Difference Between Bleaching Powder and Sodium Hydroxide (with Table)
Bleaching powder and sodium hydroxide are essential in chemistry and help students understand various practical and theoretical applications related to this topic. Both compounds play a vital role in industries and daily life, making them important for exams and real-world problem-solving.
What is Bleaching Powder and Sodium Hydroxide in Chemistry?
A bleaching powder and sodium hydroxide refers to two commonly used inorganic compounds in applied and industrial chemistry. These topics appear in chapters related to acids, bases and salts, environmental chemistry, and chemical industries, making them a foundational part of your chemistry syllabus.
Molecular Formula and Composition
The molecular formula of bleaching powder is Ca(OCl)2 and for sodium hydroxide is NaOH. Bleaching powder consists of calcium, oxygen, and chlorine and is categorized as an oxychloride. Sodium hydroxide is made up of sodium cations and hydroxide anions, classifying it as a strong base (alkali).
| Compound | Chemical Name | Formula | Classification |
|---|---|---|---|
| Bleaching Powder | Calcium Oxychloride (Calcium Hypochlorite) | Ca(OCl)2 | Disinfectant, Bleaching agent |
| Sodium Hydroxide | Caustic Soda | NaOH | Strong Alkali (Base) |
Preparation and Synthesis Methods
The preparation of bleaching powder and sodium hydroxide relies on key industrial chemical processes:
| Compound | Preparation Method | Key Equation |
|---|---|---|
| Bleaching Powder | Reaction of chlorine gas with dry slaked lime | Ca(OH)2 + Cl2 → Ca(OCl)2 + H2O |
| Sodium Hydroxide | Electrolysis of brine solution (Chloralkali process) | 2NaCl + 2H2O → 2NaOH + Cl2 + H2 |
Physical Properties of Bleaching Powder and Sodium Hydroxide
- Bleaching powder is a pale yellowish-white powder with a sharp chlorine odor. It is slightly soluble in water, leaving behind an insoluble residue.
- Sodium hydroxide appears as white pellets, flakes, or solid. It is very soluble in water, forming a slippery, strongly alkaline solution that can corrode organic materials and glass.
Chemical Properties and Reactions
Bleaching powder acts as an oxidizing and bleaching agent. It releases chlorine when treated with dilute acids. Sodium hydroxide is a strong base, forming salts upon neutralization with acids and saponifying fats in the soap-making process.
Frequent Related Errors
- Confusing bleaching powder with neutral molecules or with sodium hypochlorite (liquid bleach).
- Mixing up sodium hydroxide with sodium chloride or other sodium compounds.
- Ignoring the release of chlorine gas when bleach reacts with acids or bases.
- Overlooking the strong caustic nature and safety risks of both chemicals.
Uses of Bleaching Powder and Sodium Hydroxide in Real Life
Bleaching powder and sodium hydroxide have widespread applications:
- Disinfecting drinking water and public pools (bleaching powder)
- Textile and paper bleaching (bleaching powder)
- Household cleaning and laundry (both compounds)
- Soap and detergent manufacturing (sodium hydroxide)
- Caustic washing in the petroleum industry (sodium hydroxide)
- Making rayon and processing aluminum ore (sodium hydroxide)
Relevance in Competitive Exams
Students preparing for NEET, JEE, and Olympiads should be familiar with bleaching powder and sodium hydroxide, as these compounds often feature in reaction-based, preparation, and conceptual MCQ or theory questions.
Relation with Other Chemistry Concepts
Bleaching powder and sodium hydroxide are closely related to topics such as chemical reactions, acids and bases, and water purification. They help students build a conceptual bridge between industrial chemistry, environmental safety, and practical laboratory applications.
Step-by-Step Reaction Example
1. Preparation of bleaching powder:Ca(OH)2 + Cl2 → Ca(OCl)2 + H2O
2. Explanation:
- Dry slaked lime (calcium hydroxide) reacts with chlorine gas at around 40°C.
- The reaction yields bleaching powder (calcium oxychloride) and water as a by-product.
3. Reaction between sodium hydroxide and chlorine gas (for reference):
2NaOH + Cl2 → NaCl + NaClO + H2O
- Chlorine reacts with concentrated sodium hydroxide to form sodium chloride, sodium hypochlorite, and water.
