ROUTERA

Chemical Reactions and Equations

Class 10th Science Chapter Assertion and Reason

Chemical Reactions and Equations

  • Options:
    a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
    b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
    c) Assertion (A) is true, but Reason (R) is false.
    d) Assertion (A) is false, but Reason (R) is true.

Question 1

Assertion (A): A chemical reaction involves the formation of new substances.
Reason (R): During a chemical reaction, bonds between atoms are broken and formed.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Chemical reactions involve the rearrangement of atoms, resulting in the formation of new substances with different properties, which occurs due to the breaking and forming of chemical bonds.

Question 2

Assertion (A): The law of conservation of mass states that mass can be created or destroyed in a chemical reaction.
Reason (R): In a chemical reaction, the total mass of reactants is equal to the total mass of products.

  • Answer: b) Assertion (A) is false, but Reason (R) is true.
  • Explanation: The law of conservation of mass states that mass cannot be created or destroyed, meaning that the mass of reactants before a reaction is equal to the mass of products after the reaction. Therefore, Assertion (A) is incorrect.

Question 3

Assertion (A): Combustion reactions always require oxygen.
Reason (R): Combustion is the process of burning a substance to release energy.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Combustion reactions involve the reaction of a substance with oxygen to produce energy, typically in the form of heat and light.

Question 4

Assertion (A): Oxidation is the process of gaining electrons.
Reason (R): Oxidation results in an increase in the oxidation state of an element.

  • Answer: b) Assertion (A) is false, but Reason (R) is true.
  • Explanation: Oxidation is defined as the loss of electrons, which leads to an increase in the oxidation state of an element. Therefore, Assertion (A) is incorrect.

Question 5

Assertion (A): All chemical reactions can be represented by a chemical equation.
Reason (R): A chemical equation shows the reactants and products of a reaction in terms of their symbols and formulas.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Chemical equations provide a concise representation of chemical reactions, indicating the reactants that undergo change and the products that are formed.

Question 6

Assertion (A): A double displacement reaction involves the exchange of ions between two reactants.
Reason (R): In a double displacement reaction, two compounds react to form two new compounds.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Double displacement reactions involve the swapping of ions between two compounds, resulting in the formation of two new compounds.

Question 7

Assertion (A): Endothermic reactions absorb heat from their surroundings.
Reason (R): The energy of the products in an endothermic reaction is greater than that of the reactants.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: In endothermic reactions, heat is absorbed, resulting in products that have higher energy than the reactants.

Question 8

Assertion (A): A catalyst is a substance that increases the rate of a chemical reaction without being consumed.
Reason (R): Catalysts lower the activation energy required for a reaction to occur.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Catalysts facilitate reactions by providing an alternative pathway with a lower activation energy, allowing the reaction to proceed faster while remaining unchanged at the end.

Question 9

Assertion (A): Neutralization reactions always produce salt and water.
Reason (R): In neutralization, an acid reacts with a base to form products that neutralize the pH.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Neutralization involves the reaction between an acid and a base, resulting in the formation of salt and water, which balances the pH of the solution.

Question 10

Assertion (A): In a redox reaction, one reactant gets oxidized while another gets reduced.
Reason (R): Oxidation and reduction always occur simultaneously in a chemical reaction.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Redox (reduction-oxidation) reactions involve the transfer of electrons, where one substance is oxidized (loses electrons) and another is reduced (gains electrons), ensuring that both processes happen concurrently.

Question 11

Assertion (A): Decomposition reactions involve a single reactant breaking down into two or more products.
Reason (R): Decomposition reactions require heat, light, or electricity to proceed.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Decomposition reactions involve a single compound breaking down into simpler substances, and they typically require energy in the form of heat, light, or electricity to initiate the process.

Question 12

Assertion (A): A precipitate is formed in a chemical reaction when two solutions react.
Reason (R): A precipitate is an insoluble solid that forms during a chemical reaction in a solution.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: When two soluble reactants combine and produce an insoluble product, this solid forms and is known as a precipitate, indicating a chemical change has occurred.

Question 13

Assertion (A): The reaction between an acid and a metal produces hydrogen gas.
Reason (R): Metals react with acids to form salts and hydrogen gas, which is often observed as bubbles.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: When acids react with reactive metals, they displace hydrogen, leading to the formation of hydrogen gas and a salt, which is observable as effervescence.

Question 14

Assertion (A): Synthesis reactions involve the combination of two or more substances to form a single product.
Reason (R): Synthesis reactions are always exothermic and release energy.

  • Answer: b) Assertion (A) is true, but Reason (R) is false.
  • Explanation: While synthesis reactions do result in a single product from multiple reactants, they can be either exothermic (releasing energy) or endothermic (absorbing energy), depending on the specific substances involved.

Question 15

Assertion (A): The formation of rust is a type of oxidation reaction.
Reason (R): Rusting occurs when iron reacts with oxygen in the presence of moisture.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Rusting is indeed an oxidation process where iron reacts with oxygen in the presence of water or moisture, leading to the formation of iron oxide (rust).

Question 16

Assertion (A): The chemical equation for a reaction must be balanced to comply with the law of conservation of mass.
Reason (R): Balancing a chemical equation ensures that the number of atoms for each element is the same on both sides of the equation.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: According to the law of conservation of mass, the total mass of reactants must equal the total mass of products. Balancing the equation maintains equal numbers of each type of atom on both sides.

Question 17

Assertion (A): Sodium bicarbonate reacts with acetic acid to produce carbon dioxide gas.
Reason (R): This reaction is an example of a neutralization reaction.

  • Answer: b) Assertion (A) is true, but Reason (R) is false.
  • Explanation: The reaction between sodium bicarbonate (baking soda) and acetic acid (vinegar) produces carbon dioxide gas, water, and sodium acetate, but it is not a typical neutralization reaction since it involves a weak acid and a bicarbonate base.

Question 18

Assertion (A): Chemical reactions can occur at different rates depending on various factors.
Reason (R): Factors like concentration, temperature, and presence of a catalyst affect the rate of a reaction.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: The rate of a chemical reaction can indeed vary based on concentration, temperature, and whether a catalyst is present, affecting how quickly reactants are converted into products.

Question 19

Assertion (A): Electrolysis is a method used to carry out decomposition reactions.
Reason (R): Electrolysis involves passing an electric current through a substance to break it down into simpler products.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: Electrolysis is a specific method of decomposition where electrical energy is used to break down compounds, such as water into hydrogen and oxygen.

Question 20

Assertion (A): Acid-base reactions are characterized by the formation of water and salt.
Reason (R): The products of acid-base reactions result from the neutralization process.

  • Answer: a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  • Explanation: In acid-base neutralization reactions, an acid reacts with a base to produce salt and water, which is a defining characteristic of such reactions.