Class 10 Exam  >  Class 10 Notes  >  Chemistry for Class 10  >  Assertion & Reason Type Questions: Chemical Reactions & Equations - 1

Class 10 Science Chapter 1 Assertion and Reason Questions - Chemical Reactions and Equations

Directions: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Question 1: 
Assertion (A): Carbon dioxide turns lime water milky. 
Reason (R): Carbon dioxide sullies the water.
(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.

Correct Answer is Option (c)

Class 10 Science Chapter 1 Assertion and Reason Questions - Chemical Reactions and Equations

Carbon dioxide reacts with lime water (calcium hydroxide) to form milky precipitate of calcium carbonate.


Question 2:

Assertion (A): After white washing the walls, a shiny white finish on walls is obtained after two to three days.
Reason (R): Calcium oxide reacts with carbon dioxide to form calcium hydrogen carbonate which gives a shiny white finish.

(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.

Correct Answer is Option (c)

Calcium hydroxide is present in whitewash. It reacts slowly with the carbon dioxide in air to form a thin layer of calcium carbonate on the walls. Calcium carbonate is formed after two to three days of white washing. Hence the shiny white finish appears after two to three days on the walls.


Question 3:
Assertion (A): A chemical reaction becomes faster at higher temperatures. 
Reason (R): At higher temperatures, molecular motion becomes more rapid.
(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.

Correct Answer is Option (a)

It is mentioned at the beginning. A chemical reaction becomes faster at higher temperatures because at high temperature, the movement of particles are greater.


Question 4:
Assertion (A): To dilute sulphuric acid, acid is added to water and not water to acid.
Reason (R): Specific heat of water is quite large.
(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.

Correct Answer is Option (a)
The mixing of water to an acid is highly exothermic in nature. If water is added to an acid it produces a very large amount of heat which can break the container and sometimes even causes burning. So it is advised to add concentrated acid to water in a very slow manner.


Question 5:
Assertion (A): Sodium metal is stored under kerosene.
Reason (R): Metallic sodium melts when exposed to air.

(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.

Correct Answer is Option (c)
Sodium is a very reactive metal. It is kept in kerosene to prevent it from coming in contact with oxygen and moisture. If this happens, it will react with the moisture present in air and form sodium hydroxide. This is a strongly exothermic reaction, and a lot of heat is generated.


Question 6:
Assertion: Corrosion of iron is commonly known as rusting. 
Reason: Corrosion of iron occurs in the presence of water and air.
(a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) If Assertion is correct but Reason is incorrect.
(d) If Assertion is incorrect but Reason is correct.

Correct Answer is Option (b)
Iron when exposed to moist air for a long time acquires a coating of a brown flaky substance called rust. Thus, both statements are true but independent of each other.


Question 7:
Assertion: A reducing agent is a substance which can either accept electrons.
Reason: A substance which helps in oxidation is known as a reducing agent.

(a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) If Assertion is correct but Reason is incorrect.
(d) If Assertion is incorrect but Reason is correct.

Correct Answer is Option (d)
A reducing agent is a substance which oxidizes itself but reduces others i.e., loses electrons.


Question 8:
Assertion (A): Carbon dioxide turns lime water milky.
Reason (R): Carbon dioxide sullies the water.

(a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) 
If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) 
If Assertion is correct but Reason is incorrect.
(d) 
If Assertion is incorrect but Reason is correct.

Correct Answer is Option (c)
Assertion (A) is true but reason (R) is false. Carbon dioxide reacts with lime water (calcium hydroxide) to form milky precipitate of calcium carbonate.


Question 9:
Assertion (A): Sodium metal is stored under Kerosene.
Reason (R): Metallic sodium melts when exposed to air.

(a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) 
If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) 
If Assertion is correct but Reason is incorrect.
(d) 
If Assertion is incorrect but Reason is correct.

Correct Answer is Option (c)
Assertion (A) is true but reason (R) is false. Sodium is a very reactive metal. It is kept in kerosene to prevent it from coming in contact with oxygen and moisture present. If this happens, it will react with the moisture present in air and form sodium hydroxide. This is a strongly exothermic reaction, and a lot of heat is generated.


Question 10:
Assertion(A): Calcium corbonate when heated gives calcium oxide and water.
Reason (R): On heating calcium carbonate, decomposition reaction takes place.

(a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) If Assertion is correct but Reason is incorrect.
(d) If Assertion is incorrect but Reason is correct.

Correct Answer is Option (d)
On heating calcium carbonate, calcium oxide and carbon dioxide are formed.


