Introduction: Chlorinated lime (bleaching powder, calcium hypochlorite) is a widely used antimicrobial disinfectant in pharmaceutical and public health settings. B.Pharm students must understand its chemistry, spectrum of activity, mechanism of action through free chlorine release, methods of preparation, stability issues, standardization, and safe handling. Key topics include appropriate concentrations for surface and water disinfection, effects of organic matter, neutralization, and limitations such as corrosiveness and inactivation. This concise overview links theory to practical pharmacy applications, quality control tests, and regulatory considerations to prepare students for exams and lab work. Study focus: pharmacopoeial standards, assay methods, and environmental safety. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. What is the primary active compound in chlorinated lime responsible for its antimicrobial action?
- Calcium chloride
- Calcium hydroxide
- Calcium hypochlorite (bleaching powder)
- Calcium carbonate
Correct Answer: Calcium hypochlorite (bleaching powder)
Q2. Which method is commonly used to determine the available chlorine content in chlorinated lime?
- Gravimetric sulfate method
- Iodometric titration
- pH titration with NaOH
- Colorimetric phenol method
Correct Answer: Iodometric titration
Q3. The antimicrobial activity of chlorinated lime is mainly due to the release of which species?
- Hydroxyl radicals
- Chlorine free radicals
- Free available chlorine (HOCl/OCl−)
- Hydrogen peroxide
Correct Answer: Free available chlorine (HOCl/OCl−)
Q4. Which of the following reduces the disinfectant efficacy of chlorinated lime in practical use?
- Low organic load
- Presence of organic matter
- Neutral pH
- Cold temperature
Correct Answer: Presence of organic matter
Q5. Which hazard arises when chlorinated lime reacts with acids?
- Formation of chlorine gas
- Production of ammonia gas
- Evolution of hydrogen
- Generation of ozone
Correct Answer: Formation of chlorine gas
Q6. Which titrant is used in the iodometric assay for available chlorine?
- 0.1 M NaOH
- 0.1 M Na2S2O3 (sodium thiosulfate)
- 0.1 M HCl
- 0.1 M KMnO4
Correct Answer: 0.1 M Na2S2O3 (sodium thiosulfate)
Q7. Bleaching powder is often described by an approximate formula. Which represents this conventional composition?
- Ca(OCl)2·CaCl2·Ca(OH)2
- CaCl2·2H2O
- CaO·H2O
- CaCO3·CaO
Correct Answer: Ca(OCl)2·CaCl2·Ca(OH)2
Q8. Which condition decreases the stability of chlorinated lime during storage?
- Dry, airtight container
- Exposure to moisture and CO2
- Storage in cool, dark place
- Packaging in moisture-proof bags
Correct Answer: Exposure to moisture and CO2
Q9. For water disinfection, what is the commonly referenced measure of chlorinated lime effectiveness?
- pH units neutralized
- Available chlorine (mg/L)
- Total dissolved solids
- Viscosity change
Correct Answer: Available chlorine (mg/L)
Q10. When chlorinated lime is added to water, the active disinfecting species formed at lower pH is:
- Hypochlorite ion (OCl−)
- Hypochlorous acid (HOCl)
- Chlorate ion (ClO3−)
- Chloride ion (Cl−)
Correct Answer: Hypochlorous acid (HOCl)
Q11. Which analytical indicator is used in the iodometric titration of available chlorine?
- Phenolphthalein
- Starch solution
- Methyl orange
- Turmeric indicator
Correct Answer: Starch solution
Q12. What is a major limitation of chlorinated lime as a disinfectant in organic-rich environments?
- Becomes more potent
- Gets rapidly inactivated
- Forms harmless by-products only
- Enhances microbial growth
Correct Answer: Gets rapidly inactivated
Q13. Which by-product classically forms when chlorinated lime reacts with nitrogenous organic matter?
- Carboxylic acids
- Nitrosamines and chloramines
- Simple alcohols
- Alkanes
Correct Answer: Nitrosamines and chloramines
Q14. The pharmacopoeial test to assess the available chlorine in bleaching powder typically requires liberation of iodine from which reagent?
- Potassium iodide
- Silver nitrate
- Potassium permanganate
- Ferric chloride
Correct Answer: Potassium iodide
Q15. Which chemical neutralizes residual chlorine from chlorinated lime before sewage discharge?
- Sodium hypochlorite
- Sodium thiosulfate
- Calcium carbonate
- Potassium permanganate
Correct Answer: Sodium thiosulfate
Q16. Which of the following is an advantage of chlorinated lime over gaseous chlorine for field disinfection?
- Higher volatility
- Safer solid transport and storage
- Produces stronger fumes
- Requires complex metering equipment
Correct Answer: Safer solid transport and storage
Q17. What is the likely effect of high temperatures on bleaching powder during storage?
- Enhanced shelf-life
- Accelerated decomposition and loss of available chlorine
- No effect on potency
- Converts to pure calcium chloride
Correct Answer: Accelerated decomposition and loss of available chlorine
Q18. In quality control, available chlorine is often expressed as percentage. A sample labeled 30% available chlorine refers to what?
