Assertion and Reason Questions Class 10 Science – Practice with Answers
Assertion and Reason type questions are an important part of the CBSE Class 10 Science exams, testing both concept clarity and logical reasoning. These questions present two statements — an Assertion (A) and a Reason (R) — and require students to evaluate the truth of each and the relationship between them.
This format helps students:
- Deepen their understanding of scientific concepts
- Apply knowledge logically
- Prepare effectively for competency-based questions in exams
In this section, you will find well-curated Assertion and Reason questions from various chapters of Class 10 Science. Each question includes the correct answer and explanation, making it ideal for self-assessment and revision.
Chemical reaction and equations Assertion and Reason
Choose the correct option:
- (A) Both Assertion and Reason are true, and Reason is the correct explanation of the Assertion.
- (B) Both Assertion and Reason are true, but Reason is not the correct explanation of the Assertion.
- (C) Assertion is true but Reason is false.
- (D) Assertion is false but Reason is true.
Q1. Assertion (A): Magnesium ribbon burns with a dazzling white flame in air.
Reason (R): Magnesium reacts with oxygen to form magnesium oxide.
Answer: (A)
Q2. Assertion (A): Rusting of iron is a physical change.
Reason (R): A new substance is formed when iron rusts.
Answer: (D)
Q3. Assertion (A): Respiration is considered an exothermic reaction.
Reason (R): Energy is released during the breakdown of glucose.
Answer: (A)
Q4.Assertion (A): Copper does not react with dilute hydrochloric acid.
Reason (R): Copper is less reactive than hydrogen.
Answer: (A)
Q5.Assertion (A): A chemical equation must be balanced.
Reason (R): To obey the Law of Conservation of Mass.
Answer: (A)
Q6. Assertion (A): Photosynthesis is an endothermic reaction.
Reason (R): It releases energy in the form of sunlight.
Answer: (C)
Q7.Assertion (A): Ferrous sulphate crystals are green in color.
Reason (R): They contain water of crystallization.
Answer: (A)
Q8.Assertion (A): Precipitation reaction is a type of double displacement reaction.
Reason (R): Two compounds exchange ions to form new compounds, one of which is insoluble.
Answer: (A)
Q9.Assertion (A): Burning of coal is a chemical change.
Reason (R): Carbon dioxide is formed and heat is released.
Answer: (A)
Q10 Assertion (A): In a displacement reaction, a less reactive metal displaces a more reactive metal.
Reason (R): Reactivity series is used to predict displacement reactions.
Answer: (D)
Q11. Assertion (A): Silver chloride turns grey in sunlight.
Reason (R): It decomposes to silver and chlorine gas.
Answer: (A)
Q12. Assertion (A): Heat is absorbed during decomposition of calcium carbonate.
Reason (R): It is an endothermic reaction.
Answer: (A)
Q13. Assertion (A): In chemical reactions, only the physical appearance of the substance changes.
Reason (R): No new substance is formed.
Answer: (D)
Q14. Assertion (A): Reaction of zinc with dilute sulphuric acid is a redox reaction.
Reason (R): Zinc is oxidized and hydrogen ions are reduced.
Answer: (A)
Q15. Assertion (A): Iron nails become brownish when dipped in copper sulphate solution.
Reason (R): Iron is more reactive than copper and displaces it.
Answer: (A)
Q16. Assertion (A): Combination reactions always release heat.
Reason (R): They are always exothermic.
Answer: (C)
Q17. Assertion (A): The reaction between barium chloride and sodium sulphate forms a white precipitate.
Reason (R): Barium sulphate is insoluble in water.
Answer: (A)
Q18.Assertion (A): The formation of water from hydrogen and oxygen is a displacement reaction.
Reason (R): It involves combination of two elements.
Answer: (D)
Q19.Assertion (A): Decomposition of lead nitrate produces a brown gas.
Reason (R): Nitrogen dioxide is evolved during thermal decomposition.
Answer: (A)
Q20. Assertion (A): Chemical reactions involve breaking and making of bonds.
