Basic Chemical Information
| Aspect | Formula/Information | Explanation |
|---|---|---|
| Chemical Formula | Ca(OCl)₂ | Most commonly accepted molecular formula for bleaching powder |
| Alternative Formula | CaOCl₂ | Alternative way to represent the same compound |
| Empirical Formula | Ca(OCl)₂ | Simplest whole number ratio of atoms |
| IUPAC Name | Calcium hypochlorite | Official chemical name as per IUPAC nomenclature |
| Common Names | Bleaching powder, Chlorinated lime, Calcium oxychloride | Various names used in industry and education |
| Molecular Weight | 142.98 g/mol | Molar mass calculated from atomic weights |
Preparation Formulas
| Method | Chemical Equation | Explanation |
|---|---|---|
| Laboratory Method | Ca(OH)₂ + Cl₂ → Ca(OCl)₂ + H₂O | Slaked lime reacts with chlorine gas |
| Industrial Method | Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O | Large-scale production using lime and chlorine |
| Balanced Equation | Ca(OH)₂ + Cl₂ → Ca(OCl)₂ + H₂O | Complete balanced chemical equation |
Decomposition Formulas
| Type of Decomposition | Chemical Equation | Conditions |
|---|---|---|
| Thermal Decomposition | 3Ca(OCl)₂ → Ca(ClO₃)₂ + 2CaCl₂ | Heat applied |
| Acid Decomposition | Ca(OCl)₂ + 2HCl → CaCl₂ + Cl₂ + H₂O | With hydrochloric acid |
| CO₂ Decomposition | Ca(OCl)₂ + CO₂ → CaCO₃ + Cl₂O | Exposure to carbon dioxide |
| Water Decomposition | Ca(OCl)₂ + H₂O → Ca(OH)₂ + Cl₂O | In presence of water |
Bleaching Mechanism Formulas
| Process | Chemical Equation | Mechanism |
|---|---|---|
| Oxidation Process | Ca(OCl)₂ + H₂O → Ca(OH)₂ + Cl₂O | First step in bleaching |
| Active Chlorine Release | Cl₂O + H₂O → 2HClO | Formation of hypochlorous acid |
| Bleaching Action | Organic Matter + [O] → Oxidized Product | Oxygen from HClO bleaches organic materials |
| Complete Process | Colored Substance + HClO → Colorless Substance + HCl | Overall bleaching reaction |
Related Compounds and Formulas
| Compound Name | Chemical Formula | Relationship to Bleaching Powder |
|---|---|---|
| Calcium Hydroxide | Ca(OH)₂ | Starting material (slaked lime) |
| Chlorine Gas | Cl₂ | Starting material for preparation |
| Calcium Chloride | CaCl₂ | Byproduct in some reactions |
| Hypochlorous Acid | HClO | Active bleaching agent formed |
| Calcium Chlorate | Ca(ClO₃)₂ | Product of thermal decomposition |
| Chlorine Monoxide | Cl₂O | Intermediate compound in bleaching |
Important Calculations and Formulas
| Calculation Type | Formula | Application |
|---|---|---|
| Available Chlorine | % Available Cl₂ = (35.5/71) × 100 = 50% | Quality determination of bleaching powder |
| Equivalent Weight | Equivalent Weight = Molecular Weight/2 = 71.49 | For stoichiometric calculations |
| Concentration Formula | Molarity = (Weight in g)/(Molecular Weight × Volume in L) | For solution preparation |
| Bleaching Capacity | 1 mole Ca(OCl)₂ = 1 mole available Cl₂ | Theoretical bleaching capacity |
Physical and Chemical Properties
| Property | Value/Description | Significance |
|---|---|---|
| Physical State | White powder | Easy identification |
| Solubility | Partially soluble in water | Forms calcium hypochlorite solution |
| Odor | Strong chlorine smell | Indicates active chlorine content |
| pH of Solution | Basic (pH > 7) | Due to Ca(OH)₂ formation |
| Stability | Unstable in air and light | Requires proper storage |
| Melting Point | Decomposes before melting | Thermal instability |
Safety and Storage Information
| Aspect | Details | Chemical Basis |
|---|---|---|
| Storage Requirements | Cool, dry, dark place | Prevents decomposition: Ca(OCl)₂ → products |
| Incompatible Substances | Acids, organic materials | Forms toxic chlorine gas: Ca(OCl)₂ + acid → Cl₂ |
| Safety Precautions | Avoid contact with skin/eyes | HClO formation can cause burns |
| First Aid | Flush with water immediately | Neutralizes hypochlorous acid |
Points for Students
- Remember the Formula: Ca(OCl)₂ is the most important formula to memorize
- Preparation: Always involves Ca(OH)₂ + Cl₂ reaction
- Bleaching Mechanism: Works by releasing active oxygen [O]
- Storage: Must be kept away from acids and moisture
- Uses: Water disinfection, textile bleaching, and sanitization
Practice Questions Format
| Question Type | Example | Answer Format |
|---|---|---|
| Formula Writing | Write the chemical formula of bleaching powder | Ca(OCl)₂ |
| Equation Balancing | Balance: Ca(OH)₂ + Cl₂ → ? | Ca(OH)₂ + Cl₂ → Ca(OCl)₂ + H₂O |
| Name to Formula | Give formula for calcium hypochlorite | Ca(OCl)₂ |
| Calculation | Calculate molecular weight | 40 + 16 + 2(35.5) = 142.98 g/mol |
Note for Students: This comprehensive guide covers all essential formulas related to bleaching powder. Focus on memorizing the basic formula Ca(OCl)₂ and understanding the preparation method. Practice writing balanced equations and calculating molecular weights for better exam preparation.
