Introduction: Ion exchange resins are crosslinked polymeric beads (commonly polystyrene‑divinylbenzene) bearing ionizable functional groups that exchange ions with surrounding media. Key properties include exchange capacity (meq/g), selectivity, degree of crosslinking, water uptake, kinetics, and stability. Mechanistically, ion exchange proceeds by reversible equilibrium influenced by charge, hydrated radius, pH, ionic strength, and Donnan effects. In pharmaceutics, resins are essential for drug‑resin complexation, taste masking, controlled‑release formulations, purification, and metal removal. Understanding strong versus weak, cation versus anion exchangers, regeneration, and analytical determination (titration, capacity tests) is vital for B.Pharm students. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the primary definition of an ion exchange resin?
- Synthetic polymer beads bearing ionizable functional groups that exchange ions with solution
- Natural polymers that dissolve to release ions
- Inorganic salts that swap covalent bonds with solutes
- Membranes that allow only neutral molecules to pass
Correct Answer: Synthetic polymer beads bearing ionizable functional groups that exchange ions with solution
Q2. Which two main classes describe ion exchange resins?
- Hydrophobic and hydrophilic resins
- Cation exchange and anion exchange resins
- Organic and inorganic resins
- Porous and non‑porous resins
Correct Answer: Cation exchange and anion exchange resins
Q3. What matrix is most commonly used for pharmaceutical ion exchange resins?
- Polyethylene glycol
- Polystyrene‑divinylbenzene (PS‑DVB)
- Cellulose acetate
- Polyvinyl alcohol
Correct Answer: Polystyrene‑divinylbenzene (PS‑DVB)
Q4. Which functional group is typical for strong cation exchange resins?
- Carboxylic acid (-COOH)
- Sulfonic acid (-SO3H)
- Quaternary ammonium
- Thiourea
Correct Answer: Sulfonic acid (-SO3H)
Q5. What functional group characterizes strong anion exchange resins?
- Sulfonate groups
- Primary amines
- Quaternary ammonium groups
- Carboxylate groups
Correct Answer: Quaternary ammonium groups
Q6. What is the usual unit for expressing ion exchange capacity?
- mg/mL
- mL/g
- milliequivalents per gram (meq/g)
- molarity (M)
Correct Answer: milliequivalents per gram (meq/g)
Q7. Which compound is commonly used as the crosslinking agent in PS‑DVB resins?
- Ethylene glycol
- Divinylbenzene (DVB)
- Polyethylene glycol
- Glycidyl methacrylate
Correct Answer: Divinylbenzene (DVB)
Q8. How does increasing crosslinking (DVB %) affect resin properties?
- Increases swelling and decreases mechanical strength
- Decreases swelling and increases mechanical strength
- Has no effect on swelling or strength
- Makes resins soluble in water
Correct Answer: Decreases swelling and increases mechanical strength
Q9. Which factors primarily determine ion selectivity of a resin?
- Resin color and manufacturing date
- Ion charge (valency), hydrated radius, and functional group affinity
- Only the resin particle size
- The solvent viscosity only
Correct Answer: Ion charge (valency), hydrated radius, and functional group affinity
Q10. What is the Donnan potential in ion exchange systems?
- The mechanical pressure inside resin beads
- The potential difference across resin‑solution interface due to fixed charges
- The pH at which half the functional groups are ionized
- The voltage required to regenerate a resin
Correct Answer: The potential difference across resin‑solution interface due to fixed charges
Q11. Which reagent is typically used to regenerate a cation exchange resin to the H+ form?
- Sodium hydroxide (NaOH)
- Hydrochloric acid (HCl)
- Sodium chloride (NaCl)
- Ammonium hydroxide (NH4OH)
Correct Answer: Hydrochloric acid (HCl)
Q12. Which reagent regenerates a strong anion exchange resin to the OH− form?
- Hydrochloric acid (HCl)
- Sulfuric acid (H2SO4)
- Sodium hydroxide (NaOH)
- Sodium sulfate (Na2SO4)
Correct Answer: Sodium hydroxide (NaOH)
Q13. What aspect of resin design determines its total exchange capacity?
- Particle color
- Density of ionizable functional groups per unit mass
- Ambient light during storage
- Amount of residual solvent
Correct Answer: Density of ionizable functional groups per unit mass
Q14. The ion exchange process is best described as:
- An irreversible chemical reaction forming covalent bonds
- A reversible equilibrium process involving exchange of counter‑ions
- Physical adsorption only, without ion transfer
- Thermal decomposition of the polymer
Correct Answer: A reversible equilibrium process involving exchange of counter‑ions
Q15. Which pharmaceutical application commonly uses ion exchange resins?
