Determination of ash and volatile matter MCQs With Answer

Introduction

This quiz collection on Determination of Ash and Volatile Matter is designed for M.Pharm students studying Herbal and Cosmetic Analysis (MPA 204T). It focuses on theoretical principles, pharmacopoeial procedures, instrumentation, calculations, and interpretation of results related to total ash, acid‑insoluble ash, water‑soluble ash, sulphated ash, and volatile matter/loss on drying. Questions range from methodology and sample preparation to common errors, significance for herbal drugs, and routine troubleshooting. Use these MCQs to deepen understanding, prepare for practical exams, and reinforce concepts used in quality control of herbal materials and finished products.

Q1. What is the primary purpose of determining total ash in a herbal drug?

• To measure the organic volatile constituents lost on heating
• To estimate the total amount of inorganic residue remaining after incineration
• To determine the content of volatile oils in the sample
• To quantify the bacterial contamination of the drug

Correct Answer: To estimate the total amount of inorganic residue remaining after incineration

Q2. Which apparatus is most appropriate for ashing organic herbal material to constant weight?

• Hot plate with beaker
• Muffle furnace
• Vacuum oven
• Rotary evaporator

Correct Answer: Muffle furnace

Q3. At approximately what temperature range are most herbal samples ignited to determine total ash according to common pharmacopoeial practice?

• 100–110 °C
• 250–300 °C
• 450–600 °C
• 800–900 °C

Correct Answer: 450–600 °C

Q4. How is acid‑insoluble ash obtained during ash analysis?

• By igniting the sample with concentrated nitric acid directly
• By boiling the total ash with dilute hydrochloric acid, filtering and igniting the residue
• By dissolving the ash in water and igniting the filtrate
• By mixing ash with sulfuric acid and heating to dryness

Correct Answer: By boiling the total ash with dilute hydrochloric acid, filtering and igniting the residue

Q5. What does a high acid‑insoluble ash value most commonly indicate in a powdered herbal drug?

• High content of volatile oils
• Adulteration or contamination with earthy materials such as silica or sand
• High carbohydrate content
• Excess residual moisture

Correct Answer: Adulteration or contamination with earthy materials such as silica or sand

Q6. How is water‑soluble ash defined in relation to total ash?

• The fraction of total ash that remains insoluble in cold acetone
• The fraction of total ash soluble in boiling water
• The fraction of total ash remaining after treatment with concentrated sulfuric acid
• The volatile part of ash lost on ignition

Correct Answer: The fraction of total ash soluble in boiling water

Q7. Which crucible material is preferred to avoid introducing extraneous silica during ash determination?

• Glass crucible
• Porcelain crucible
• Sapphire crucible
• Quartz or silica crucible

Correct Answer: Porcelain crucible

Q8. What is the correct formula to calculate percent total ash of a sample?

• (Weight of sample / Weight of ash) × 100
• ((Weight of ash − Weight of crucible) / Weight of sample) × 100
• ((Weight of crucible − Weight of ash) / Weight of sample) × 100
• ((Weight of sample − Weight of ash) / Weight of ash) × 100

Correct Answer: ((Weight of ash − Weight of crucible) / Weight of sample) × 100

Q9. Which of the following best distinguishes ‘loss on drying’ (LOD) from ‘volatile matter’ determination?

• LOD measures only inorganic residue; volatile matter measures organic residue
• LOD measures weight loss at a relatively low temperature (e.g., 105 °C) often representing water; volatile matter on ignition measures loss at higher temperatures representing volatile organic constituents
• LOD requires acid treatment while volatile matter does not
• They are identical procedures with different names

Correct Answer: LOD measures weight loss at a relatively low temperature (e.g., 105 °C) often representing water; volatile matter on ignition measures loss at higher temperatures representing volatile organic constituents

Q10. Which step helps prevent loss of fine ash particles during transfer and weighing?

• Use of open petri dishes for cooling
• Allowing crucible to cool in a desiccator before weighing
• Cooling in ambient air on bench to speed up the process
• Weighing immediately while still hot

Correct Answer: Allowing crucible to cool in a desiccator before weighing

Q11. Sulphated ash is particularly useful for which type of sample or analysis?

• Quantifying volatile oils in essential oils
• Determining ash in certain drug preparations and excipients where organic carbon may persist; it provides reproducible inorganic residue by adding sulfuric acid before ignition
• Measuring microbiological contamination
• Assessing moisture content at 105 °C

Correct Answer: Determining ash in certain drug preparations and excipients where organic carbon may persist; it provides reproducible inorganic residue by adding sulfuric acid before ignition

Q12. A student observes a dark brown residue after ashing herbal sample; what is the most likely cause?

• Complete combustion of all organic matter
• Incomplete ignition or presence of charred carbon due to insufficient temperature or time
• Excessive contamination by inorganic salts
• Use of wet crucible for weighing

Correct Answer: Incomplete ignition or presence of charred carbon due to insufficient temperature or time

Q13. Which of the following is a common source of error leading to falsely high ash values?

• Incomplete drying of sample before ashing
• Contamination of crucible with dust or residue from previous use
• Over-ignition at excessively high temperature that volatilizes inorganic salts
• Using too small a sample mass

Correct Answer: Contamination of crucible with dust or residue from previous use

Q14. In determining water‑soluble ash, which operation is essential after boiling ash with water?

• Direct ignition of the boiled mixture without filtration
• Filtering and igniting the insoluble residue, then subtracting its weight from total ash
• Neutralizing the solution with base and measuring conductivity
• Cooling and measuring pH of the filtrate

Correct Answer: Filtering and igniting the insoluble residue, then subtracting its weight from total ash

Q15. Which analytical balance accuracy is generally required for ash determination in pharmacopoeial procedures?

• Accuracy to 1 g
• Accuracy to 0.1 g
• Accuracy to 0.01 g (10 mg) or better
• Accuracy to 1 kg

Correct Answer: Accuracy to 0.01 g (10 mg) or better

Q16. What is the appropriate way to report ash results to ensure reproducibility?

• Report only the percent ash without experimental details
• Include sample weight, crucible tare, ignition temperature and time, and final ash weight in the report
• Report ash as qualitative “high” or “low”
• Report only raw weights without calculations

Correct Answer: Include sample weight, crucible tare, ignition temperature and time, and final ash weight in the report

Q17. For volatile matter determination by loss on drying, which drying condition is most commonly used in pharmacopeial methods?

• Drying at room temperature for 1 hour
• Drying at 105 °C to constant weight
• Drying at 300 °C to constant weight
• Drying under UV light until color changes

Correct Answer: Drying at 105 °C to constant weight

Q18. When calculating percent volatile matter, which expression is correct?

• (Final weight / Initial weight) × 100
• ((Initial weight − Final weight) / Initial weight) × 100
• ((Initial weight + Final weight) / Initial weight) × 100
• ((Final weight − Initial weight) / Final weight) × 100

Correct Answer: ((Initial weight − Final weight) / Initial weight) × 100

Q19. Why is it important to cool crucibles in a desiccator before weighing ash residue?

• To allow chemical reactions to complete
• To prevent moisture uptake from ambient air and ensure accurate weighing
• To oxidize the ash further
• To remove volatile salts by condensation

Correct Answer: To prevent moisture uptake from ambient air and ensure accurate weighing

Q20. In herbal quality control, which combination of ash values is most indicative of contamination with earthy matter?

• Low total ash and low acid‑insoluble ash
• High total ash with high acid‑insoluble ash
• High water‑soluble ash and low total ash
• High sulphated ash and low acid‑insoluble ash

Correct Answer: High total ash with high acid‑insoluble ash

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