Hydrogenation of oils MCQs With Answer is an essential review for B. Pharm students studying lipid chemistry, excipient formulation, and pharmaceutical processing. This concise, keyword-rich introduction covers hydrogenation mechanisms, catalysts (Ni, Pd), partial versus complete hydrogenation, trans fat formation, iodine value changes, and industrial and laboratory techniques. Understanding hydrogenated vegetable oils, reaction conditions, analytical tests, and health implications helps pharmacy students choose suitable excipients and ensure product stability. These MCQs target core concepts, calculations, process control, and safety aspects to prepare you for exams and practical applications. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. What is the primary chemical change during the hydrogenation of vegetable oils?
- Addition of hydrogen across carbon-carbon double bonds
Correct Answer: Addition of hydrogen across carbon-carbon double bonds
Q2. Which catalyst is most commonly used industrially for hydrogenation of oils?
Correct Answer:
Q3. Partial hydrogenation of unsaturated fats often leads to formation of which isomer?
Correct Answer: Trans double bonds
Q4. Which analytical value decreases as oils are hydrogenated and unsaturation is reduced?
Correct Answer:
Q5. In the mechanism of catalytic hydrogenation, what role does the metal surface play?
Correct Answer: Activates hydrogen and adsorbs the alkene for hydrogen addition
Q6. Which factor increases the rate of hydrogenation of an oil?
Correct Answer: Higher temperature within catalyst stability limits
Q7. Which of the following is NOT a common hydrogenation catalyst support?
Correct Answer: Sodium chloride
Q8. What is the typical purpose of partial hydrogenation in the food and pharmaceutical industries?
Correct Answer: To increase melting point and stability of fats without full saturation
Q9. Which experimental apparatus is commonly used for laboratory hydrogenation reactions?
Correct Answer:
Q10. Which parameter is most directly affected when converting liquid oil into a semisolid hydrogenated product?
Correct Answer: Melting point
Q11. Trans fats formed during hydrogenation are associated with increased risk of which health problem?
Correct Answer: Cardiovascular disease
Q12. Which measurement quantifies the amount of unsaturation remaining after hydrogenation?
Correct Answer: Iodine value
Q13. What is the effect of hydrogenation on oxidative stability of oils?
Correct Answer: Increases stability by reducing unsaturation
Q14. Which gas is required for the hydrogenation reaction?
Correct Answer: Hydrogen
Q15. Which of the following is a sign of catalyst poisoning during hydrogenation?
Correct Answer: Decreased reaction rate despite available hydrogen
Q16. Which step is critical to avoid excessive trans fat formation during hydrogenation?
Correct Answer: Controlling reaction time and degree of conversion
Q17. Which spectroscopic technique is commonly used to analyze fatty acid composition after hydrogenation?
Correct Answer: Gas chromatography (GC) of fatty acid methyl esters
Q18. Hydrogenation converts cis double bonds to which configurations if isomerization occurs?
Correct Answer: Trans double bonds
Q19. What is the main industrial benefit of fully hydrogenating oils for pharmaceutical excipients?
Correct Answer: Enhancing oxidative stability and shelf life of excipients
Q20. Which pretreatment can deactivate catalyst poisons before hydrogenation?
Correct Answer: Degassing to remove oxygen and sulfur compounds
Q21. Which metal catalyst is favored for selective hydrogenation of polyunsaturated fatty acids to monoenes?
Correct Answer: Palladium on barium sulfate (Rosenmund type)
Q22. In hydrogenation kinetics, which order of reaction is often assumed for hydrogen uptake when hydrogen concentration is constant?
Correct Answer: Zeroth order with respect to substrate
Q23. What is hydrogenolysis in context of hydrogenation processes?
Correct Answer: Cleavage of carbon-carbon or carbon-heteroatom bonds by hydrogen
Q24. Which parameter indicates the acidity of free fatty acids in hydrogenated oils?