Lab or Experimental Tips
Remember that bleaching powder must be stored in airtight containers and away from moisture, as it decomposes to release chlorine. Sodium hydroxide (caustic soda) should always be handled with gloves since it is corrosive. Vedantu educators often highlight never to directly mix bleach and alkali as this can release hazardous chlorine gas.
Try This Yourself
- Write the IUPAC name and formula of bleaching powder and sodium hydroxide.
- Explain why sodium hydroxide feels soapy but is highly caustic.
- Give two examples of industry or household uses for each compound.
Final Wrap-Up
We explored bleaching powder and sodium hydroxide—their structure, formulas, preparation, properties, uses, and significance in chemistry and industry. For detailed explanations and free tutoring on this topic, join live classes and revision sessions at Vedantu. Build your strong foundation for board exams and competitive tests!
FAQs on Bleaching Powder and Sodium Hydroxide: Chemistry, Reactions & Uses
1. What is the chemical formula of bleaching powder?
The chemical formula for bleaching powder, also known as calcium hypochlorite, is Ca(OCl)₂. It's an inorganic compound commonly used as a bleaching agent and disinfectant.
2. What happens when you mix sodium hydroxide with bleach?
Mixing sodium hydroxide (NaOH) with bleach (typically sodium hypochlorite, NaOCl) can produce hazardous reactions. It can release toxic chlorine gas (Cl₂), which is extremely dangerous. This reaction should never be attempted outside of a controlled laboratory setting with proper safety precautions.
3. What are the uses of bleaching powder?
Bleaching powder has several important uses:
- Water treatment: Disinfection of drinking water and swimming pools.
- Textile industry: Bleaching cotton and linen fabrics.
- Household cleaning: Used as a disinfectant and bleaching agent.
- Pulp and paper industry: Bleaching wood pulp.
4. Is sodium hydroxide compatible with bleach?
No, sodium hydroxide and bleach are incompatible. Mixing them can lead to the formation of toxic chlorine gas and other hazardous substances. It's crucial to avoid mixing these chemicals.
5. How is bleaching powder prepared?
Bleaching powder is industrially prepared by reacting chlorine gas (Cl₂) with dry slaked lime [Ca(OH)₂]. The reaction is: Ca(OH)₂ + Cl₂ → Ca(OCl)₂ + H₂O
6. What is the chemical name and formula of sodium hydroxide?
The chemical name is sodium hydroxide, and its formula is NaOH. It is also known as caustic soda.
7. What are the main uses of sodium hydroxide?
Sodium hydroxide (NaOH) has numerous applications, including:
- Soap and detergent production: Saponification of fats and oils.
- Paper manufacturing: Used in the pulping process.
- Metal processing: Cleaning and degreasing metals.
- Drain cleaners: A common component in commercial drain cleaners.
- Chemical synthesis: Used in various chemical reactions.
8. How is sodium hydroxide manufactured?
Sodium hydroxide is primarily produced through the chlor-alkali process, which involves the electrolysis of brine (a concentrated solution of sodium chloride, NaCl). This process simultaneously generates chlorine gas (Cl₂) and hydrogen gas (H₂) as byproducts.
9. What safety precautions should be taken when handling bleaching powder and sodium hydroxide?
Both bleaching powder and sodium hydroxide are corrosive and can cause severe burns. Always wear appropriate protective gear, including gloves, eye protection, and a lab coat. Handle in a well-ventilated area to avoid inhaling any fumes. Follow proper disposal procedures for these chemicals.
10. What are the differences between bleaching powder and sodium hydroxide?
Bleaching powder [Ca(OCl)₂] is a bleaching agent and disinfectant, while sodium hydroxide (NaOH) is a strong base used in many industrial processes. Bleaching powder is a salt, while sodium hydroxide is an alkali. They have different chemical properties and uses. Mixing them is hazardous.
11. What is the role of chlorine in the preparation of bleaching powder?
Chlorine gas (Cl₂) is a crucial reactant in the preparation of bleaching powder. It reacts with slaked lime [Ca(OH)₂] to form calcium hypochlorite [Ca(OCl)₂], the main component of bleaching powder.
12. Why is sodium hydroxide known as caustic soda?
Sodium hydroxide (NaOH) is called caustic soda because it's highly corrosive (caustic) and has a somewhat soapy texture reminiscent of traditional soda.
