Determination of saponification value MCQs With Answer

Introduction

This blog provides a focused set of multiple-choice questions on the determination of saponification value tailored for M.Pharm students studying Herbal and Cosmetic Analysis (MPA 204T). The questions cover theoretical foundations, practical assay steps, reagent selection, calculations, typical values for oils, common sources of error, and interpretation of results in formulation and quality control. Each MCQ is designed to test understanding of principles (e.g., relationship between chain length and saponification value), practical laboratory skills (titration technique, blank correction), and data calculation (use of titration volumes, normality and constants). Answers are given for self-assessment and exam preparation.

Q1. What does the saponification value (SV) of an oil represent?

• The mass of KOH (mg) required to neutralize free fatty acids in 100 g of oil
• The mg of KOH required to esterify glycerol in 1 g of oil
• The mg of KOH required to hydrolyze and neutralize all esters in 1 g of oil
• The volume of ethanolic KOH solution needed to dissolve 1 g of oil

Correct Answer: The mg of KOH required to hydrolyze and neutralize all esters in 1 g of oil

Q2. What are the usual units reported for saponification value?

• mg HCl per g of sample
• mg KOH per g of sample
• mL NaOH per g of sample
• mmol of fatty acid per kg of sample

Correct Answer: mg KOH per g of sample

Q3. Which reagent is typically used as the saponifying reagent in the standard SV assay?

• Standardized ethanolic KOH solution
• Aqueous NaOH solution
• Standardized ethanolic HCl solution
• Saturated sodium chloride solution

Correct Answer: Standardized ethanolic KOH solution

Q4. What is the primary purpose of running a blank parallel to the sample during SV determination?

• To measure the free fatty acid content of the solvent
• To account for KOH consumption by reagents and solvent
• To calibrate the balance used for weighing the sample
• To confirm the sample contains triglycerides

Correct Answer: To account for KOH consumption by reagents and solvent

Q5. Which indicator is commonly used to detect the end point when titrating excess KOH in the SV test?

• Methyl orange
• Bromothymol blue
• Phenolphthalein
• Litmus paper

Correct Answer: Phenolphthalein

Q6. Which of the following formulas correctly represents the calculation for saponification value (SV)?

• SV = (Vblank – Vsample) × N × 56.1 / W
• SV = (Vsample – Vblank) × N × 56.1 × W
• SV = (Vblank + Vsample) / (N × 56.1 × W)
• SV = (Vsample + Vblank) × 56.1 / N

Correct Answer: SV = (Vblank – Vsample) × N × 56.1 / W

Q7. In the SV equation, what does the constant 56.1 represent?

• Molecular weight of glycerol (g/mol)
• Equivalent weight of HCl in mg
• Milligrams of KOH per millimole (molecular weight of KOH)
• Volume of ethanolic KOH in mL

Correct Answer: Milligrams of KOH per millimole (molecular weight of KOH)

Q8. A higher saponification value indicates which property of the fatty acids in the triglyceride?

• Longer average chain length
• Higher degree of unsaturation
• Lower average molecular weight (shorter chain length)
• Higher free fatty acid content

Correct Answer: Lower average molecular weight (shorter chain length)

Q9. Which of these oils would you expect to have the highest saponification value?

• Olive oil (predominantly C18 fatty acids)
• Coconut oil (high proportion of C8–C12 fatty acids)
• Soybean oil (predominantly C18 polyunsaturated)
• Beef tallow (longer chain saturated fatty acids)

Correct Answer: Coconut oil (high proportion of C8–C12 fatty acids)

Q10. If you accidentally under-reflux the sample (insufficient saponification time), what is the most likely effect on the measured SV?

• Measured SV will be higher than true value
• Measured SV will be lower than true value
• No effect on measured SV
• Measured SV will be exactly double the true value

Correct Answer: Measured SV will be lower than true value

Q11. Which procedural error would produce an erroneously high saponification value?

• Using a KOH solution whose concentration is lower than assumed
• Over-titrating the excess alkali (adding too much acid)
• Not correcting for the blank
• Weighing too large a sample without adjusting formula

Correct Answer: Not correcting for the blank

Q12. During SV test the excess KOH is titrated with standard acid. Which acid is most commonly used?

• Standardized sulfuric acid
• Standardized hydrochloric acid
• Standardized acetic acid
• Standardized phosphoric acid

Correct Answer: Standardized hydrochloric acid

Q13. What is the typical normality of ethanolic KOH used for saponification in many pharmacopeial methods?

• 0.1 N
• 0.5 N
• 1.0 N
• 2.0 N

Correct Answer: 0.5 N

Q14. How does the presence of free fatty acids (FFA) in the sample affect the saponification value result?

• FFA have no influence on SV because SV measures only esters
• FFA increase the apparent SV because extra KOH is required to neutralize them
• FFA decrease SV because they prevent saponification
• FFA cause the SV to become zero

Correct Answer: FFA increase the apparent SV because extra KOH is required to neutralize them

Q15. Which instrument or technique can be used as an alternative to classical titration for determining saponification value in research labs?

• Gas chromatography of liberated glycerol
• Turbidimetric assay of soaps
• Potentiometric titration
• UV-Vis spectrophotometry of fatty acid chromophores

Correct Answer: Potentiometric titration

Q16. What is the relationship between saponification value (SV) and mean molecular weight (M) of the fatty acid chains in triglycerides (approximate qualitative)?

• SV is directly proportional to M
• SV is inversely proportional to M
• SV is equal to M divided by 100
• SV and M are unrelated

Correct Answer: SV is inversely proportional to M

Q17. Why is alcohol (ethanol) used as the solvent in the saponification reaction?

• Ethanol reacts with KOH to form a stronger base
• Ethanol dissolves both oil and KOH, promoting contact for saponification
• Ethanol prevents the formation of glycerol
• Ethanol acts as the titrant for the back titration

Correct Answer: Ethanol dissolves both oil and KOH, promoting contact for saponification

Q18. Which of the following best explains why shorter-chain fatty acids give a higher saponification value?

• Shorter chains have fewer ester linkages per molecule
• Shorter chains have lower molecular weight, so more molecules per gram, requiring more KOH per gram to saponify
• Shorter chains are more unsaturated, so they react faster with KOH
• Shorter chains evaporate during reflux increasing titrant consumption

Correct Answer: Shorter chains have lower molecular weight, so more molecules per gram, requiring more KOH per gram to saponify

Q19. In quality control of cosmetic oils, why is monitoring saponification value important?

• It indicates concentration of preservatives
• It helps detect adulteration and changes in average chain length or composition
• It measures the optical purity of fatty acids
• It determines the antioxidant capacity of the oil

Correct Answer: It helps detect adulteration and changes in average chain length or composition

Q20. Which procedural modification would help ensure complete saponification of hard-to-hydrolyze esters?

• Lower the reaction temperature during reflux
• Shorten the reflux time
• Use a larger excess of standardized ethanolic KOH and extend reflux time
• Avoid using a blank to simplify calculations

Correct Answer: Use a larger excess of standardized ethanolic KOH and extend reflux time

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