- As primary solvents for injectable formulations
- Taste masking and controlled‑release through drug‑resin complexes
- To increase volatility of drugs
- As non‑ionic surfactants
Correct Answer: Taste masking and controlled‑release through drug‑resin complexes
Q16. How do drug‑resin complexes (resinate) typically modify drug release?
- They make drugs completely insoluble and inactive
- They provide ion‑exchange controlled release, releasing drug in exchange for cations/anions in GI fluids
- They instantly liberate drug upon contact with saliva only
- They chemically transform drug into a new compound
Correct Answer: They provide ion‑exchange controlled release, releasing drug in exchange for cations/anions in GI fluids
Q17. How does particle size of resin affect exchange kinetics?
- Smaller particles decrease exchange rate due to aggregation
- Smaller particles increase exchange rate by reducing diffusion path length
- Particle size has no impact on kinetics
- Larger particles always provide faster exchange
Correct Answer: Smaller particles increase exchange rate by reducing diffusion path length
Q18. How does solution pH influence weak ion exchange resins?
- pH has no effect on weak resins
- pH affects the ionization state of weak functional groups, altering capacity and selectivity
- Only temperature influences weak resins
- Weak resins dissolve at neutral pH
Correct Answer: pH affects the ionization state of weak functional groups, altering capacity and selectivity
Q19. Which functional group is characteristic of weak acid cation exchange resins?
- Sulfonic acid (-SO3H)
- Carboxylic acid (-COOH)
- Quaternary ammonium (-NR4+)
- Phosphate ester
Correct Answer: Carboxylic acid (-COOH)
Q20. A common laboratory method to determine resin exchange capacity is:
- UV‑Vis spectroscopy without extraction
- Gravimetric drying only
- Titration of exchanged ions after displacement
- Measuring color change of the resin
Correct Answer: Titration of exchanged ions after displacement
Q21. Which processes commonly control the rate of ion exchange in beads?
- Chemical decomposition and vaporization
- Film diffusion and pore (intra‑particle) diffusion
- Only convective flow outside the bead
- Gravitational settling inside columns
Correct Answer: Film diffusion and pore (intra‑particle) diffusion
Q22. How does increasing ionic strength of the solution generally affect ion exchange selectivity?
- Enhances selectivity for low‑valency ions
- Has no effect on exchange behavior
- Reduces selectivity by competing counter‑ions and screening charges
- Permanently increases resin capacity
Correct Answer: Reduces selectivity by competing counter‑ions and screening charges
Q23. Why is pKa of functional groups important for weak ion exchangers?
- It determines mechanical strength
- It dictates the ionization extent at given pH, affecting capacity and exchange behavior
- It controls polymer crosslinking density
- It only affects color of the resin
Correct Answer: It dictates the ionization extent at given pH, affecting capacity and exchange behavior
Q24. Which of the following is an example of a commercial strong cation exchange resin used in pharmaceuticals?
- Amberlite IRP‑69
- Amberlite IR120 (H+ form)
- Activated charcoal
- Polyethylene glycol 400
Correct Answer: Amberlite IR120 (H+ form)
Q25. Which is an example of a commonly used strong anion exchange resin?
- Amberlite IRA‑400 (Cl− form)
- Amberlite XAD‑2
- Amberlite IR120 (Na+ form)
- Calcium carbonate
Correct Answer: Amberlite IRA‑400 (Cl− form)
Q26. In cation exchange chromatography, which ion would generally be retained strongest?
- Na+ (monovalent)
- Ca2+ (divalent)
- Cl− (anion)
- H2O (neutral)
Correct Answer: Ca2+ (divalent)
Q27. How does increasing temperature typically affect ion exchange processes?
- Always decreases both exchange rate and capacity
- Generally increases exchange kinetics though selectivity may change
- Has no effect on either rate or equilibrium
- Makes resins dissolve in water
Correct Answer: Generally increases exchange kinetics though selectivity may change
Q28. What distinguishes chelating resins from conventional ion exchange resins?
- Chelating resins bind specific metal ions via multidentate ligand groups
- Chelating resins are purely hydrophobic adsorbents
- Conventional resins form covalent bonds with metals
- Chelating resins are used only for organic molecules
Correct Answer: Chelating resins bind specific metal ions via multidentate ligand groups
Q29. Which parameter describes the water content retained by a resin bead?
- Exchange capacity (meq/g)
- Water retention or moisture content (percentage)
- pKa value of functional groups
- Ion valency
Correct Answer: Water retention or moisture content (percentage)
Q30. Why is the aromatic polystyrene backbone advantageous for PS‑DVB resins?
- It makes resins highly biodegradable
- It provides chemical and thermal stability and a hydrophobic matrix for functionalization
- It prevents any ion exchange from occurring
- It makes resins soluble in water for easy injection
Correct Answer: It provides chemical and thermal stability and a hydrophobic matrix for functionalization
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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