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Practice Class 10 Science Chapter 2 – Acids, Bases and Salts with 5 NCERT-based MCQs on bleaching powder, its preparation, chemical formula, properties, uses and reactions with dilute acids.
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Chapter Information
Subject: Science
Class: 10
Chapter: Acids, Bases and Salts
Question Type: Multiple Choice Questions (MCQs)
Practice Set: 8
Difficulty Level: Moderate
Based On: NCERT Syllabus
Introduction
Bleaching powder is an important compound discussed in Class 10 Science Chapter 2. It is widely used for disinfecting drinking water and in several industrial processes.
Bleaching powder is prepared by passing chlorine gas over dry slaked lime. Understanding its preparation, chemical formula, properties and uses is important for NCERT-based examinations.
This Practice Set 8 focuses on bleaching powder, its preparation, chemical formula, important uses and its reaction with dilute acids.
What You Will Learn
✔ Bleaching powder
✔ Chemical formula of bleaching powder
✔ Preparation of bleaching powder
✔ Role of chlorine in bleaching powder
✔ Uses of bleaching powder
✔ Reaction of bleaching powder with dilute acids
✔ Disinfection of drinking water
Why This Topic Is Important
Bleaching powder is an important salt with several practical applications. NCERT questions can ask about its preparation, formula, uses and chemical reactions.
Students should especially remember that bleaching powder is used for disinfecting drinking water and that chlorine is released when it reacts with dilute acids.
5 MCQs with Answers and Detailed Solutions
Q1. What is the chemical formula commonly used to represent bleaching powder?
A) CaCO₃
B) CaOCl₂
C) Ca(OH)₂
D) NaCl
Answer: B) CaOCl₂
Detailed Solution
Bleaching powder is commonly represented by the chemical formula:
CaOCl₂
It is prepared by passing chlorine gas over dry slaked lime.
The reaction can be represented as:
Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O
Therefore, the correct answer is B) CaOCl₂.
Exam Tip
Remember:
Bleaching powder → CaOCl₂
Q2. Which substance is used to prepare bleaching powder?
A) Dry slaked lime
B) Sodium chloride
C) Sodium hydroxide
D) Calcium carbonate
Answer: A) Dry slaked lime
Detailed Solution
Bleaching powder is prepared by passing chlorine gas over dry slaked lime.
The reaction is represented as:
Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O
Here, calcium hydroxide or slaked lime reacts with chlorine to form bleaching powder.
Therefore, the correct answer is A) Dry slaked lime.
Exam Tip
Remember:
Chlorine + Dry slaked lime → Bleaching powder
Q3. Which of the following is an important use of bleaching powder?
A) Disinfecting drinking water
B) Producing cooking oil
C) Making petrol
D) Producing nitrogen gas
Answer: A) Disinfecting drinking water
Detailed Solution
Bleaching powder is commonly used for disinfecting drinking water because it releases substances that help kill harmful microorganisms.
It is also used for bleaching cotton and linen in the textile industry and for bleaching wood pulp in the paper industry.
Therefore, the correct answer is A) Disinfecting drinking water.
Exam Tip
Important uses:
Water disinfection + Textile bleaching + Paper industry
Q4. What happens when bleaching powder reacts with dilute hydrochloric acid?
A) Oxygen is released
B) Chlorine gas is released
C) Hydrogen gas is released
D) Nitrogen gas is released
Answer: B) Chlorine gas is released
Detailed Solution
Bleaching powder reacts with dilute hydrochloric acid and releases chlorine gas.
A simplified representation is:
CaOCl₂ + 2HCl → CaCl₂ + H₂O + Cl₂
The chlorine released is responsible for the characteristic bleaching and disinfecting action.
Therefore, the correct answer is B) Chlorine gas is released.
Exam Tip
Remember:
Bleaching powder + Dilute HCl → Chlorine gas
Q5. Which property of bleaching powder makes it useful for disinfecting water?
A) It releases chlorine that helps destroy harmful microorganisms
B) It produces hydrogen gas
C) It increases the hardness of water
D) It produces sodium chloride
Answer: A) It releases chlorine that helps destroy harmful microorganisms
Detailed Solution
Bleaching powder can release chlorine, which has strong disinfecting properties.
The chlorine helps destroy many harmful microorganisms present in water, making bleaching powder useful for water treatment.
Therefore, the correct answer is A.
Exam Tip
Remember:
Chlorine → Disinfection → Drinking water treatment
Important Concepts
1. Bleaching Powder
Bleaching powder is commonly represented by:
CaOCl₂
It is prepared by passing chlorine gas over dry slaked lime.