Reason (R): Bond energy is absorbed to break bonds and released when bonds are formed.
Answer: (A)
Assertion and Reason Questions Class 10 Science – Practice with Answers
Read Also : Activity 1.1 ( burning of magnesium ribbon )
Acid , Base and Salt Assertion and Reason
Assertion (A): Metals are malleable and ductile.
Reason (R): Metals have strong metallic bonds.
Answer: (A)
Assertion (A): Sodium reacts explosively with cold water.
Reason (R): It forms sodium hydroxide and hydrogen gas.
Answer: (A)
Assertion (A): Silver is more reactive than copper.
Reason (R): Silver can displace copper from copper salt solution.
Answer: (D)
Assertion (A): Oxygen is a non-metal.
Reason (R): It gains electrons to form oxide ions.
Answer: (A)
Assertion (A): All metals are hard.
Reason (R): Metal atoms are closely packed.
Answer: (C)
Assertion (A): Non-metals are used in fertilizers.
Reason (R): Non-metals like nitrogen and phosphorus are essential for plant growth.
Answer: (A)
Assertion (A): Metals above hydrogen in the reactivity series can displace hydrogen from acids.
Reason (R): These metals are more reactive than hydrogen.
Answer: (A)
Assertion (A): Sulphur is a non-metal and is brittle.
Reason (R): Non-metals are brittle in solid state.
Answer: (A)
Assertion (A): Mercury is the only liquid metal at room temperature.
Reason (R): It has very low melting point.
Answer: (A)
Assertion (A): Acids turn blue litmus red.
Reason (R): Acids contain hydroxide ions.
Answer: (C)
Assertion (A): A solution of baking soda in water is basic in nature.
Reason (R): It releases hydroxide ions in water.
Answer: (A)
Assertion (A): HCl gas does not show acidic behavior in the absence of water.
Reason (R): Acids release H⁺ ions only in aqueous solution.
Answer: (A)
Assertion (A): Tooth enamel is corroded by acids formed in the mouth.
Reason (R): Acids react with calcium phosphate in enamel.
Answer: (A)
Assertion (A): Dry HCl gas turns blue litmus red.
Reason (R): Acids turn blue litmus red only in aqueous solution.
Answer: (D)
Assertion (A): Sodium hydroxide reacts with zinc to produce hydrogen gas.
Reason (R): Zinc is an amphoteric metal.
Answer: (A)
Assertion (A): pH of pure water is 7 at 25°C.
Reason (R): Pure water is neutral in nature.
Answer: (A)
Assertion (A): Phenolphthalein remains colorless in acidic solutions.
Reason (R): Phenolphthalein is a pH indicator that turns pink in basic solutions.
Answer: (A)
Assertion (A): Acids react with metal carbonates to liberate carbon dioxide.
Reason (R): Metal carbonates are basic in nature.
Answer: (B)
Assertion (A): Neutralization reaction is always exothermic.
Reason (R): Heat is released during the combination of H⁺ and OH⁻ ions.
Answer: (A)
Assertion (A): Common salt is neutral in nature.
Reason (R): It is formed from the reaction of a strong acid and a strong base.
Answer: (A)
Assertion (A): Sodium chloride is used in the preparation of many important industrial chemicals.
Reason (R): It undergoes electrolysis to give chlorine and sodium hydroxide.
Answer: (A)
Assertion (A): Acetic acid is a strong acid.
Reason (R): It dissociates completely in water.
Answer: (D)
Assertion (A): Strong acids have higher pH than weak acids.
Reason (R): pH increases with acidity.
Answer: (D)
Assertion (A): Lemon juice is a natural acid.
Reason (R): It contains citric acid.
Answer: (A)
Assertion (A): Bleaching powder is used as a disinfectant.
Reason (R): It releases chlorine gas on exposure to air.
Answer: (A)
Assertion (A): Crystals of washing soda lose water of crystallization on heating.
Reason (R): It is a hydrated salt.