Frequently Asked Questions (FAQs)
Q. What is the chemical formula of bleaching powder?
The chemical formula of bleaching powder is Ca(OCl)₂ or CaOCl₂. Its IUPAC name is calcium hypochlorite. The molecular weight is 142.98 g/mol. Bleaching powder contains calcium, oxygen, and chlorine atoms in the ratio of 1:1:2. It is also known as chlorinated lime or calcium oxychloride and appears as a white powder with a strong chlorine smell.
Q. How is bleaching powder prepared? Write the chemical equation.
Bleaching powder is prepared by passing chlorine gas over dry slaked lime (calcium hydroxide). The chemical equation is:
Ca(OH)₂ + Cl₂ → Ca(OCl)₂ + H₂O
In this reaction, calcium hydroxide reacts with chlorine gas to produce calcium hypochlorite (bleaching powder) and water. This method is used both in laboratories and industries. The reaction requires dry slaked lime because moisture can cause side reactions.
Q. What happens when bleaching powder reacts with dilute acids?
When bleaching powder reacts with dilute acids like hydrochloric acid (HCl), it produces chlorine gas. The chemical equation is:
Ca(OCl)₂ + 2HCl → CaCl₂ + Cl₂↑ + H₂O
This reaction releases toxic chlorine gas (Cl₂), which has a pungent smell. This is why bleaching powder should never be stored near acids. The products formed are calcium chloride, chlorine gas, and water. This property is used in laboratories to prepare chlorine gas.
Q. What is the difference between bleaching powder and chlorine?
| Aspect | Bleaching Powder | Chlorine |
|---|---|---|
| Formula | Ca(OCl)₂ | Cl₂ |
| State | White solid powder | Greenish-yellow gas |
| Stability | More stable, easier to store | Highly reactive, difficult to store |
| Bleaching Action | Releases chlorine slowly | Direct bleaching agent |
| Uses | Water treatment, disinfection | Industrial bleaching, water purification |
| Safety | Safer to handle | Toxic and corrosive |
Bleaching powder is a solid compound containing chlorine, while chlorine is a gaseous element. Bleaching powder is preferred in households because it’s safer and easier to handle than pure chlorine gas.
Q. How does bleaching powder work as a bleaching agent?
Bleaching powder works by releasing active oxygen [O] which oxidizes colored substances to colorless compounds. The mechanism involves:
Step 1: Ca(OCl)₂ + H₂O → Ca(OH)₂ + Cl₂O
Step 2: Cl₂O + H₂O → 2HClO (Hypochlorous acid)
Step 3: HClO → HCl + [O] (Active oxygen)
Step 4: Colored Substance + [O] → Colorless Oxidized Product
The hypochlorous acid (HClO) is the actual bleaching agent that provides nascent oxygen. This oxygen oxidizes the chromophores (color-causing groups) in organic materials, making them colorless. This is why bleaching powder is effective for removing stains and disinfecting surfaces.
Q. What is the percentage of available chlorine in bleaching powder?
Good quality bleaching powder contains approximately 35-40% available chlorine. The theoretical maximum is 50%, but commercial bleaching powder typically contains 35-38% due to impurities and partial decomposition during storage.
Calculation:
- Molecular weight of Ca(OCl)₂ = 142.98 g/mol
- Available chlorine = 71 g/mol (equivalent to one Cl₂ molecule)
- Percentage = (71/142.98) × 100 = 49.65% ≈ 50% (theoretical)
The available chlorine content indicates the bleaching power. Higher percentage means stronger bleaching action. This is tested using standard iodometric titration methods. Always check the available chlorine percentage when purchasing bleaching powder for best results.