2. Preparation
The preparation can be represented as:
Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O
Here:
- Ca(OH)₂ = Slaked lime
- Cl₂ = Chlorine
- CaOCl₂ = Bleaching powder
3. Uses of Bleaching Powder
Bleaching powder is used for:
- Disinfecting drinking water
- Bleaching cotton and linen
- Bleaching wood pulp
- Certain chemical processes
4. Reaction with Dilute Hydrochloric Acid
Bleaching powder reacts with dilute hydrochloric acid and releases chlorine:
CaOCl₂ + 2HCl → CaCl₂ + H₂O + Cl₂
This reaction is important for understanding the chemical behaviour of bleaching powder.
5. Bleaching Action
The bleaching and disinfecting properties are associated with the chlorine released from bleaching powder.
This makes bleaching powder useful in textile, paper and water-treatment applications.
Related Practice Questions
Q1. What is the formula of bleaching powder?
Q2. How is bleaching powder prepared?
Q3. Why is bleaching powder used for disinfecting drinking water?
Q4. What gas is released when bleaching powder reacts with dilute HCl?
Q5. Name two industrial uses of bleaching powder.
Mini Quiz Challenge
Try answering these questions within 60 seconds.
Q1. Bleaching powder is commonly represented by:
A) CaO
B) CaOCl₂
C) CaCO₃
D) NaHCO₃
Q2. Which gas is used to prepare bleaching powder?
A) Oxygen
B) Hydrogen
C) Chlorine
D) Nitrogen
Q3. Chlorine is passed over:
A) Dry slaked lime
B) Sodium chloride crystals
C) Calcium carbonate
D) Sodium hydroxide crystals
Q4. Which is a major use of bleaching powder?
A) Disinfecting drinking water
B) Producing petrol
C) Making fertilisers only
D) Producing hydrogen
Q5. Which gas is released when bleaching powder reacts with dilute HCl?
A) O₂
B) H₂
C) N₂
D) Cl₂
Exam Tips
✔ Remember the formula CaOCl₂.
✔ Learn that bleaching powder is prepared using chlorine and dry slaked lime.
✔ Remember its use in disinfecting drinking water.
✔ Learn its applications in the textile and paper industries.
✔ Remember that dilute hydrochloric acid can release chlorine from bleaching powder.
✔ Do not confuse bleaching powder with slaked lime.
Quick Revision Notes
✔ Bleaching powder: Commonly represented as CaOCl₂
✔ Preparation: Chlorine + Dry slaked lime
✔ Equation: Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O
✔ Important use: Disinfection of drinking water
✔ Other uses: Bleaching cotton, linen and wood pulp
✔ With dilute HCl: Chlorine gas is released
✔ Important gas: Chlorine (Cl₂)
Common Mistakes Students Make
❌ Confusing bleaching powder with calcium hydroxide.
❌ Forgetting that chlorine is used in its preparation.
❌ Writing oxygen instead of chlorine as the gas released with dilute HCl.
❌ Forgetting its use in water disinfection.
❌ Confusing the formula of bleaching powder with calcium carbonate.
❌ Forgetting the role of chlorine in bleaching and disinfecting.
Key Takeaways
✔ Bleaching powder is commonly represented by CaOCl₂.
✔ It is prepared by passing chlorine over dry slaked lime.
✔ It is widely used to disinfect drinking water.
✔ It is also used for bleaching cotton, linen and wood pulp.
✔ Reaction with dilute hydrochloric acid releases chlorine gas.
✔ Chlorine is responsible for important bleaching and disinfecting properties.
FAQs
Q. What is the formula of bleaching powder?
Answer:
Bleaching powder is commonly represented by CaOCl₂.
Q. How is bleaching powder prepared?
Answer:
It is prepared by passing chlorine gas over dry slaked lime.
Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O
Q. Why is bleaching powder used in drinking water?
Answer:
It releases chlorine, which helps destroy harmful microorganisms and therefore acts as a disinfectant.
Q. What happens when bleaching powder reacts with dilute HCl?
Answer:
It releases chlorine gas.
CaOCl₂ + 2HCl → CaCl₂ + H₂O + Cl₂
Q. Where is bleaching powder used?
Answer:
It is used for disinfecting drinking water, bleaching cotton and linen, and bleaching wood pulp in the paper industry.
Conclusion
Class 10 Science Chapter 2 – Acids, Bases and Salts covers the important NCERT topic of bleaching powder. The set explains its formula, preparation, chemical reaction with dilute hydrochloric acid and major uses.
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