
Explain the following in terms of gain or loss of oxygen with two examples each.
(a) Oxidation
(b) Reduction
Q.
What do you mean by a precipitation reaction? Explain by giving examples.
Q.
In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.
Q.
What is the difference between displacement and double displacement reactions? Write equations for these reactions.
Q.
Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.
Q.
Fe2O3+ 2Al →Al2O3+ 2Fe
The above reaction is an example of a
(a) combination reaction.
(b) double displacement reaction
(c) decomposition reaction.
(d) displacement reaction.
Q.
Why is respiration considered an exothermic reaction? Explain.
Q.
What does one mean by exothermic and endothermic reactions? Give examples.
Q.
Write the balanced chemical equation for the following and identify the type of reaction in each case.
(a) Potassium bromide(aq) + Barium iodide(aq) → Potassium iodide(aq) + Barium bromide(s)
(b) Zinc carbonate(s) → Zinc oxide(s) + Carbon dioxide(g)
(c) Hydrogen(g) + Chlorine(g) → Hydrogen chloride(g)
(d) Magnesium(s) + Hydrochloric acid(aq) → Magnesium chloride(aq) + Hydrogen(g)
Q.
Write the balanced chemical equations for the following reactions.
(a) Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water
(b) Zinc + Silver nitrate → Zinc nitrate + Silver
(c) Aluminium + Copper chloride → Aluminium chloride + Copper
(d) Barium chloride + Potassium sulphate → Barium sulphate + Potassium chloride
Q.
Balance the following chemical equations.
(a) HNO3 + Ca(OH)2 → Ca(NO3)2+ H2O
(b) NaOH + H2SO4 → Na2SO4+ H2O
(c) NaCl + AgNO3 → AgCl + NaNO3
(d) BaCl2+ H2SO4 → BaSO4+ HCl
Q.
Translate the following statements into chemical equations and then balance them.
(a) Hydrogen gas combines with nitrogen to form ammonia.
(b) Hydrogen sulphide gas burns in air to give water and sulpur dioxide.
(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.
Q.
What is a balanced chemical equation? Why should chemical equations be balanced?
Q.
What happens when dilute hydrochloric acid is added to iron fillings? Tick the correct answer.
(a) Hydrogen gas and iron chloride are produced.
(b) Chlorine gas and iron hydroxide are produced.
(c) No reaction takes place.
(d) Iron salt and water are produced.
Q.
Explain the following terms with one example each.
(a) Corrosion
(b) Rancidity
This page gives you topic-wise important questions with answers, MCQs, short and long answer questions, PYQs, and common mistake guidance.
Key Takeaways
- Important questions for Class 10 Science Chapter 1 cover all topics from the NCERT chapter like chemical equations, reaction types, oxidation-reduction, corrosion, and rancidity
- Questions are organised by type: MCQs, 1-mark, 2-mark, 3-mark, and 5-mark
- All answers follow the NCERT Reprint 2026-27 version of the chapter
- PYQ-style questions are included separately for targeted board prep
- A Common Mistakes section helps you avoid errors that cost marks
Class 10 Science Chapter 1: What to Focus On
Focus first on balanced equations, reaction types, and oxidation-reduction. Then revise corrosion, rancidity, and NCERT-based examples because these appear often in board papers.
| Topic |
What to Know |
Common Board Question Type |
| Chemical Equations |
Writing, balancing, state symbols |
2-mark balancing, 3-mark write and explain |
| Combination Reaction |
Single product from two reactants |
1-mark identify, 2-mark example |
| Decomposition Reaction |
Thermal, electrolytic, photolytic |
3-mark with equations |
| Displacement Reaction |
More reactive element displaces less reactive |
2-mark identify and explain |
| Double Displacement |
Ion exchange, precipitation |
2-mark with equation |
| Oxidation and Reduction |
Gain/loss of oxygen or hydrogen |
3-mark identify oxidised/reduced substance |
| Corrosion |
Rusting of iron, prevention |
2-mark define and prevent |
| Rancidity |
Oxidation of fats and oils |
1-mark or 2-mark define and prevent |
Important Topics in Class 10 Science Chapter 1
Class 10 Science Chapter 1 important questions usually come from ten core topics. These are chemical equations, balancing, combination, decomposition, displacement, double displacement, oxidation, reduction, corrosion, and rancidity.