Question 11:
Assertion(A): White silver chloride turns grey in sunlight.
Reason (R): Decomposition of silver chloride in presence of sunlight takes place to form silver metal and chlorine gas.

(a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) If Assertion is correct but Reason is incorrect.
(d) If Assertion is incorrect but Reason is correct.

Correct Answer is Option (a)
Silver chloride turns grey when kept in sunlight. This is because a photolytic decomposition reaction takes place where the white silver chloride decomposes in the presence of sunlight to form white silver and chlorine gas which escapes.

Decomposition of silver chloride Decomposition of silver chloride 


Question 12:
Assertion(A): In a reaction of copper with oxygen, copper serves as a reducing agent. 
Reason (R): The substance which gains oxygen in a chemical reaction is a reducing agents. 
(a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) If Assertion is correct but Reason is incorrect.
(d) If Assertion is incorrect but Reason is correct.

Correct Answer is Option (a)
Both A and R are true and R is the correct explanation of A.


Question 13: 
Assertion: Fe2O3 + 2Al → Al2O3 + 2Fe 
The above chemical equation is an example of displacement reaction. 
Reason: Aluminium  being more reactive than iron, displaces Fe from its oxide
(a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) If Assertion is correct but Reason is incorrect.
(d) If Assertion is incorrect but Reason is correct.

Correct Answer is Option (a)
Fe2O3 + 2Al → Al2O3 + 2Fe is a displacement reaction, Here, a highly reactive element (Al) displaces Fe from Fe2O3.


Question 14:
Assertion: Quicklime reacts vigorously with water releasing a large amount of heat. Reason: The above chemical reaction is an exothermic reaction.
(a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) If Assertion is correct but Reason is incorrect.
(d) If Assertion is incorrect but Reason is correct.

Correct Answer is Option (a)
If both Assertion and Reason are true and Reason is the correct explanation of Assertion. Because in exothermic reactions, hear is released along with the formation of products.


Question 15: 
Assertion: Photosynthesis is considered as an endothermic reaction.
Reason: Energy gets released in the process of photosynthesis.

(a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) 
If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) 
If Assertion is correct but Reason is incorrect.
(d)
If Assertion is incorrect but Reason is correct.

Correct Answer is Option (c)
If Assertion is true, but Reason is false. Photosynthesis is considered as an endothermic reaction because energy in the form of sunlight is absorbed by the green plants.

The document Class 10 Science Chapter 1 Assertion and Reason Questions - Chemical Reactions and Equations is a part of the Class 10 Course Chemistry for Class 10.
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FAQs on Class 10 Science Chapter 1 Assertion and Reason Questions - Chemical Reactions and Equations

1. What is a chemical reaction?
Ans. A chemical reaction is a process in which one or more substances are converted into different substances with new chemical properties. During a chemical reaction, bonds between atoms are broken and new bonds are formed, resulting in the rearrangement of atoms to create new molecules.
2. How are chemical reactions represented?
Ans. Chemical reactions are represented using chemical equations. In a chemical equation, the reactants (substances that undergo the reaction) are written on the left side of the equation and the products (substances formed as a result of the reaction) are written on the right side. The reactants and products are separated by an arrow, indicating the direction of the reaction.
3. What are the different types of chemical reactions?
Ans. There are several types of chemical reactions, including: - Combination or synthesis reaction: Two or more substances combine to form a single product. - Decomposition reaction: A single compound breaks down into two or more simpler substances. - Displacement or substitution reaction: An element reacts with a compound, displacing another element from it. - Double displacement or metathesis reaction: Two compounds exchange ions to form new compounds. - Redox or oxidation-reduction reaction: Involves the transfer of electrons between reactants.
4. What is the importance of balancing chemical equations?
Ans. Balancing chemical equations is important because it ensures that the law of conservation of mass is obeyed. The law of conservation of mass states that matter cannot be created or destroyed in a chemical reaction, only rearranged. Balancing the equation means that the number of atoms of each element is the same on both sides of the equation, indicating that mass is conserved.
5. How can chemical reactions be classified based on energy changes?
Ans. Chemical reactions can be classified into exothermic and endothermic reactions based on energy changes. - Exothermic reactions release energy in the form of heat, light, or sound. The products have less energy than the reactants, and the reaction is usually accompanied by a rise in temperature. - Endothermic reactions absorb energy from the surroundings. The products have more energy than the reactants, and the reaction is usually accompanied by a decrease in temperature.
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