Answer: (A)
Assertion (A): Ammonia solution turns red litmus blue.
Reason (R): Ammonia is a base.
Answer: (A)
Assertion (A): Salts formed from weak acids and strong bases are basic in nature.
Reason (R): Weak acids do not dissociate completely.
Answer: (A)
Assertion (A): Acids generate hydrogen gas when they react with metals.
Reason (R): Hydrogen gas is released when metals replace hydroxide ions.
Answer: (C)
Assertion (A): HCl shows acidic behavior only in the presence of water.
Reason (R): HCl produces hydrogen ions in aqueous solution.
Answer: (A)
Assertion (A): Tooth decay starts when the pH of mouth falls below 5.5.
Reason (R): Acidic medium in mouth promotes bacterial activity.
Answer: (A
Assertion (A): Sodium hydroxide reacts with zinc to form sodium zincate.
Reason (R): Zinc is an amphoteric metal.
Answer: (A)
Assertion (A): Acids conduct electricity in aqueous solution.
Reason (R): They produce hydrogen ions which are responsible for conduction.
Answer: (A)
Assertion (A): Phenolphthalein turns pink in basic solution.
Reason (R): It is a natural indicator.
Answer: (C)
Assertion (A): The pH of lemon juice is less than 7.
Reason (R): Lemon juice contains citric acid.
Answer: (A)
Assertion (A): Baking soda is used in antacids.
Reason (R): It neutralizes excess acid in the stomach.
Answer: (A)
Assertion (A): Weak acids have higher pH than strong acids.
Reason (R): Weak acids ionize partially in water.
Answer: (A)
Assertion (A): Blue litmus turns red in the solution of vinegar.
Reason (R): Vinegar is a weak base.
Answer: (C)
Assertion (A): pH scale measures the concentration of OH⁻ ions.
Reason (R): Acids have more OH⁻ ions than bases.
Answer: (D)
Assertion (A): Acidic and basic solutions conduct electricity.
Reason (R): They produce ions in water.
Answer: (A)
Assertion (A): Bleaching powder is used in water treatment plants.
Reason (R): It releases chlorine which helps in disinfecting water.
Answer: (A)
Assertion (A): Common salt is formed by neutralization.
Reason (R): It is formed by the reaction of hydrochloric acid and sodium hydroxide.
Answer: (A)
Assertion (A): Strong bases have pH closer to 14.
Reason (R): They completely dissociate in water.
Answer: (A)
Assertion (A): Washing soda is used to remove hardness of water.
Reason (R): It reacts with magnesium and calcium salts.
Answer: (A)
Assertion (A): Dry hydrogen chloride gas does not turn blue litmus red.
Reason (R): It does not ionize in the absence of water.
Answer: (A)
Assertion (A): Crystals of copper sulphate turn white on heating.
Reason (R): Water of crystallization is removed.
Answer: (A)
Assertion (A): Milk of magnesia is used for acidity relief.
Reason (R): It is alkaline and neutralizes stomach acid.
Answer: (A)
Assertion (A): Ammonium chloride solution has a pH less than 7.
Reason (R): It is a salt of a strong acid and weak base.
Answer: (A)
Assertion and Reason Questions Class 10 Science – Practice with Answers
Metal and non-metal Assertion and Reason
Choose the correct option:
- (A) Both Assertion and Reason are true, and Reason is the correct explanation of the Assertion.
- (B) Both Assertion and Reason are true, but Reason is not the correct explanation of the Assertion.
- (C) Assertion is true but Reason is false.
- (D) Assertion is false but Reason is true.
Assertion (A): Sodium and potassium are stored in kerosene.
Reason (R): They react vigorously with water and air.
Answer: (A)
Assertion (A): Zinc can displace copper from copper sulphate solution.
Reason (R): Zinc is less reactive than copper.
Answer: (C)
Assertion (A): Zinc can displace copper from copper sulphate solution.
Reason (R): Zinc is less reactive than copper.
Answer: (C)
Assertion (A): Non-metals do not conduct electricity.