Students searching for class 10 science chapter 1 important questions should revise these topics in the NCERT order. That makes the chapter easier to remember and practise.
CBSE Class 10 Science Important Questions
Chemical Equations and Balanced Chemical Equations: Important Questions
Balancing chemical equations tests the Law of Conservation of Mass. Every atom on the left must match the right side.
Q1. What is a balanced chemical equation? Why should chemical equations be balanced? Ans: A balanced chemical equation has equal numbers of atoms of each element on both sides of the arrow. Chemical equations must be balanced to follow the Law of Conservation of Mass, which states that mass can neither be created nor destroyed in a chemical reaction.
Q2. Balance the following chemical equations:
- HNO₃ + Ca(OH)₂ → Ca(NO₃)₂ + H₂O Ans: 2HNO₃ + Ca(OH)₂ → Ca(NO₃)₂ + 2H₂O
- NaOH + H₂SO₄ → Na₂SO₄ + H₂O Ans: 2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O
- NaCl + AgNO₃ → AgCl + NaNO₃ Ans: NaCl + AgNO₃ → AgCl + NaNO₃ (already balanced)
- BaCl₂ + H₂SO₄ → BaSO₄ + HCl Ans: BaCl₂ + H₂SO₄ → BaSO₄ + 2HCl
Q3. Write balanced chemical equations with state symbols for the following:
- Barium chloride and sodium sulphate solutions react to give insoluble barium sulphate and sodium chloride solution. Ans: BaCl₂(aq) + Na₂SO₄(aq) → BaSO₄(s) + 2NaCl(aq)
- Sodium hydroxide solution reacts with hydrochloric acid solution to produce sodium chloride solution and water. Ans: NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l)
Q4. Translate the following into balanced chemical equations:
- Hydrogen gas combines with nitrogen to form ammonia. Ans: 3H₂(g) + N₂(g) → 2NH₃(g)
- Hydrogen sulphide gas burns in air to give water and sulphur dioxide. Ans: 2H₂S(g) + 3O₂(g) → 2H₂O(l) + 2SO₂(g)
- Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate. Ans: 3BaCl₂(aq) + Al₂(SO₄)₃(aq) → 2AlCl₃(aq) + 3BaSO₄(s)
- Potassium metal reacts with water to give potassium hydroxide and hydrogen gas. Ans: 2K(s) + 2H₂O(l) → 2KOH(aq) + H₂(g)
Combination Reaction Important Questions
A combination reaction produces a single product from two or more reactants. Many combination reactions are also exothermic.
Q1. Why should a magnesium ribbon be cleaned before burning in air? Ans: Magnesium ribbon should be cleaned with sandpaper before burning because it has a protective layer of basic magnesium carbonate on its surface. This layer prevents the ribbon from burning properly. Removing it ensures the magnesium burns in air with a dazzling white flame.
Q2. The reaction of calcium oxide with water is a combination reaction. Write the chemical equation and name the type of energy change involved. Ans: CaO(s) + H₂O(l) → Ca(OH)₂(aq) + Heat. This is an exothermic combination reaction. The beaker becomes warm because heat is released during the formation of calcium hydroxide (slaked lime).
Q3. Identify the type of reaction: 2H₂(g) + O₂(g) → 2H₂O(l) Ans: This is a combination reaction. Two reactants, hydrogen and oxygen, combine to form a single product, water. It is also an exothermic reaction.
Q4. Give one example each of a combination reaction that is also: i. Exothermic: CaO + H₂O → Ca(OH)₂ + Heat ii. Endothermic: N₂ + O₂ → 2NO (requires very high temperature)
Decomposition Reaction Important Questions
Decomposition is the opposite of combination. One substance breaks into two or more simpler substances. Energy is always required, as heat, light, or electricity.
