Bromatometry – principles and applications MCQs With Answer

Bromatometry – principles and applications MCQs With Answer

Bromatometry is a redox titration technique widely used in pharmaceutical analysis where bromine, usually generated in situ from potassium bromate and bromide in acidic medium, acts as the oxidant. B. Pharm students should master core principles: generation of Br2 (BrO3- + 5Br- + 6H+ → 3Br2 + 3H2O), choice of non‑oxidizing acid, indicator selection (starch/iodometric back titration), standardization and interference control. Applications include assay of ascorbic acid and other reducible drugs, quality control and stability testing. Practical aspects cover safety, stoichiometry, end‑point detection and calculation methods. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is bromatometry?

• A titration method using bromine/bromate as oxidant in redox analysis
• A chromatographic separation technique for brominated compounds
• A spectrophotometric method for measuring bromide concentration
• A microbial test for bromide contamination

Correct Answer: A titration method using bromine/bromate as oxidant in redox analysis

Q2. Which reagent pair is commonly used to generate bromine in situ for bromatometric titrations?

• Potassium bromate and potassium bromide in acidic medium
• Potassium permanganate and sodium chloride
• Potassium iodate and sodium iodide
• Sodium hypochlorite and sodium bromide

Correct Answer: Potassium bromate and potassium bromide in acidic medium

Q3. What is the balanced reaction for bromine generation from bromate and bromide in acid?

• BrO3- + 5Br- + 6H+ → 3Br2 + 3H2O
• BrO3- + Br- + 2H+ → Br2 + H2O
• BrO3- + 3Br- + 3H+ → 2Br2 + 3H2O
• BrO3- + 2Br- + 4H+ → 2Br2 + 2H2O

Correct Answer: BrO3- + 5Br- + 6H+ → 3Br2 + 3H2O

Q4. What is the oxidation state of bromine in bromate ion (BrO3-)?

• +5
• -1
• 0
• +3

Correct Answer: +5

Q5. Which medium is essential for efficient in situ generation of bromine during bromatometric titrations?

• Strong acidic medium (e.g., sulfuric acid)
• Strong basic medium (e.g., sodium hydroxide)
• Neutral buffer (pH 7)
• Organic solvent (e.g., ethanol)

Correct Answer: Strong acidic medium (e.g., sulfuric acid)

Q6. Why is sulfuric acid preferred over hydrochloric acid in many bromatometric procedures?

• Because chloride from HCl can be oxidized, causing interference
• Because sulfuric acid produces a vivid endpoint color
• Because HCl reacts with bromate to form hypobromous acid
• Because HCl is not strong enough to generate bromine

Correct Answer: Because chloride from HCl can be oxidized, causing interference

Q7. Which indicator strategy is commonly used to detect the end point in bromatometry by back titration?

• Convert residual bromine to iodine with KI and detect iodine with starch
• Use phenolphthalein as a redox indicator
• Measure pH change with methyl orange
• Use Nessler’s reagent to detect bromide

Correct Answer: Convert residual bromine to iodine with KI and detect iodine with starch

Q8. Which pharmaceutical analyte is frequently determined by bromatometric methods?

• Ascorbic acid (vitamin C)
• Paracetamol (acetaminophen)
• Ibuprofen
• Metformin

Correct Answer: Ascorbic acid (vitamin C)

Q9. What is a principal advantage of bromatometry compared to iodometry?

• Bromine has a stronger oxidizing power and can oxidize substrates not affected by iodine
• Bromatometry is always faster than iodometry
• Bromatometry does not require acidic medium
• Bromatometry produces no toxic vapors

Correct Answer: Bromine has a stronger oxidizing power and can oxidize substrates not affected by iodine

Q10. What type of titration is bromatometry classified as?

• Redox titration
• Complexometric titration
• Acid-base titration
• Precipitation titration

Correct Answer: Redox titration

Q11. Which ion can cause significant interference in bromatometric determinations by being preferentially oxidized?

• Iodide (I-)
• Sodium (Na+)
• Calcium (Ca2+)
• Magnesium (Mg2+)

Correct Answer: Iodide (I-)

Q12. In the stoichiometry of bromine generation, how many moles of bromide are consumed per mole of bromate?

• 5 moles of bromide per mole of bromate
• 1 mole of bromide per mole of bromate
• 3 moles of bromide per mole of bromate
• 2 moles of bromide per mole of bromate

Correct Answer: 5 moles of bromide per mole of bromate

Q13. If 20.0 mL of 0.020 M potassium bromate is used and fully converts to bromine, how many millimoles of Br2 are produced? (1 mol BrO3- → 3 mol Br2)

• 1.20 mmol
• 0.40 mmol
• 3.00 mmol
• 6.00 mmol

Correct Answer: 1.20 mmol

Q14. Which practical safety precaution is essential when performing bromatometric titrations?

• Work in a fume hood and use acid-resistant gloves due to toxic bromine vapors
• Always heat the sample to drive off bromine
• Use open flames to disperse bromine vapors
• Store bromate solutions near organic solvents

Correct Answer: Work in a fume hood and use acid-resistant gloves due to toxic bromine vapors

Q15. What is a common instrumental method used to detect the end point or monitor bromination reactions more precisely?