Reason (R): They do not have free electrons.
Answer: (A)
Assertion (A): Copper cannot displace zinc from zinc sulphate solution.
Reason (R): Zinc is more reactive than copper.
Answer: (A)
Assertion (A): Carbon is used to reduce metal oxides to metal.
Reason (R): Carbon is a good reducing agent.
Answer: (A
Assertion (A): Iron reacts with steam to form iron oxide and hydrogen gas.
Reason (R): Iron is more reactive than hydrogen.
Answer: (A)
Assertion (A): Gold and silver are found in free state in nature.
Reason (R): They are very reactive metals.
Answer: (C)
Assertion (A): Metals are sonorous.
Reason (R): They produce sound when struck.
Answer: (A)
Assertion (A): Aluminium forms a protective oxide layer on its surface.
Reason (R): This oxide layer prevents further oxidation.
Answer: (A)
Assertion (A): Non-metals form acidic oxides.
Reason (R): Non-metals react with oxygen to form acidic oxides.
Answer: (A)
Assertion (A): Iron is extracted from its ore by reduction.
Reason (R): Iron ore is highly reactive.
Answer: (C)
Assertion (A): Metals are malleable and ductile.
Reason (R): Metals have strong metallic bonds.
Answer: (A)
Assertion (A): Sodium reacts explosively with cold water.
Reason (R): It forms sodium hydroxide and hydrogen gas.
Answer: (A)
Assertion (A): Silver is more reactive than copper.
Reason (R): Silver can displace copper from copper salt solution.
Answer: (D)
Assertion (A): Oxygen is a non-metal.
Reason (R): It gains electrons to form oxide ions.
Answer: (A)
Assertion (A): All metals are hard.
Reason (R): Metal atoms are closely packed.
Answer: (C)
Assertion (A): Non-metals are used in fertilizers.
Reason (R): Non-metals like nitrogen and phosphorus are essential for plant growth.
Answer: (A)
Assertion (A): Metals above hydrogen in the reactivity series can displace hydrogen from acids.
Reason (R): These metals are more reactive than hydrogen.
Answer: (A)
Assertion (A): Sulphur is a non-metal and is brittle.
Reason (R): Non-metals are brittle in solid state.
Answer: (A)
Assertion (A): Mercury is the only liquid metal at room temperature.
Reason (R): It has very low melting point.
Answer: (A)
Assertion (A): Metals are good conductors of electricity.
Reason (R): Metals have free-moving electrons that carry electric current.
Answer: (A)
Assertion (A): Copper cannot displace iron from iron sulphate solution.
Reason (R): Copper is more reactive than iron.
Answer: (D)
Assertion (A): Non-metals are generally poor conductors of heat.
Reason (R): Non-metals lack free electrons needed to transfer energy.
Answer: (A)
Assertion (A): Sodium reacts vigorously with water.
Reason (R): Sodium has high reactivity due to its large atomic size and tendency to lose electrons easily.
Answer: (A)
Assertion (A): Gold and platinum are used in making jewellery.
Reason (R): They are highly reactive and easily form compounds.
Answer: (C)
Assertion (A): Non-metals like chlorine are used in water purification.
Reason (R): Non-metals can have oxidizing properties.
Answer: (A)
Assertion (A): Zinc can reduce copper oxide to copper.
Reason (R): Zinc is more reactive than copper.
Answer: (A)
Assertion (A): Metals can form both acidic and basic oxides.
Reason (R): All metals are amphoteric in nature.
Answer: (C)
Assertion (A): Non-metals gain electrons to form negative ions.
Reason (R): Non-metals have high electronegativity.
Answer: (A)
Assertion (A): Iron corrodes when exposed to air and moisture.
Reason (R): Iron reacts with water and oxygen to form rust (hydrated iron oxide).
Answer: (A)
Assertion (A): Sodium and potassium are kept under kerosene.
Reason (R): They react with oxygen and water in air rapidly.
Answer: (A)
Assertion (A): Aluminium is used to extract chromium from its oxide.