Q1. Write one equation each for decomposition reactions where energy is supplied in the form of:
- Heat (thermal decomposition): Ans: CaCO₃(s) → CaO(s) + CO₂(g) or MgCO₃(s) → MgO(s) + CO₂(g)
- Light (photodecomposition): Ans: 2AgCl(s) → 2Ag(s) + Cl₂(g) [in sunlight]
- Electricity (electrolytic decomposition): Ans: 2H₂O(l) → 2H₂(g) + O₂(g) [electric current]
Q2. Why are decomposition reactions called the opposite of combination reactions? Ans: In a combination reaction, two or more substances react to form one product. In a decomposition reaction, one substance breaks down into two or more simpler products. The direction of change is opposite. For example, CaO + H₂O → Ca(OH)₂ is combination, while CaCO₃ → CaO + CO₂ is decomposition.
Q3. Ferrous sulphate crystals are green. What happens when they are heated? Ans: Ferrous sulphate crystals lose water first and change colour. On further heating, they decompose: 2FeSO₄(s) → Fe₂O₃(s) + SO₂(g) + SO₃(g). The green crystals turn reddish-brown (ferric oxide). A characteristic odour of burning sulphur is noticed.
Q4. What happens when lead nitrate is heated? Ans: 2Pb(NO₃)₂(s) → 2PbO(s) + 4NO₂(g) + O₂(g). Brown fumes of nitrogen dioxide are emitted. This is a thermal decomposition reaction.
Q5. A compound X with pH = 7 is used for drinking and its acidified solution decomposes on passing electricity to produce gases Y and Z. Volume of Y is double that of Z. Y is highly combustible and Z supports combustion. Identify X, Y, and Z. Ans: X = H₂O (water), Y = H₂ (hydrogen), Z = O₂ (oxygen). The reaction: 2H₂O(l) → 2H₂(g) + O₂(g) using electric current.
Displacement Reaction Important Questions
In a displacement reaction, a more reactive element displaces a less reactive element from its compound.
Q1. Why does the colour of copper sulphate solution change when an iron nail is dipped in it? Ans: Iron is more reactive than copper. When an iron nail is placed in copper sulphate solution, iron displaces copper: Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s). The blue colour of copper sulphate fades as copper is deposited on the iron nail and iron sulphate (green) forms in solution.
Q2. With the help of an activity, show that iron is more reactive than copper. Ans: Take copper sulphate solution in a test tube. Drop iron nails into it. After 20 minutes, the blue colour fades and the nails become reddish-brown. This confirms iron displaces copper: Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s). Iron is more reactive than copper.
Q3. Identify whether the following is a displacement reaction. Fe₂O₃ + 2Al → Al₂O₃ + 2Fe Ans: Yes, this is a displacement reaction. Aluminium is more reactive than iron and displaces iron from iron oxide. It is also called the thermite reaction and is an exothermic reaction.
Q4. In the refining of silver, recovery of silver from silver nitrate solution involves displacement by copper. Write the reaction. Ans: Cu(s) + 2AgNO₃(aq) → Cu(NO₃)₂(aq) + 2Ag(s)
Double Displacement Reaction Important Questions
Double displacement reactions involve exchange of ions between two compounds. They often produce a precipitate, water, or a gas.
Q1. What is a precipitation reaction? Explain with an example. Ans: A precipitation reaction produces an insoluble solid (precipitate) when two solutions are mixed. For example: Na₂SO₄(aq) + BaCl₂(aq) → BaSO₄(s) + 2NaCl(aq). The white precipitate of barium sulphate forms because SO₄²⁻ and Ba²⁺ ions combine to form an insoluble compound.
Q2. When solutions of lead(II) nitrate and potassium iodide are mixed:
- What is the colour of the precipitate? Ans: The precipitate is yellow. It is lead(II) iodide (PbI₂).
- Write the balanced chemical equation. Ans: Pb(NO₃)₂(aq) + 2KI(aq) → PbI₂(s) + 2KNO₃(aq)
- Is this a double displacement reaction? Ans: Yes. Both compounds exchange their ions. Pb²⁺ combines with I⁻ and K⁺ combines with NO₃⁻.
Q3. Give an example of a double displacement reaction other than precipitation. Ans: NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l). This is a neutralisation reaction and also a double displacement reaction where H⁺ and OH⁻ ions combine to form water.
