Sodium hypochlorite (NaOCl) is a chemical compound that is commonly used as a disinfectant, bleaching agent, and in water treatment processes. It is most well-known as the active ingredient in household bleach and industrial disinfectants.
Properties:
- Chemical formula: NaOCl
- Molar mass: 74.44 g/mol
- Appearance: Usually found as a pale greenish-yellow liquid (in aqueous solutions)
- Odor: Characteristic chlorine-like smell
- Solubility: Highly soluble in water
- pH: Sodium hypochlorite solutions are strongly alkaline, typically with a pH around 11-13
Production:
Sodium hypochlorite is typically produced by bubbling chlorine gas through a cold, dilute sodium hydroxide (caustic soda) solution:
Cl₂+2NaOH→NaCl+NaOCl+H₂O\text{Cl₂} + 2\text{NaOH} → \text{NaCl} + \text{NaOCl} + \text{H₂O}Cl₂+2NaOH→NaCl+NaOCl+H₂O
Common Uses:
1. Disinfectant:
Sodium hypochlorite is widely used as a disinfectant because of its ability to kill bacteria, viruses, fungi, and algae:
- Household bleach: In low concentrations (typically 3-8%), sodium hypochlorite is the active ingredient in bleach products used for disinfecting surfaces, laundry, and household cleaning.
- Healthcare and sanitation: It is used in hospitals and clinics for sterilizing medical equipment, cleaning surfaces, and disinfecting contaminated areas.
- Water treatment: Sodium hypochlorite is commonly used in the disinfection of drinking water and wastewater. It eliminates pathogens and makes water safe for consumption or release into the environment.
2. Bleaching Agent:
Sodium hypochlorite is a powerful bleaching agent:
- Textiles: It is used in the textile industry to bleach fabrics, especially cotton and other natural fibers.
- Paper industry: It is used to bleach wood pulp in the production of white paper products.
3. Water Treatment:
Sodium hypochlorite plays a vital role in water treatment processes:
- Municipal water treatment: It is added to water supplies to kill harmful microorganisms and ensure the water is safe for public consumption. This is an alternative to chlorine gas, offering a safer handling method.
- Wastewater treatment: Sodium hypochlorite is used in wastewater treatment plants to disinfect and reduce odors before the water is released back into the environment.
4. Industrial Cleaning:
In industrial applications, sodium hypochlorite is used as a cleaning agent:
- Food processing: It is used to sanitize equipment and surfaces in food and beverage production facilities.
- Petroleum industry: Sodium hypochlorite can be used to clean and disinfect pipelines and storage tanks.
5. Chlorination of Pools:
It is commonly used for the chlorination of swimming pools:
- Algae and bacteria control: Sodium hypochlorite is used to maintain the cleanliness of pool water by killing algae, bacteria, and viruses. It is usually added at low concentrations and continuously monitored to maintain water quality.
6. Odor Removal:
Sodium hypochlorite is effective at removing odors by breaking down foul-smelling organic compounds. It is often used in garbage disposal units, drains, and areas with persistent bad odors.
Chemical Reactions:
- Disinfection: The active ingredient in sodium hypochlorite solutions is hypochlorous acid (HOCl), which forms when sodium hypochlorite is dissolved in water. Hypochlorous acid is a powerful oxidizer that destroys microorganisms by breaking down their cell walls and interfering with their metabolic functions. NaOCl+H₂O⇌HOCl+NaOH\text{NaOCl} + \text{H₂O} ⇌ \text{HOCl} + \text{NaOH}NaOCl+H₂O⇌HOCl+NaOH
- Decomposition: Sodium hypochlorite is not stable and can decompose over time, especially when exposed to light, heat, or acidic conditions. This is why bleach solutions must be stored in cool, dark places and should not be mixed with acids or other cleaners. 3NaOCl→2NaCl+NaClO₃3\text{NaOCl} → 2\text{NaCl} + \text{NaClO₃}3NaOCl→2NaCl+NaClO₃ When mixed with acids, sodium hypochlorite releases chlorine gas (Cl₂), which is highly toxic.
Sodium hypochlorite’s versatility in disinfection, bleaching, and water treatment makes it one of the most widely used chemicals in household and industrial applications
