Applications of buffers MCQs With Answer

Introduction: Applications of buffers MCQs With Answer is an essential resource for B.Pharm students preparing for exams and practicals. This concise guide explores buffer systems, pH control, Henderson-Hasselbalch calculations, buffer capacity, and real-world pharmaceutical applications such as formulation stability, parenterals, ophthalmic solutions, protein drug stabilization, and dissolution testing. Each question reinforces core concepts like buffer selection, ionic strength, common‑ion effects, sterilization impacts, and how pH influences drug ionization and solubility. Practicing these MCQs will strengthen problem-solving and decision-making skills required in formulation development and quality control. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the primary function of a buffer in pharmaceutical formulations?

• To act as an active drug substance
• To resist changes in pH when small amounts of acid or base are added
• To increase the viscosity of the formulation
• To serve as a preservative

Correct Answer: To resist changes in pH when small amounts of acid or base are added

Q2. Which two components make up a typical buffer system?

• A strong acid and a strong base
• An acid and its conjugate base or a base and its conjugate acid
• Two neutral salts
• A solvent and a surfactant

Correct Answer: An acid and its conjugate base or a base and its conjugate acid

Q3. The Henderson-Hasselbalch equation is primarily used to:

• Calculate osmolality
• Estimate the pH of a buffer from pKa and ratio of conjugate base to acid
• Determine drug partition coefficients
• Predict steric hindrance in molecules

Correct Answer: Estimate the pH of a buffer from pKa and ratio of conjugate base to acid

Q4. For effective buffering, the useful pH range of a buffer is approximately:

• pKa ± 3 units
• pKa ± 2 units
• pKa ± 1 unit
• pKa only

Correct Answer: pKa ± 1 unit

Q5. Buffer capacity is highest when:

• The concentration of acid is much greater than the base
• The concentration of base is much greater than the acid
• The concentrations of the weak acid and its conjugate base are equal
• The buffer is highly diluted

Correct Answer: The concentrations of the weak acid and its conjugate base are equal

Q6. How does dilution affect buffer capacity?

• Dilution increases buffer capacity
• Dilution has no effect on buffer capacity
• Dilution decreases buffer capacity
• Dilution converts buffer into a neutral solution

Correct Answer: Dilution decreases buffer capacity

Q7. Which buffer is most appropriate for maintaining physiological pH (~7.4) in many pharmaceutical formulations?

• Acetate buffer
• Phosphate buffer
• Citrate buffer
• Borate buffer

Correct Answer: Phosphate buffer

Q8. The common ion effect in buffers refers to:

• The generation of free radicals by buffers
• Precipitation of buffer salts
• Suppression of ionization of a weak acid or base by adding a common ion
• Increase in buffer viscosity

Correct Answer: Suppression of ionization of a weak acid or base by adding a common ion

Q9. Using Henderson-Hasselbalch, what is the pH when pKa = 4.76 and [A-]/[HA] = 1?

• 3.76
• 4.76
• 5.76
• 6.76

Correct Answer: 4.76

Q10. If acetic acid (pKa 4.76) buffer has [A-]/[HA] = 0.1, what is the approximate pH?

• 5.76
• 4.76
• 3.76
• 2.76

Correct Answer: 3.76

Q11. Which buffer is commonly used for solutions requiring pH around 4 to 6, such as some oral or topical products?

• Acetate buffer
• Phosphate buffer
• Borate buffer
• Ammonium buffer

Correct Answer: Acetate buffer

Q12. Which buffer component can chelate divalent metal ions and potentially affect formulation stability?

• Sodium chloride
• Citrate
• Sucrose
• Polysorbate

Correct Answer: Citrate

Q13. At the half-equivalence point during titration of a weak acid with strong base, the pH equals:

• Zero
• Half of the pKa
• The pKa of the acid
• The pKb of the conjugate base

Correct Answer: The pKa of the acid

Q14. Which buffer is preferred for many protein and vaccine formulations due to favorable stabilization properties around neutral pH?

• Glycine buffer at pH 2
• Histidine buffer near pH 6–7
• Acetate buffer at pH 4
• Bicarbonate buffer at pH 10

Correct Answer: Histidine buffer near pH 6–7

Q15. Which buffer system is volatile and therefore often used when downstream evaporation or mass spectrometry compatibility is required?

• Phosphate buffer
• Ammonium acetate buffer
• Borate buffer
• Citrate buffer

Correct Answer: Ammonium acetate buffer

Q16. Why must buffer ionic strength be considered in formulation development?

• Ionic strength only affects color
• Ionic strength influences drug solubility, protein stability, and electrostatic interactions
• Ionic strength eliminates preservatives
• Ionic strength is irrelevant for parenterals

Correct Answer: Ionic strength influences drug solubility, protein stability, and electrostatic interactions

Q17. Which buffer has pKa near 4.76 and is commonly used in acidic formulations?

• Phosphate
• Acetate
• Borate
• Tris

Correct Answer: Acetate

Q18. Which buffer system is likely to absorb CO2 from air and change pH on standing or autoclaving?