Oxidation and Reduction Important Questions
Oxidation is the gain of oxygen or loss of hydrogen. Reduction is the loss of oxygen or gain of hydrogen. These always occur together in redox reactions.
The chemical reaction and equation class 10 questions and answers on redox are among the most common 3-mark board questions. Practise identifying both the oxidised and reduced substance in every equation.
Q1. Identify the substances oxidised and reduced in the following:
- 4Na(s) + O₂(g) → 2Na₂O(s) Ans: Sodium is oxidised (gains oxygen). Oxygen is reduced (gains electrons/combines with metal to form oxide).
- CuO(s) + H₂(g) → Cu(s) + H₂O(l) Ans: Hydrogen is oxidised (gains oxygen). Copper oxide is reduced (loses oxygen). This is a redox reaction.
Q2. A reddish-brown metal X when heated in oxygen forms a black compound Y. Passing hydrogen gas over heated Y gives back X. Identify X and Y. Write chemical reactions. Ans: X = Cu (copper), Y = CuO (copper oxide). Reactions: 2Cu(s) + O₂(g) → 2CuO(s) (oxidation) CuO(s) + H₂(g) → Cu(s) + H₂O(l) (reduction)
Q3. Can a reaction be classified as both a decomposition and a redox reaction? Ans: Yes. For example: 2H₂O(l) → 2H₂(g) + O₂(g). Here water decomposes (decomposition reaction) and hydrogen loses oxygen (reduction) while oxygen is released (oxidation). This is both decomposition and a redox reaction.
Q4. Why is respiration considered an exothermic reaction? Ans: Respiration releases energy in the form of heat. Glucose reacts with oxygen in body cells: C₆H₁₂O₆(aq) + 6O₂(aq) → 6CO₂(aq) + 6H₂O(l) + energy. Since heat is released during the reaction, it is exothermic.
Corrosion and Rancidity Important Questions
These are real-life applications of oxidation. Corrosion affects metals and rancidity affects fats and oils. Both appear regularly in 2-mark and 3-mark board questions.
Q1. Define rusting. Why do we apply paint on iron articles? Ans: Rusting is the formation of reddish-brown ferric oxide on the surface of iron when exposed to moisture and air for a long time. Paint is applied to iron articles to prevent contact between iron, oxygen, and water, which stops the rusting process.
Q2. Astha collected silver coins and copper coins. She observed a black coating on silver and a green coating on copper. What chemical phenomenon is responsible? Name the chemical compounds formed. Ans: Corrosion is responsible. The black coating on silver is silver sulphide (Ag₂S), formed by reaction with sulphur compounds in air. The green coating on copper is a mixture of copper carbonate and copper hydroxide (CuCO₃.Cu(OH)₂), formed by reaction with CO₂ and moisture.
Q3. Why are food particles preferably packed in aluminium foil? Ans: Aluminium does not corrode in the atmosphere. A protective layer of aluminium oxide (Al₂O₃) forms on its surface, preventing further reaction with air and water. This keeps food particles from spoiling even if stored for a long time.
Q4. Oil and fat-containing food items are flushed with nitrogen. Why? Ans: Fats and oils oxidise when exposed to air, making food rancid. The smell and taste change. Nitrogen is an inert gas and does not react with oil or fat. Flushing bags with nitrogen removes oxygen and prevents oxidation, keeping food fresh longer.
Q5. What is rancidity? Give two methods to prevent it. Ans: Rancidity is the oxidation of fats and oils in food over time, causing a change in smell and taste. Two prevention methods: (1) store food in airtight containers to limit oxygen exposure, and (2) add antioxidants to food items containing fats and oils.
Class 10 Science Chapter 1 MCQs with Answers
Students looking for science class 10 chapter 1 question answer often start with MCQs. These help with quick recall and reaction-type identification.
Q1. Some crystals of copper sulphate were dissolved in water. The colour of the solution obtained would be: A. Green B. Red C. Blue D. Brown Ans: (c) Blue
Q2. The reaction H₂ + Cl₂ → 2HCl represents: A. Oxidation B. Reduction C. Decomposition D. Combination Ans: (d) Combination
Q3. In the reaction PbO + C → Pb + CO, C acts as: A. An oxidising agent B. An oxidising agent C. A reduction agent D. None Ans: (c) C acts as a reducing agent. It removes oxygen from PbO.