- 30% by volume is chlorine gas
- 30 g of available chlorine per 100 g of sample
- 30 mg per liter in solution
- 30% humidity content
Correct Answer: 30 g of available chlorine per 100 g of sample
Q19. Which of the following microbes is least susceptible to chlorinated lime at typical disinfectant concentrations?
- Vegetative bacteria
- Enveloped viruses
- Protozoan cysts (e.g., Cryptosporidium)
- Fungi
Correct Answer: Protozoan cysts (e.g., Cryptosporidium)
Q20. Which safety precaution is essential when handling chlorinated lime powder in the laboratory?
- Work in a closed, unventilated room
- Use personal protective equipment and avoid inhalation
- Mix with acids to test activity
- Store near combustible materials
Correct Answer: Use personal protective equipment and avoid inhalation
Q21. Which reagent is used to neutralize residual hypochlorite in disinfected surfaces before conducting microbial culture sampling?
- Sodium chloride
- Sodium thiosulfate solution
- Sulfuric acid
Correct Answer: Sodium thiosulfate solution
Q22. The reaction of chlorinated lime with excess iodide under acidic conditions liberates iodine. The iodine is then titrated with thiosulfate. What is the role of acid in this procedure?
- Neutralizes thiosulfate
- Converts hypochlorite to chlorine which oxidizes iodide to iodine
- Precipitates calcium salts
- Reduces iodine to iodide
Correct Answer: Converts hypochlorite to chlorine which oxidizes iodide to iodine
Q23. Which formulation characteristic of chlorinated lime determines its dustiness and handling safety?
- Particle size and granulation
- Color only
- pH of a saturated solution
- Available chlorine solely
Correct Answer: Particle size and granulation
Q24. Which compound is produced when chlorinated lime decomposes in moist air over time?
- Chlorine gas exclusively
- Calcium chloride and loss of available chlorine
- Elemental calcium
- Sodium chloride
Correct Answer: Calcium chloride and loss of available chlorine
Q25. In disinfection protocols, why is contact time important when using chlorinated lime?
- Shorter contact time always increases efficacy
- Microbial inactivation depends on both concentration and time
- Contact time only matters for heat sterilization
- Chlorinated lime acts instantaneously regardless of time
Correct Answer: Microbial inactivation depends on both concentration and time
Q26. Which parameter must be controlled when preparing a working solution of chlorinated lime for surface disinfection?
- The ionic strength of sodium chloride
- Available chlorine concentration and pH
- The concentration of ethanol
- Amount of sugar present
Correct Answer: Available chlorine concentration and pH
Q27. Mixing chlorinated lime with which household chemical can produce toxic chloramine gases?
- Vinegar (acetic acid)
- Ammonia-containing cleaners
- Isopropyl alcohol
- Baking soda
Correct Answer: Ammonia-containing cleaners
Q28. Chlorinated lime is included in the pharmacopeial monograph primarily as which type of agent?
- Antiseptic for internal use
- Topical anesthetic
- Disinfectant and bleaching agent
- Systemic antibiotic
Correct Answer: Disinfectant and bleaching agent
Q29. Which storage condition minimizes loss of available chlorine in bleaching powder?
- Open sack in humid area
- Sealed container in dry, cool place
- Exposure to sunlight
- Near acids for quick access
Correct Answer: Sealed container in dry, cool place
Q30. Which test checks for excess free alkali in bleaching powder samples?
- Acid-base titration with HCl
- Measurement of refractive index
- Colorimetric nitrate test
- Viscosity determination
Correct Answer: Acid-base titration with HCl
Q31. In a standard assay, why is potassium iodide added before acidification when determining available chlorine?
- To solubilize calcium salts
- To reduce iodine to iodide
- To provide iodide ions that are oxidized to iodine
- To neutralize alkalinity
Correct Answer: To provide iodide ions that are oxidized to iodine
Q32. The term “available chlorine” quantifies which aspect of a chlorinated disinfectant?
- Total calcium content
- Oxidizing capacity expressed as chlorine equivalent
- pH buffering capacity
- Amount of residual odor
Correct Answer: Oxidizing capacity expressed as chlorine equivalent
Q33. Which pharmacopoeia commonly provides standards and assays for bleaching powder used in pharmaceutical settings?
- European Pharmacopoeia and Pharmacopoeia of India
- Codex Alimentarius only
- USP exclusively for surfactants
- ASTM for metals
Correct Answer: European Pharmacopoeia and Pharmacopoeia of India
Q34. Bleaching powder may slowly lose strength due to reaction with atmospheric carbon dioxide forming which product?
- Calcium carbonate
- Calcium peroxide
- Sodium carbonate
- Calcium sulfate
Correct Answer: Calcium carbonate
Q35. Which monitoring practice is essential when using chlorinated lime for hospital surface disinfection?
- Ignoring contact time
- Periodic testing of working solution for available chlorine
- Using solutions prepared months earlier
- Mixing with quaternary ammonium compounds freely
Correct Answer: Periodic testing of working solution for available chlorine
Q36. Which of the following is an environmental concern with extensive use of chlorinated lime?
