What Is Sodium Hypochlorite? Definition, Structure & Common Questions
Sodium hypochlorite is essential in chemistry and helps students understand various practical and theoretical applications related to this topic. This compound is commonly found in household bleach and is used for disinfection, cleaning, and many industrial processes. Knowing about sodium hypochlorite aids in understanding chemical reactions, safety, and its wide use in everyday life.
What is Sodium Hypochlorite in Chemistry?
A sodium hypochlorite is a chemical compound with the formula NaOCl. In chemistry, it is the main component of liquid bleach and is recognized for its strong oxidizing, disinfectant, and bleaching properties. This concept appears in chapters related to oxidation and reduction, chemical reactions, and industrial chemistry, making it a foundational part of your chemistry syllabus.
Molecular Formula and Composition
The molecular formula of sodium hypochlorite is NaOCl. It consists of one sodium (Na) atom, one oxygen (O) atom, and one chlorine (Cl) atom. Sodium hypochlorite is an ionic compound, containing sodium ions (Na+) and hypochlorite ions (OCl-), placing it in the category of inorganic salts.
Preparation and Synthesis Methods
Sodium hypochlorite is produced both industrially and in the laboratory. The main industrial method involves reacting chlorine gas (Cl2) with cold, dilute sodium hydroxide (NaOH) solution:
Cl2 + 2NaOH → NaCl + NaOCl + H2O
Another approach uses bleaching powder or by electrolysis of brine (concentrated NaCl solution). Laboratory methods often use these same reactions on a smaller scale.
Physical Properties of Sodium Hypochlorite
Sodium hypochlorite is most often used as a pale greenish-yellow liquid solution, but it also exists as a greenish-yellow solid in its pentahydrate form. Here are some important physical properties:
| Property | Value |
|---|---|
| Molar Mass | 74.4 g/mol |
| Color | Greenish-yellow |
| Melting Point (solid pentahydrate) | 18°C |
| Boiling Point (solution) | 101°C |
| Density (solution) | 1.11 g/cm3 |
| Solubility in Water | Very soluble |
| Odor | Chlorine-like, sweetish |
| pH (in solution) | 11–13 (strongly alkaline) |
Chemical Properties and Reactions
Sodium hypochlorite shows powerful oxidizing behavior. It reacts with acids to produce toxic chlorine gas and forms hypochlorous acid in water. Key reactions include:
- Decomposition: 3NaOCl → 2NaCl + NaClO3
- With acids: NaOCl + HCl → NaCl + HOCl (can further generate Cl2 gas)
- With ammonia: Forms chloramines, e.g., NH3 + NaOCl → NH2Cl + NaOH
- Oxidizes metals, organic stains, and microbes
Frequent Related Errors
- Confusing sodium hypochlorite with sodium chlorate or sodium chloride.
- Mixing up sodium hypochlorite’s formula (NaOCl) with that of bleach powders or other oxidizers.
- Assuming all bleach contains only sodium hypochlorite (some use hydrogen peroxide or calcium hypochlorite).
- Ignoring the high pH and not handling with proper safety measures.
Uses of Sodium Hypochlorite in Real Life
Sodium hypochlorite has several important applications in everyday life and many industries:
- Major ingredient in household bleach for whitening and disinfecting laundry
- Disinfecting drinking water and swimming pools (water treatment)
- Cleaning surfaces and removing molds, stains, and odors
- Hospital use for antimicrobial surface cleaning
- Root canal disinfectant in dental procedures
- Wastewater treatment and industrial cleaning
Relation with Other Chemistry Concepts
Sodium hypochlorite is closely related to oxidation-reduction (redox) reactions because it acts as an oxidizing agent. It is also part of the acids, bases, and salts group in chemistry, helps explain the properties of salts, and connects with the study of bleaching agents like calcium hypochlorite and hydrogen peroxide.
Step-by-Step Reaction Example
1. Prepare cold, dilute sodium hydroxide solution in a beaker.2. Slowly bubble chlorine gas through the solution while stirring.
3. The reaction occurs as:
4. Sodium hypochlorite (NaOCl) forms in solution; table salt (NaCl) and water are also produced.
5. The solution can be used directly as bleach.
Lab or Experimental Tips
Remember to always work with sodium hypochlorite solutions in a well-ventilated area and store them in cool, dark bottles. Vedantu educators often use "never mix bleach with acids" as an easy-to-remember safety tip for students when handling this compound in labs.
Try This Yourself
- Write the IUPAC name and formula of sodium hypochlorite.
- Identify if sodium hypochlorite is acidic or basic in water.
- Give two real-life examples where sodium hypochlorite is used for disinfection.
Final Wrap-Up
We explored sodium hypochlorite—its structure, properties, reactions, and real-life importance. For more in-depth explanations, exam-prep tips, and interactive learning, check out live classes and notes on Vedantu or browse related chemistry topics for revision and practice.
FAQs on Sodium Hypochlorite in Chemistry: Formula, Properties & Uses
1. What is sodium hypochlorite?
Sodium hypochlorite is an inorganic chemical compound with the formula NaOCl that is widely used as a disinfectant and bleaching agent. It is most commonly recognized as the main active ingredient in household liquid bleach.
2. What is the chemical formula of sodium hypochlorite?
The chemical formula of sodium hypochlorite is NaOCl, which stands for sodium (Na), oxygen (O), and chlorine (Cl) combined in one ionic compound.
3. What are the main uses of sodium hypochlorite?
Sodium hypochlorite is used for:
- Disinfection and sanitation (e.g., surface and water treatment)
- Bleaching textiles or paper
- Odour removal
- Root canal treatment in dentistry
- Industrial cleaning
4. Is sodium hypochlorite the same as bleach?
Sodium hypochlorite is the primary ingredient in most household liquid bleach, but not all bleach products contain sodium hypochlorite. Always check the product label for specific ingredients.
5. What are the physical properties of sodium hypochlorite solution?
Sodium hypochlorite solution is typically:
- Pale greenish-yellow in color
- Strongly alkaline (pH 11–13)
- Highly soluble in water
- Has a characteristic, sharp chlorine-like odor
6. What happens when sodium hypochlorite is mixed with acid?
Mixing sodium hypochlorite with acid produces toxic chlorine gas, which is very dangerous. Always avoid combining bleach with acidic cleaners or substances.
7. What is the pH of a typical sodium hypochlorite solution?
Commercial sodium hypochlorite solutions usually have a pH between 11 and 13, making them strongly basic (alkaline).
8. Is hydrogen peroxide the same as sodium hypochlorite?
No, hydrogen peroxide (H2O2) and sodium hypochlorite (NaOCl) are different compounds. Both are oxidizing agents and disinfectants, but their chemical properties and applications differ.
9. Is sodium hypochlorite ionic or covalent?
Sodium hypochlorite is an ionic compound, composed of sodium cations (Na+) and hypochlorite anions (OCl-).
10. How is sodium hypochlorite prepared industrially?
Sodium hypochlorite is produced by:
- Bubbling chlorine gas through cold, dilute sodium hydroxide solution
- The reaction forms sodium hypochlorite, sodium chloride, and water
11. How does sodium hypochlorite act as a disinfectant?
Sodium hypochlorite kills bacteria and viruses by:
- Releasing active chlorine
- Oxidizing essential cell components
- Disrupting microbial cell membranes and enzymes
12. What safety precautions should be followed when using sodium hypochlorite?
When using sodium hypochlorite:
- Wear gloves and eye protection
- Avoid mixing with acids or ammonia
- Work in a well-ventilated area
- Store in a cool, dark place
- Follow label instructions and safety data sheets (SDS)