Q4. Chemically rust is: A. Hydrated ferrous oxide B. Hydrated ferric oxide C. Only ferric oxide D. None Ans: (b) Hydrated ferric oxide
Q5. The reaction between lead nitrate and potassium iodide in aqueous solution is an example of: A. Decomposition B. Displacement C. Double displacement D. Neutralisation Ans: (c) Double displacement reaction
Q6. Which of the following reactions is NOT correct? A. Zn + CuSO₄ → ZnSO₄ + Cu B. 2Ag + Cu(NO₃)₂ → 2AgNO₃ + Cu C. Fe + CuSO₄ → FeSO₄ + Cu D. Mg + 2HCl → MgCl₂ + H₂ Ans: (b) Silver is less reactive than copper and cannot displace copper from its salt solution.
Q7. What happens when dilute hydrochloric acid is added to iron filings? A. Hydrogen gas and iron chloride are produced B. Chlorine gas and iron hydroxide are produced C. No reaction takes place D. Iron salt and water are produced Ans: (a) Hydrogen gas and iron chloride (FeCl₂) are produced.
Q8. Which of the statements about 2PbO(s) + C(s) → 2Pb(s) + CO₂(g) are incorrect? A. Lead is getting reduced B. Carbon dioxide is getting oxidised C. Carbon is getting oxidised D. Lead oxide is getting reduced Ans: (i) (a) and (b). Lead is being reduced (loses oxygen) and carbon is being oxidised (gains oxygen). Carbon dioxide is the product and is not getting oxidised.
Q9. Fe₂O₃ + 2Al → Al₂O₃ + 2Fe. This reaction is an example of: A. Combination B. Double displacement C. Decomposition D. Displacement Ans: (d) Displacement reaction
Q10. Dissolving sugar is an example of: A. Physical change B. Chemical change C. Redox reaction D. None Ans: (a) Physical change. No new substance is formed. The sugar dissolves but can be recovered.
Class 10 Science Chapter 1 Very Short Answer Questions (1 Mark)
Q1. Name the type of reaction: A → B + C Ans: Decomposition reaction.
Q2. Name the type of reaction: A + B → AB Ans: Combination reaction.
Q3. What is the chemical name of rust? Ans: Hydrated ferric oxide (Fe₂O₃.xH₂O).
Q4. What does the symbol (aq) represent in a chemical equation? Ans: It means the substance is dissolved in water (aqueous solution).
Q5. Name the gas evolved when dilute HCl is added to zinc granules. Ans: Hydrogen gas (H₂).
Q6. What is an endothermic reaction? Ans: A reaction that absorbs energy from the surroundings is called an endothermic reaction.
Class 10 Science Chapter 1 Short Answer Questions (2 Marks)
Q1. Identify the type of chemical reaction:
i. A → B + C Ans: Decomposition reaction — one reactant breaks into two products.
ii. AD + CB → AC + DB Ans: Double displacement reaction — ions are exchanged between the two compounds.
Q2. Why does silver not evolve hydrogen gas when reacted with dilute H₂SO₄? Ans: Silver is less reactive than hydrogen in the reactivity series. It cannot displace hydrogen from dilute sulphuric acid, so no hydrogen gas is evolved.
Q3. Why is combustion reaction considered an oxidation reaction? Ans: In combustion, a substance reacts with oxygen to produce heat and light: CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g). Since oxygen is added to the substance, it is an oxidation reaction.
Q4. What happens when CO₂ gas is bubbled through lime water in excess? Ans: Initially lime water turns milky due to formation of calcium carbonate (CaCO₃). On passing excess CO₂, calcium bicarbonate forms and the solution turns colourless: CaCO₃(s) + CO₂(g) + H₂O(l) → Ca(HCO₃)₂(aq).
Q5. Write the balanced reaction for slaked lime formation and name the type of reaction. Ans: CaO(s) + H₂O(l) → Ca(OH)₂(aq) + Heat. This is a combination reaction and also an exothermic reaction.