Reason (R): Aluminium is more reactive and can reduce less reactive metal oxides.
Answer: (A)
Assertion (A): Sulphur dioxide is acidic in nature.
Reason (R): It dissolves in water to form sulphuric acid.
Answer: (C)
Assertion (A): Iodine is a lustrous non-metal.
Reason (R): Some non-metals show metallic properties.
Answer: (A)
Assertion (A): Magnesium reacts faster with steam than with cold water.
Reason (R): Steam provides more energy to start the reaction.
Answer: (A)
Assertion (A): Carbon cannot reduce aluminium oxide to aluminium.
Reason (R): Aluminium is more reactive than carbon.
Answer: (A)
Assertion (A): Iron is used to construct bridges and buildings.
Reason (R): Iron has good tensile strength and hardness.
Answer: (A)
Assertion (A): Mercury is a poor conductor of heat compared to other metals.
Reason (R): It is a liquid and has loosely packed atoms.
Answer: (A)
Assertion (A): Phosphorus is stored under water.
Reason (R): It reacts spontaneously with oxygen in air.
Answer: (A)
Assertion (A): Hydrogen gas is released when metals react with acids.
Reason (R): Metals displace hydrogen ions from acids to form salts.
Answer: (A)
Assertion and Reason Questions Class 10 Science – Practice with Best Answers
Carbon and its compound Assertion and Reason
Choose the correct option:
- (A) Both Assertion and Reason are true, and Reason is the correct explanation of the Assertion.
- (B) Both Assertion and Reason are true, but Reason is not the correct explanation of the Assertion.
- (C) Assertion is true but Reason is false.
- (D) Assertion is false but Reason is true.
Assertion (A): Carbon forms a large number of compounds.
Reason (R): Carbon can form strong covalent bonds and shows catenation.
Answer: (A)
Assertion (A): Covalent compounds generally have low melting and boiling points.
Reason (R): Covalent compounds do not contain free ions.
Answer: (B)
Assertion (A): Methane burns in air to form carbon dioxide and water.
Reason (R): Methane is a saturated hydrocarbon that undergoes complete combustion.
Answer: (A)
Assertion (A): Graphite conducts electricity.
Reason (R): Graphite has free electrons that can move between its layers.
Answer: (A)
Assertion (A): Saturated hydrocarbons undergo substitution reactions.
Reason (R): In saturated hydrocarbons, all bonds are single and can be replaced by other atoms under specific conditions.
Answer: (A)
Assertion (A): Ethene is more reactive than ethane.
Reason (R): Ethene has a double bond which is more reactive than a single bond.
Answer: (A)
Assertion (A): Covalent compounds conduct electricity in aqueous solution.
Reason (R): Covalent compounds form ions in water.
Answer: (D)
Assertion (A): Carbon forms four covalent bonds with other atoms.
Reason (R): Carbon has four valence electrons and needs four more to complete its octet.
Answer: (A)
Assertion (A): Soap does not work well with hard water.
Reason (R): Hard water contains calcium and magnesium ions that form insoluble salts with soap.
Answer: (A)
Assertion (A): Vinegar is used as a preservative.
Reason (R): It contains acetic acid which is a weak acid but inhibits microbial growth.
Answer: (A)
Assertion (A): Ethanol reacts with sodium to release hydrogen gas.
Reason (R): Alcohols contain hydroxyl groups that react with active metals like sodium.
Answer: (A
Assertion (A): Soaps form scum in hard water.
Reason (R): Scum is formed due to reaction between soap and calcium/magnesium ions.
Answer: (A)
Assertion (A): Detergents are more effective than soaps in hard water.
Reason (R): Detergents form soluble salts with calcium and magnesium ions.
Answer: (A)
Assertion (A): Homologous series have similar chemical properties.
Reason (R): They have the same functional group and differ by a CH₂ unit.
Answer: (A)
Assertion (A): Ethanoic acid has a sour taste and turns blue litmus red.