• Spectrophotometry (measuring absorbance of bromine or iodine complexes)
• Gas chromatography of bromine vapors
• Mass spectrometry of bromide ion
• Infrared spectroscopy of bromide

Correct Answer: Spectrophotometry (measuring absorbance of bromine or iodine complexes)

Q16. Which mechanism best describes electrophilic bromination of activated aromatic rings occurring during some bromatometric assays?

• Electrophilic aromatic substitution
• Nucleophilic aliphatic substitution
• Free radical halogenation
• SN1 reaction

Correct Answer: Electrophilic aromatic substitution

Q17. Which of the following is a disadvantage of bromatometry?

• Toxic and volatile nature of bromine requires strict safety control
• It cannot oxidize strong reducing agents
• End points are always ambiguous and cannot be detected
• It is unaffected by acidity changes

Correct Answer: Toxic and volatile nature of bromine requires strict safety control

Q18. What is the role of potassium bromate in bromatometry?

• Primary oxidizing agent (source of BrO3- to generate Br2)
• Primary reducing agent
• Complexing agent for metal ions
• Acidifying agent to set pH

Correct Answer: Primary oxidizing agent (source of BrO3- to generate Br2)

Q19. Why is an iodometric back titration often preferred after bromination?

• Residual bromine can be quantitatively converted to iodine, and iodine gives a sharp starch endpoint
• Iodometric back titration neutralizes acids without indicators
• Because iodometry uses non-aqueous solvents exclusively
• Because iodine is a weaker oxidant so it won’t react further

Correct Answer: Residual bromine can be quantitatively converted to iodine, and iodine gives a sharp starch endpoint

Q20. Which of these substances is most suitable for standardizing a bromate solution in practice?

• A primary standard that can be accurately weighed, such as sodium oxalate (via indirect iodometric routes)
• Organic dye that reacts slowly with bromine
• Hydrochloric acid directly
• Pure water

Correct Answer: A primary standard that can be accurately weighed, such as sodium oxalate (via indirect iodometric routes)

Q21. Which ion, if present in sample, is least likely to be oxidized by bromine under typical conditions?

• Sodium ion (Na+)
• Sulfite ion (SO3 2-)
• Ferrous ion (Fe2+)
• Hydrogen sulfide (H2S)

Correct Answer: Sodium ion (Na+)

Q22. What endpoint color change is expected when iodine is titrated with sodium thiosulfate using starch indicator?

• Blue (iodine-starch) to colorless
• Red to yellow
• Orange to pink
• Green to blue

Correct Answer: Blue (iodine-starch) to colorless

Q23. Which factor most strongly affects the rate of bromination reactions in bromatometric assays?

• Acidity (proton concentration)
• Ambient light intensity
• Magnetic field strength
• Atmospheric pressure

Correct Answer: Acidity (proton concentration)

Q24. In pharmaceutical quality control, bromatometry is especially useful for determining which functional property of a drug substance?

• Reducing capacity or content of oxidizable groups
• Melting point
• Optical rotation
• Lipid solubility

Correct Answer: Reducing capacity or content of oxidizable groups

Q25. What storage precaution is important for solid potassium bromate?

• Store in a cool, dry place away from organics and reducing agents
• Keep next to flammable solvents for stability
• Store in direct sunlight to maintain potency
• Keep mixed with powdered charcoal to prevent decomposition

Correct Answer: Store in a cool, dry place away from organics and reducing agents

Q26. In direct bromatometric titration, what is monitored to determine the end point when possible?

• Disappearance of bromine’s brown/yellow color or conversion measured spectrophotometrically
• Increase of pH to neutral
• Formation of a precipitate
• Evolution of a gas

Correct Answer: Disappearance of bromine’s brown/yellow color or conversion measured spectrophotometrically

Q27. Which of the following best describes why bromatometry requires careful control of sample matrix?

• Other oxidizable or reducible species and halides can consume bromine and cause errors
• Matrix components evaporate bromine
• Sample matrix always neutralizes acid
• Matrix components change potassium bromate into permanganate

Correct Answer: Other oxidizable or reducible species and halides can consume bromine and cause errors

Q28. Which analytical advantage does converting bromine to iodine and titrating with thiosulfate provide?

• A sharper, more reproducible visual endpoint via the iodine-starch reaction
• It eliminates need for acid
• It reduces the number of reaction steps
• It avoids the use of any oxidizing agents

Correct Answer: A sharper, more reproducible visual endpoint via the iodine-starch reaction

Q29. Which of the following is an appropriate environmental or waste consideration for bromatometry labs?

• Neutralize and reduce bromine/bromate residues before disposal and follow local hazardous-waste rules
• Pour all waste down the sink since bromine is non-toxic
• Burn bromate salts in open air to decompose them
• Mix bromate waste with organic solvents to enhance dilution

Correct Answer: Neutralize and reduce bromine/bromate residues before disposal and follow local hazardous-waste rules

Q30. Which statement about bromatometry’s role in pharmaceutical analysis is most accurate?

• It is a valuable redox titration method for assaying oxidizable drug components when properly standardized and controlled
• It has been entirely replaced by chromatographic methods and has no practical use
• It is only useful for inorganic salt assays and not for organic drugs
• It requires no reagents and is performed directly on tablets without preparation

Correct Answer: It is a valuable redox titration method for assaying oxidizable drug components when properly standardized and controlled

G S Sachin

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.

Mail- Sachin@pharmacyfreak.com