- Biodegradable residues only
- Formation of toxic chlorinated organic by-products in effluents
- Exclusive formation of harmless salts
- Neutral pH of discharged water
Correct Answer: Formation of toxic chlorinated organic by-products in effluents
Q37. During assay, excess iodine liberated is titrated until the blue starch color disappears. What does disappearance of the blue color indicate?
- All iodine converted to iodide
- Presence of excess chlorine
- No reaction occurred
- Solution became alkaline
Correct Answer: All iodine converted to iodide
Q38. Which of the following best describes the mechanism by which hypochlorous acid inactivates microbes?
- Interferes with membrane lipids and oxidizes sulfhydryl groups in enzymes
- Acts as a nutrient to microbes
- Forms physical barrier around cells
- Increases osmotic pressure to lyse cells
Correct Answer: Interferes with membrane lipids and oxidizes sulfhydryl groups in enzymes
Q39. Which concentration unit is typically used when preparing working disinfectant solutions from chlorinated lime for cleaning?
- Percentage by weight for solid only
- mg/L (ppm) of available chlorine
- Molality in moles/kg
- Viscosity units
Correct Answer: mg/L (ppm) of available chlorine
Q40. What is the expected pH range of an aqueous solution of chlorinated lime?
- Strongly acidic (pH 1–3)
- Neutral (pH 7)
- Alkaline (pH around 10–12)
- Variable but always below 4
Correct Answer: Alkaline (pH around 10–12)
Q41. Which pharmaceutical application might use chlorinated lime as an excipient or processing aid?
- As an active systemic drug
- For disinfection of equipment and surfaces in production areas
- In tablet flavoring
- As a binder in capsules
Correct Answer: For disinfection of equipment and surfaces in production areas
Q42. If a chlorinated lime sample shows lower available chlorine than label claim, which quality control step is appropriate?
- Use higher volumes regardless of assay
- Reject or restandardize the batch and report stability issue
- Ignore if color appears normal
- Mix with acid to restore chlorine
Correct Answer: Reject or restandardize the batch and report stability issue
Q43. When preparing a disinfectant solution from bleaching powder, why should freshly prepared solutions be preferred?
- Because available chlorine in solution remains constant for months
- Available chlorine decays over time, reducing efficacy
- Old solutions become stronger
- Fresh solutions are cheaper
Correct Answer: Available chlorine decays over time, reducing efficacy
Q44. Which of the following analytical interferences can lead to overestimation of available chlorine in iodometric titration?
- Presence of reducing agents in sample
- Presence of other oxidizing agents that also oxidize iodide
- Poor diffusion of oxygen
- Low temperature only
Correct Answer: Presence of other oxidizing agents that also oxidize iodide
Q45. Which personal protective equipment (PPE) is most important when preparing hypochlorite solutions from bleaching powder?
- Light clothing only
- Gloves, goggles, and apron
- No PPE needed for dilute solutions
- Ear protection
Correct Answer: Gloves, goggles, and apron
Q46. Which statement correctly compares sodium hypochlorite solution to chlorinated lime?
- Sodium hypochlorite is a solid; chlorinated lime is liquid
- Both release available chlorine, but sodium hypochlorite is stored as solution while chlorinated lime is a more stable solid
- Chlorinated lime has no oxidizing ability
- Sodium hypochlorite cannot be used for water disinfection
Correct Answer: Both release available chlorine, but sodium hypochlorite is stored as solution while chlorinated lime is a more stable solid
Q47. In an industrial spill of chlorinated lime powder, what is the priority action?
- Cover with acids to neutralize
- Prevent contact with moisture and evacuate the area if dust or fumes present
- Ignite to burn material safely
- Flush with large amounts of water immediately in confined area
Correct Answer: Prevent contact with moisture and evacuate the area if dust or fumes present
Q48. What analytical calculation converts titration result (mL Na2S2O3 used) into percentage available chlorine?
- Use stoichiometry: moles thiosulfate → moles iodine → moles equivalent chlorine → mass chlorine per sample mass
- Multiply titrant volume by pH
- Divide titrant volume by sample odour intensity
- Use refractive index chart
Correct Answer: Use stoichiometry: moles thiosulfate → moles iodine → moles equivalent chlorine → mass chlorine per sample mass
Q49. Which monitoring parameter is critical when chlorinated lime is used for potable water treatment?
- Residual chlorine concentration and consumer safety limits
- Color of container
- Amount of calcium carbonate only
- Temperature of storage room only
Correct Answer: Residual chlorine concentration and consumer safety limits
Q50. For exam-oriented practical knowledge, which concept about chlorinated lime is essential for B.Pharm students to master?
- Only its color and odor
- Chemistry of available chlorine, assay methods, factors affecting stability and safe handling
- How to synthesize it from sodium chloride at home
- Its role as an oral medication
Correct Answer: Chemistry of available chlorine, assay methods, factors affecting stability and safe handling
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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