Reason (R): It is a weak acid and partially dissociates in water.
Answer: (A)
Assertion (A): Butyne is a saturated hydrocarbon.
Reason (R): It contains a triple bond between carbon atoms.
Answer: (D)
Assertion (A): Micelles are formed when soap is added to water.
Reason (R): Soap molecules have hydrophilic and hydrophobic ends.
Answer: (A)
Assertion (A): Carbon does not form ionic compounds.
Reason (R): Carbon cannot gain or lose four electrons easily.
Answer: (A)
Assertion (A): Functional groups determine the properties of organic compounds.
Reason (R): Functional groups are the reactive parts of a molecule.
Answer: (A)
Assertion (A): Ethanol shows acidic behavior in water.
Reason (R): It releases H⁺ ions in aqueous solution.
Answer: (C)
Assertion (A): Carbon forms covalent bonds with other atoms.
Reason (R): Carbon has four electrons in its outermost shell.
Answer: (C)
Assertion (A): Diamond is the hardest natural substance.
Reason (R): In diamond, each carbon atom is bonded to four other carbon atoms in a tetrahedral structure.
Answer: (A)
Assertion (A): Graphite is a good conductor of electricity.
Reason (R): Graphite has delocalized electrons between its layers.
Answer: (A
Assertion (A): Methane is a saturated hydrocarbon.
Reason (R): Methane has only single bonds between carbon atoms.
Answer: (A)
Assertion (A): Ethene is more reactive than ethane.
Reason (R): Ethene contains a double bond which is more reactive than the single bond in ethane.
Answer: (A)
Assertion (A): Soap forms scum in hard water.
Reason (R): Soap reacts with calcium and magnesium ions to form insoluble salts.
Answer: (A)
Assertion (A): Detergents do not form scum in hard water.
Reason (R): Detergents form soluble salts with calcium and magnesium ions.
Answer: (A)
Assertion (A): Alcohols contain hydroxyl (-OH) group.
Reason (R): Hydroxyl group is responsible for the chemical properties of alcohols.
Answer: (A)
Assertion (A): Ethanol reacts with sodium metal to release hydrogen gas.
Reason (R): Sodium displaces hydrogen from ethanol due to its high reactivity.
Answer: (A)
Assertion (A): Vinegar is a solution of acetic acid in water.
Reason (R): Acetic acid is a strong acid that completely ionizes in water.
Answer: (D)
Assertion (A): Carbon can form chains and rings due to catenation.
Reason (R): Carbon atoms can form strong covalent bonds with other carbon atoms.
Answer: (A)
Assertion (A): Carbon compounds generally have low melting and boiling points.
Reason (R): Carbon compounds are covalent and have weak intermolecular forces.
Answer: (A)
Assertion (A): Functional groups determine the properties of organic compounds.
Reason (R): Functional groups are the reactive parts of the molecules.
Answer: (A)
Assertion (A): Alcohols and carboxylic acids are soluble in water.
Reason (R): They form hydrogen bonds with water molecules.
Answer: (A)
Assertion (A): Ethene undergoes addition reactions.
Reason (R): Double bonds in ethene can open to add atoms.
Answer: (A)
Assertion (A): Carbon does not form ionic bonds easily.
Reason (R): It has intermediate electronegativity and forms covalent bonds.
Answer: (A)
Assertion (A): In soap, the hydrophobic tail interacts with grease, and the hydrophilic head interacts with water.
Reason (R): This dual nature helps in cleaning.
Answer: (A)
Assertion (A): Carbon dioxide is acidic in nature.
Reason (R): Carbon dioxide reacts with water to form carbonic acid.
Answer: (A)
Assertion (A): Saturated hydrocarbons do not react with bromine water in the dark.
Reason (R): They lack double bonds that add bromine.
Answer: (A)
Assertion (A): Diamond does not conduct electricity.
Reason (R): All electrons in diamond are involved in covalent bonds.
Answer: (A)
Assertion and Reason Questions Class 10 Science – Practice with Best Answers
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