Assertion and Reason set based on NCERT Class 10 Science Chapter 1: Chemical Reactions and Equations.

Assertion and Reason set based on NCERT Class 10 Science Chapter 1: Chemical Reactions and Equations.
Assertion and Reason Type Questions
Each question consists of an Assertion (A) and a Reason (R). Choose the correct option:
- (A) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
- (B) Both the Assertion and the Reason are correct, but the Reason does not properly explain the Assertion.
- (C) Assertion is true, but Reason is false.
- (D) Assertion is false, but Reason is true.

Basic Concepts of Chemical Reactions
- (A): A chemical equation must be balanced.
(R): A balanced chemical equation follows the law of conservation of mass. - (A): A balanced chemical equation represents the actual number of atoms involved in a reaction.
(R): The mass of reactants and products must be equal in a chemical reaction. - (A): A chemical reaction occurs when reactants are converted into products.
(R): During a reaction, chemical bonds in reactants are broken and new bonds are formed to create products. - (A): Magnesium ribbon is cleaned before burning in air.
(R): Magnesium reacts with atmospheric oxygen and forms a protective oxide layer that must be removed before burning. - (A): Chemical reactions always produce a gas.
(R): All chemical reactions result in a change in physical state.
Types of Chemical Reactions
- (A): The reaction of sodium with water is highly exothermic.
(R): Sodium reacts with water to form sodium hydroxide and hydrogen gas, releasing heat. - (A): A decomposition reaction requires an external energy source.
(R): Decomposition reactions break down a single compound into two or more simpler substances. - (A): Combination reactions always release energy.
(R): In a combination reaction, two or more substances react to form a single product. - (A): The rusting of iron is an example of a combination reaction.
(R): Rust is formed when iron combines with oxygen and water. - (A): The reaction between iron and copper sulphate is a displacement reaction.
(R): A more reactive metal displaces a less reactive metal from its salt solution. - (A): All decomposition reactions require heat, light, or electricity.
(R): Decomposition reactions break down compounds into simpler substances. - (A): The reaction between barium chloride and sodium sulphate is a double displacement reaction.
(R): This reaction produces a precipitate of barium sulphate. - (A): In an exothermic reaction, heat is absorbed.
(R): Energy is required to break chemical bonds in exothermic reactions. - (A): In a neutralization reaction, heat is always released.
(R): Neutralization reactions involve the combination of acids and bases to form salt and water. - (A): Respiration is an exothermic reaction.
(R): During respiration, glucose is broken down in the presence of oxygen to release energy.
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Oxidation and Reduction
- (A): Rusting of iron is an oxidation reaction.
(R): Iron reacts with oxygen and water to form hydrated iron oxide. - (A): When zinc is added to copper sulphate solution, zinc displaces copper.
(R): Zinc is more reactive than copper in the reactivity series. - (A): A substance that gains oxygen is said to be oxidized.
(R): Oxidation is the process of losing electrons. - (A): Reduction is the gain of hydrogen.
(R): Reduction involves the loss of electrons. - (A): In the reaction
, copper is oxidized.
(R): Hydrogen removes oxygen from copper oxide, forming copper metal. - (A): Photosynthesis is an oxidation-reduction reaction.
(R): Carbon dioxide is reduced to glucose, and water is oxidized to oxygen. - (A): The burning of coal is an oxidation reaction.
(R): Carbon reacts with oxygen to form carbon dioxide, releasing heat. - (A): Corrosion is a redox reaction.
(R): Metals lose electrons when they react with oxygen and water. - (A): Silver articles turn black due to oxidation.
(R): Silver reacts with hydrogen sulphide in the air to form silver sulphide. - (A): The reaction of iron with hydrochloric acid is an example of oxidation.
(R): Iron donates electrons to hydrogen ions, forming iron chloride and hydrogen gas.
Chemical Changes and Applications
- (A): Rancidity occurs when fats and oils react with oxygen.
(R): Flushing food with nitrogen gas prevents rancidity. - (A): Corrosion can be prevented by galvanization.
(R): Galvanization involves coating iron with zinc to prevent rusting. - (A): Precipitation reactions are examples of double displacement reactions.
(R): Precipitation occurs when two aqueous solutions react to form an insoluble solid. - (A): All combination reactions are exothermic.
(R): Some combination reactions, such as the formation of nitric acid, absorb heat. - (A): Fermentation is an oxidation reaction.
(R): Fermentation is a process in which sugars are broken down, resulting in the formation of alcohol and carbon dioxide.
Advanced Concepts
- (A): Decomposition of silver bromide is a photochemical reaction.
(R): Silver bromide breaks down in the presence of sunlight. - (A): The electrolysis of water produces hydrogen and oxygen in a 2:1 ratio.
(R): Water consists of two hydrogen atoms and one oxygen atom. - (A): A catalyst speeds up a reaction by increasing activation energy.
(R): Catalysts provide an alternative pathway with lower activation energy. - (A): The reaction between calcium carbonate and hydrochloric acid produces carbon dioxide.
(R): Acid reacts with carbonate compounds to release CO₂. - (A): When a lead-acid battery is discharged, lead sulphate forms.
(R): Lead sulphate formation is a reversible reaction. - (A): Endothermic reactions absorb heat.
(R): Photosynthesis is an endothermic process. - (A): All redox reactions involve oxidation and reduction occurring simultaneously.
(R): Electrons lost in oxidation are gained in reduction. - (A): A precipitation reaction always produces gas.
(R): Precipitation reactions result in an insoluble solid formation. - (A): Anodizing protects aluminum from corrosion.
(R): Anodizing increases the thickness of the oxide layer on aluminum. - (A): Neutralization reactions always involve an acid and a base.
(R): A neutralization reaction produces salt and water.
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