• Phosphate buffer
• Bicarbonate-carbonic acid buffer
• Acetate buffer
• Borate buffer

Correct Answer: Bicarbonate-carbonic acid buffer

Q19. Buffer selection for ophthalmic solutions must consider:

• Only cost of buffer
• pH compatibility with tear pH, isotonicity, irritation potential, and stability
• Buffer color and odor only
• Only antimicrobial activity

Correct Answer: pH compatibility with tear pH, isotonicity, irritation potential, and stability

Q20. Which buffer is most suitable for buffering near pH 9 in certain topical or chemical processes?

• Borate buffer
• Acetate buffer
• Citrate buffer
• Phosphate buffer

Correct Answer: Borate buffer

Q21. A primary pharmaceutical reason to use a buffer in an IV formulation is to:

• Enhance color
• Maintain pH to minimize pain and tissue irritation and to ensure drug stability
• Promote crystallization
• Reduce sterility requirements

Correct Answer: Maintain pH to minimize pain and tissue irritation and to ensure drug stability

Q22. Which statement about buffer pH and temperature is true?

• Buffer pH is completely independent of temperature
• Some buffers show pH changes with temperature due to temperature dependence of pKa
• All buffers become more basic as temperature increases
• Temperature only affects ionic strength, not pH

Correct Answer: Some buffers show pH changes with temperature due to temperature dependence of pKa

Q23. In choosing a buffer for a formulation that contains calcium, which buffer might cause precipitation issues?

• Phosphate buffer with calcium
• Acetate buffer with calcium
• Borate buffer with calcium
• Histidine buffer with calcium

Correct Answer: Phosphate buffer with calcium

Q24. How does pH influence drug ionization and thus solubility?

• pH does not affect ionization
• Ionization depends on pH relative to pKa and alters solubility and permeability
• All drugs are equally soluble at any pH
• Only temperature affects ionization

Correct Answer: Ionization depends on pH relative to pKa and alters solubility and permeability

Q25. Which buffer is commonly avoided in mass spectrometry due to non-volatility?

• Ammonium formate
• Ammonium acetate
• Phosphate buffer
• Volatile organic acid buffers

Correct Answer: Phosphate buffer

Q26. The buffer capacity quantitatively reflects:

• The concentration of buffer required for a drug
• The resistance of pH to change upon addition of acid or base
• The color stability of the formulation
• The number of ions present

Correct Answer: The resistance of pH to change upon addition of acid or base

Q27. Which buffer is widely used in dissolution testing and HPLC mobile phases when a non-volatile buffer is acceptable?

• Phosphate buffer
• Ammonium hydroxide buffer
• Formic acid buffer
• Ammonium acetate buffer

Correct Answer: Phosphate buffer

Q28. During formulation development, why is buffer concentration kept as low as feasible while maintaining capacity?

• To save costs only
• To reduce ionic strength, minimize incompatibilities, and limit toxicity while ensuring sufficient buffering
• Because higher concentration reduces pH control
• To increase microbial growth

Correct Answer: To reduce ionic strength, minimize incompatibilities, and limit toxicity while ensuring sufficient buffering

Q29. Which buffer component is likely to be problematic in sterile parenteral products due to toxicity at higher concentrations?

• Phosphate at moderate concentrations
• Borate at high concentrations
• Sodium chloride
• Water

Correct Answer: Borate at high concentrations

Q30. What effect does adding a large amount of strong acid to a buffer have compared with adding it to pure water?

• The pH change is greater in buffer than in pure water
• The pH change is smaller in buffer than in pure water
• The pH change is identical in both
• The buffer will precipitate

Correct Answer: The pH change is smaller in buffer than in pure water

Q31. Which buffer is commonly used for nucleic acid and electrophoresis applications and has pKa around 8.1?

• Tris buffer
• Acetate buffer
• Phosphate buffer
• Borate buffer

Correct Answer: Tris buffer

Q32. How does ionic strength influence apparent pKa values in buffer solutions?

• Ionic strength has no effect on pKa
• Ionic strength can shift apparent pKa by altering activity coefficients
• Ionic strength always increases pKa
• Ionic strength neutralizes acids

Correct Answer: Ionic strength can shift apparent pKa by altering activity coefficients

Q33. Which buffer is often used for formulations requiring acidic pH around 3?

• Citrate buffer
• Phosphate buffer
• Tris buffer
• Borate buffer

Correct Answer: Citrate buffer

Q34. A formulation requires pH 7.2 and you choose phosphate buffer (pKa2 ≈ 7.2). If the molar ratio [HPO4^2-]/[H2PO4^-] = 1, what is the expected pH?

• 6.2
• 7.2
• 8.2
• 9.2

Correct Answer: 7.2

Q35. Which buffer property is most critical when designing an ophthalmic product to avoid irritation?