Class 10 Science Chapter 1 Long Answer Questions (3 and 5 Marks)
Q1 (3 Marks). What is the difference between displacement and double displacement reactions? Write one equation for each. Ans: In displacement reaction, a more reactive element displaces a less reactive element from its compound. Only one element changes position. Example: Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s)
In double displacement reaction, two compounds exchange their ions to form two new compounds. Both reactants change. Example: Na₂SO₄(aq) + BaCl₂(aq) → BaSO₄(s) + 2NaCl(aq)
Q2 (3 Marks). Explain exothermic and endothermic reactions with two examples each. Ans: Exothermic reactions release heat during the reaction. Examples: (i) CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g) + heat (ii) CaO(s) + H₂O(l) → Ca(OH)₂(aq) + heat
Endothermic reactions absorb heat from the surroundings. Examples: (i) CaCO₃(s) → CaO(s) + CO₂(g) (requires heat) (ii) N₂(g) + O₂(g) → 2NO(g) (requires very high temperature)
Q3 (5 Marks). You are given iron nails, copper sulphate solution, BaCl₂, ferrous sulphate crystals, and quick lime. Make five reactions possible from these materials. Ans: i. BaCl₂(aq) + CuSO₄(aq) → BaSO₄(s) + CuCl₂(aq) — double displacement ii. 2Cu(s) + O₂(g) → 2CuO(s) — combination iii. 2FeSO₄(s) → Fe₂O₃(s) + SO₂(g) + SO₃(g) — decomposition iv. 2FeSO₄.7H₂O(s) → 2FeSO₄(s) + 14H₂O — dehydration v. CaO(s) + H₂O(l) → Ca(OH)₂(aq) + Heat — combination and exothermic
Q4 (5 Marks). A student dropped marble pieces into dilute HCl in a test tube. The evolved gas was passed through lime water. Describe observations and write balanced equations for both changes observed. Ans: Marble reacts with dilute HCl to produce CO₂ gas: CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l) + CO₂(g)
When CO₂ is passed through lime water, it turns milky: Ca(OH)₂(aq) + CO₂(g) → CaCO₃(s) + H₂O(l)
On passing excess CO₂, the milky solution turns colourless as calcium bicarbonate forms: CaCO₃(s) + CO₂(g) + H₂O(l) → Ca(HCO₃)₂(aq)
Important Chemical Equations for Class 10 Science Chapter 1
These are the equations to memorise for board exams in 2026. Every one of these has appeared in school tests or board papers.
- Magnesium burning in air: 2Mg(s) + O₂(g) → 2MgO(s)
- Zinc with sulphuric acid: Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g)
- Slaked lime formation: CaO(s) + H₂O(l) → Ca(OH)₂(aq) + Heat
- Whitewashing reaction: Ca(OH)₂(aq) + CO₂(g) → CaCO₃(s) + H₂O(l)
- Thermal decomposition of calcium carbonate: CaCO₃(s) → CaO(s) + CO₂(g)
- Decomposition of ferrous sulphate: 2FeSO₄(s) → Fe₂O₃(s) + SO₂(g) + SO₃(g)
- Electrolysis of water: 2H₂O(l) → 2H₂(g) + O₂(g)
- Silver chloride in sunlight: 2AgCl(s) → 2Ag(s) + Cl₂(g)
- Iron displacing copper: Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s)
- Precipitation of barium sulphate: Na₂SO₄(aq) + BaCl₂(aq) → BaSO₄(s) + 2NaCl(aq)
- Copper oxidation: 2Cu(s) + O₂(g) → 2CuO(s)
- Reduction of copper oxide: CuO(s) + H₂(g) → Cu(s) + H₂O(l)
- Respiration: C₆H₁₂O₆(aq) + 6O₂(aq) → 6CO₂(aq) + 6H₂O(l) + energy
- Refining of silver: Cu(s) + 2AgNO₃(aq) → Cu(NO₃)₂(aq) + 2Ag(s)
- Lead nitrate thermal decomposition: 2Pb(NO₃)₂(s) → 2PbO(s) + 4NO₂(g) + O₂(g)
Chemical Reaction and Equation Class 10 PYQ Questions
Students searching for chemical reaction and equation class 10 pyq should practise repeated board patterns first. PYQs show how balancing and reaction-type questions are framed.