Correct Answer: Acid value
Q25. Which additive is sometimes used to improve selectivity and reduce trans formation during hydrogenation?
Correct Answer: Benzoquinone or modifiers that inhibit isomerization
Q26. The iodine value is expressed in terms of grams of iodine absorbed per 100 g of oil; what does a lower iodine value indicate after hydrogenation?
Correct Answer: Lower unsaturation
Q27. Which safety hazard is most relevant when performing hydrogenation at scale?
Correct Answer: Flammability and explosion risk of hydrogen gas
Q28. What is the purpose of using supports like alumina for nickel catalysts?
Correct Answer: To disperse and stabilize the active metal, increasing surface area
Q29. Which technique helps quantify trans fatty acid content after hydrogenation?
Correct Answer: Gas chromatography with specific FA standards
Q30. Which factor promotes faster isomerization (cis to trans) during hydrogenation?
Correct Answer: Catalysts with high hydrogenation activity at high temperature
Q31. Which hydrogenation outcome is desirable for producing a pharmaceutical ointment base?
Correct Answer: Controlled partial hydrogenation to achieve desired consistency and melting profile
Q32. What is the role of pressure in hydrogenation reactions?
Correct Answer: Higher hydrogen pressure increases hydrogen solubility and rate
Q33. Which by-product can form during hydrogenation if polymerization occurs?
Correct Answer: Higher molecular weight polymers increasing viscosity
Q34. For quality control, which test assesses oxidative rancidity in hydrogenated oils?
Correct Answer: Peroxide value
Q35. Which statement about complete hydrogenation is correct?
Correct Answer: It converts all double bonds to single bonds, yielding a fully saturated fat
Q36. Which operating parameter is adjusted to stop hydrogenation at a desired degree?
Correct Answer: Removing H2 supply and separating catalyst at target iodine value
Q37. Hydrogenated vegetable oils used as excipients are chosen for which property?
Correct Answer: Certain melting point, consistency, and oxidative stability
Q38. What chemical change increases the melting point during hydrogenation?
Correct Answer: Increased saturation and straight-chain packing
Q39. Which condition favors cis-to-trans isomerization rather than full hydrogenation?
Correct Answer: Low catalyst activity and long contact times
Q40. What is a common method to remove catalyst particles after hydrogenation?
Correct Answer: Filtering or centrifugation while hot
Q41. Hydrogenation of oils is exothermic or endothermic?
Correct Answer: Exothermic
Q42. Which functional group is directly affected during oil hydrogenation?
Correct Answer: Allylic double bonds (C=C) in fatty acid chains
Q43. Why is palladium sometimes preferred for selective hydrogenation over nickel?
Correct Answer: Palladium allows hydrogenation at lower temperatures and greater selectivity
Q44. What is the typical effect of hydrogenation on color and odor of oils?
Correct Answer: Decreases off-odors and may lighten color due to removal of unsaturated chromophores
Q45. During hydrogenation, isomerization can be catalyzed by the metal surface leading to which intermediate?
Correct Answer: Carbocationic intermediate transiently stabilized on the metal surface
Q46. What analytical change indicates completion of hydrogenation in a lab-scale reactor?
Correct Answer: Hydrogen uptake plateaus and iodine value reaches target
Q47. Which pharmaceutical product class commonly uses hydrogenated vegetable oils as bases or fillers?
Correct Answer: Oral tablets and suppositories as base or binder
Q48. What is a possible environmental concern with industrial hydrogenation?
Correct Answer: Disposal and recovery of metal catalysts and solvent emissions
Q49. How can manufacturers minimize trans fat content while still improving oil stability?
Correct Answer: Use interesterification or enzymatic modification instead of partial hydrogenation
Q50. In calculating hydrogen uptake, what stoichiometric change corresponds to hydrogenating one double bond per fatty acid chain?
Correct Answer: Addition of one mole of H2 per mole of double bond
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