• Buffer color
• Buffer pH and isotonicity close to tear fluid
• Buffer cost
• Buffer odor

Correct Answer: Buffer pH and isotonicity close to tear fluid

Q36. For precise pH adjustment of a buffer during preparation, the recommended practical approach is to:

• Mix equimolar amounts of acid and base always
• Add strong acid or base to the weak acid or base solution and measure pH until desired value is reached
• Heat the solution to change pH
• Add salts arbitrarily without measuring pH

Correct Answer: Add strong acid or base to the weak acid or base solution and measure pH until desired value is reached

Q37. Which phenomenon explains why a buffer near its pKa resists pH changes most effectively?

• Maximum salt solubility
• Equal concentrations of acid and base provide maximal neutralization capacity for added acids or bases
• Temperature effects
• Surface tension changes

Correct Answer: Equal concentrations of acid and base provide maximal neutralization capacity for added acids or bases

Q38. Which buffer is commonly used in topical pharmaceutical formulations like mouthwashes due to mild alkalinity and safety?

• Sodium bicarbonate buffer
• Hydrochloric acid buffer
• Strong base buffer
• Phosphoric acid buffer

Correct Answer: Sodium bicarbonate buffer

Q39. In analytical assays, why might phosphate buffers interfere with certain enzyme reactions?

• Phosphate always enhances all enzymes
• Phosphate can bind to enzyme active sites or alter metal cofactor availability and inhibit activity
• Phosphate changes color of reagents only
• Phosphate sterilizes the solution

Correct Answer: Phosphate can bind to enzyme active sites or alter metal cofactor availability and inhibit activity

Q40. The term ‘buffer range’ refers to:

• The range of temperatures a buffer can withstand
• The pH interval over which the buffer effectively resists pH change, approximately pKa ±1
• The concentration range of the buffer components
• The shelf life of the buffer

Correct Answer: The pH interval over which the buffer effectively resists pH change, approximately pKa ±1

Q41. Which buffer choice is most appropriate to stabilize a formulation at pH 5?

• Borate buffer
• Citrate or acetate buffer
• Tris buffer
• Ammonium buffer at pH 9

Correct Answer: Citrate or acetate buffer

Q42. What is the likely effect on drug stability if the formulation pH drifts away from the optimum pH during storage?

• No effect on drug stability
• Potential increase in degradation such as hydrolysis or oxidation depending on pH sensitivity
• Only color changes will occur
• Drug will become more potent

Correct Answer: Potential increase in degradation such as hydrolysis or oxidation depending on pH sensitivity

Q43. Which buffer system would be least suitable for a formulation that must be sterile and filtered through a 0.22 μm membrane requiring low particulate and metal contaminants?

• Buffered with volatile ammonium salts
• Buffered with sterile pharmaceutical-grade salts like phosphate made from high-purity reagents
• Buffered with impure crude salts containing insoluble particulates
• Buffered with ultrapure reagents and filtered

Correct Answer: Buffered with impure crude salts containing insoluble particulates

Q44. Which buffer is commonly used in vaccine formulations to provide stability and low toxicity?

• Histidine buffer
• Strong mineral acid buffer
• High concentration phosphate at extreme pH
• Undiluted organic solvent

Correct Answer: Histidine buffer

Q45. The term ‘buffer capacity’ can be qualitatively increased by:

• Decreasing the total buffer concentration
• Increasing the total buffer concentration while maintaining desired pH
• Evaporating solvent
• Adding organic dyes

Correct Answer: Increasing the total buffer concentration while maintaining desired pH

Q46. Which of the following is true regarding buffer selection for HPLC methods coupled to mass spectrometry?

• Use non-volatile buffers like phosphate for best MS sensitivity
• Prefer volatile buffers like ammonium acetate or formate to avoid ion source contamination
• Buffer choice has no effect on MS performance
• Any surfactant-based buffer is ideal

Correct Answer: Prefer volatile buffers like ammonium acetate or formate to avoid ion source contamination

Q47. During autoclaving, which buffer type is most likely to undergo pH change due to loss or gain of CO2?

• Bicarbonate buffer
• Phosphate buffer
• Acetate buffer
• Borate buffer

Correct Answer: Bicarbonate buffer

Q48. How does buffer pH affect preservative efficacy in multi-dose pharmaceutical products?

• Preservative efficacy is pH-independent
• Preservatives often have optimal activity at specific pH ranges, so buffer pH can increase or decrease antimicrobial effectiveness
• Buffers destroy all preservatives
• Buffers convert preservatives into active drugs

Correct Answer: Preservatives often have optimal activity at specific pH ranges, so buffer pH can increase or decrease antimicrobial effectiveness

Q49. In controlled release systems where pH triggers drug release, buffers are used to:

• Only color the dosage form
• Create a microenvironmental pH that triggers polymer swelling or erosion and controls release
• Increase tablet hardness only
• Reduce the need for excipients

Correct Answer: Create a microenvironmental pH that triggers polymer swelling or erosion and controls release

Q50. Which buffer would be a logical first choice for an oral rinse designed to neutralize acids in the mouth and be safe for mucosal tissues?

• Concentrated hydrochloric acid solution
• Sodium bicarbonate buffer
• Strong alkaline buffer at pH 12
• High concentration phosphate buffer at pH 2

Correct Answer: Sodium bicarbonate buffer

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