PYQ 1. Write the balanced equation and identify the type of reaction:
- Potassium bromide (aq) + Barium iodide (aq) → Potassium iodide (aq) + Barium bromide (s) Ans: 2KBr(aq) + BaI₂(aq) → 2KI(aq) + BaBr₂(s). Double displacement reaction.
- Zinc carbonate (s) → Zinc oxide (s) + Carbon dioxide (g) Ans: ZnCO₃(s) → ZnO(s) + CO₂(g). Decomposition reaction.
- Hydrogen (g) + Chlorine (g) → Hydrogen chloride (g) Ans: H₂(g) + Cl₂(g) → 2HCl(g). Combination reaction.
- Magnesium (s) + Hydrochloric acid (aq) → Magnesium chloride (aq) + Hydrogen (g) Ans: Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g). Displacement reaction.
PYQ 2. Write the balanced equation and identify oxidised and reduced substances:
- 4Na(s) + O₂(g) → 2Na₂O(s) Ans: Sodium is oxidised (gains oxygen). Oxygen molecule is the oxidising agent.
- CuO(s) + H₂(g) → Cu(s) + H₂O(l) Ans: Hydrogen is oxidised (gains oxygen). Copper oxide is reduced (loses oxygen).
PYQ 3. A pale green substance A in a test tube is heated over a burner. A brown residue B forms along with two gases with burning sulphur smell. Identify A and B. Write the equation. Ans: A = FeSO₄ (ferrous sulphate, pale green crystals). B = Fe₂O₃ (ferric oxide, reddish-brown). Equation: 2FeSO₄(s) → Fe₂O₃(s) + SO₂(g) + SO₃(g)
Chemical Reaction and Equation Class 10 Extra Questions
Students also search for chemical reaction and equation class 10 extra questions before tests and pre-boards. These questions give extra concept practice beyond direct NCERT examples.
Q1. Why is breathing called an exothermic process? Breathing releases energy from glucose. That energy supports body functions.
Q2. Why is a reaction with one product not always a combination reaction? You must check the reactants too. Two or more reactants should combine into one product.
Q3. Why are state symbols important in equations? State symbols show physical state. They help identify gas evolution, precipitates, and solution reactions.
Most Important Questions of Chemistry Class 10 Chapter 1
These are the most important questions of chemistry class 10 chapter 1 for final revision. Practise them before school tests, pre-boards, and board exams in 2026.
- Why should equations be balanced?
- How do you identify a decomposition reaction?
- What is the difference between displacement and double displacement?
- Why is CuO + H₂ a redox reaction?
- How do you prevent rusting and rancidity?
Class 10 Science Chapter 1 Test Paper with Solution
Students searching for class 10 science chapter 1 test paper with solution usually want quick self-check practice. Use this mini test before moving to full sample papers.
Q1. Balance: Fe + H₂O → Fe₃O₄ + H₂ Ans: 3Fe + 4H₂O → Fe₃O₄ + 4H₂
Q2. Identify the reaction: AgCl → Ag + Cl₂ Ans: Decomposition reaction.
Q3. Why is rusting a chemical change? Ans: A new substance forms on iron. That makes it a chemical change.
Q4. What is formed when CO₂ reacts with lime water? Ans: Calcium carbonate.
Q5. Name one method to prevent rancidity. Ans: Store food in airtight containers.
Common Mistakes in Chapter 1
Many students lose marks in easy questions because of avoidable errors. Fix these before your 2026 board exams.
- Writing skeletal equations without balancing them
- Missing state symbols in board-style answers
- Confusing oxidation with reduction
- Mixing displacement and double displacement
- Forgetting the reason behind corrosion and rancidity
How to Prepare Class 10 Science Chapter 1 for Board Exams
Chapter 1 is scoring because the question patterns repeat. Use this order while revising.
Step 1: Memorise the important equations. Step 2: Practise balancing three equations daily. Step 3: Learn reaction-type clues. Step 4: Write 3-mark answers in structure. Step 5: Practise PYQs under time limits.
