Particle number MCQs With Answer

Understanding particle number is essential for B. Pharm students because it links the microscopic world of molecules to practical pharmaceutical calculations. The mole concept and Avogadro’s number (6.022×10²³) are central to converting between particles, moles, and grams for drug formulation, compounding, and quality control. Mastery of mole-to-mass conversions, molarity, formula units, and particle counts helps in accurate dosage calculations, titration, and interpreting analytical results. These topics directly impact pharmaceutical calculations, stability studies, and nanomedicine dosing. This collection of MCQs goes deeper into computational and conceptual aspects relevant to pharmacy practice. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the value of Avogadro’s number commonly used in calculations?

• 6.022 × 10²⁰
• 6.022 × 10²³
• 3.1416 × 10²³
• 1.6605 × 10^-24

Correct Answer: 6.022 × 10²³

Q2. How many particles are present in 2 moles of a substance?

• 3.011 × 10²³
• 6.022 × 10²³
• 1.2044 × 10²⁴
• 2.4088 × 10²³

Correct Answer: 1.2044 × 10²⁴

Q3. How many molecules are there in 36 g of water? (Molar mass H₂O = 18 g/mol)

• 1.5055 × 10²³
• 3.011 × 10²³
• 6.022 × 10²³
• 1.2044 × 10²⁴

Correct Answer: 1.2044 × 10²⁴

Q4. In an ionic solid like NaCl, the most appropriate term for the “particle” is:

• Molecule
• Ion pair
• Formula unit
• Atomic cluster

Correct Answer: Formula unit

Q5. One mole of any substance contains:

• One gram of the substance
• Avogadro’s number of particles
• The molecular weight in grams always
• One liter at STP

Correct Answer: Avogadro’s number of particles

Q6. How many moles are represented by 1.2044 × 10²⁴ molecules?

• 0.2 mol
• 1 mol
• 2 mol
• 10 mol

Correct Answer: 2 mol

Q7. How many atoms are present in 0.5 mol of H₂O molecules?

• 3.011 × 10²³ atoms
• 6.022 × 10²³ atoms
• 9.033 × 10²³ atoms
• 1.2044 × 10²⁴ atoms

Correct Answer: 9.033 × 10²³ atoms

Q8. How many molecules are in 250 mL of a 0.1 M solution?

• 6.022 × 10²²
• 1.5055 × 10²²
• 2.4088 × 10²³
• 3.011 × 10²³

Correct Answer: 1.5055 × 10²²

Q9. What mass of glucose (M = 180 g/mol) corresponds to 0.2 mol?

• 9 g
• 18 g
• 36 g
• 90 g

Correct Answer: 36 g

Q10. 6.022 × 10²³ atoms of carbon represent how many moles?

• 0.5 mol
• 1 mol
• 6.022 mol
• 12 mol

Correct Answer: 1 mol

Q11. How many oxygen atoms are present in 2 moles of CO₂ molecules?

• 1.2044 × 10²⁴
• 2.4088 × 10²⁴
• 6.022 × 10²³
• 3.011 × 10²³

Correct Answer: 2.4088 × 10²⁴

Q12. How many particles are in 5 mmol of a substance?

• 3.011 × 10²⁰
• 3.011 × 10²¹
• 3.011 × 10²²
• 3.011 × 10²³

Correct Answer: 3.011 × 10²¹

Q13. What is the correct formula to calculate moles from mass?

• moles = mass × molar mass
• moles = mass / molar mass
• moles = molar mass / mass
• moles = mass × Avogadro’s number

Correct Answer: moles = mass / molar mass

Q14. In solid sodium chloride, the “particle” count for converting to moles should be based on which entity?

• Individual sodium and chloride atoms separately
• NaCl formula units
• NaCl molecules held together
• Crystal lattice as a single particle

Correct Answer: NaCl formula units

Q15. Avogadro’s number is primarily used to convert between:

• Grams and liters
• Moles and particles
• Pressure and volume
• Concentration and mass

Correct Answer: Moles and particles

Q16. How many molecules are present in 0.125 mol of a drug?

• 7.5275 × 10²²
• 1.5055 × 10²²
• 9.033 × 10²²
• 6.022 × 10²²

Correct Answer: 7.5275 × 10²²

Q17. One mole of an ideal gas at STP occupies approximately:

• 22.4 L
• 1 L
• 24.0 L
• 0.0821 L

Correct Answer: 22.4 L

Q18. How many atoms are present in one mole of S₈ molecules?

• 6.022 × 10²³
• 4.8176 × 10²⁴
• 3.011 × 10²³
• 1.2044 × 10²⁴

Correct Answer: 4.8176 × 10²⁴

Q19. For nanoparticle dosing, particle number is especially important because:

• Mass alone determines biological effect
• Particle count affects surface area and biological interaction
• Molarity cannot be used for nanoparticles
• Particle number is always negligible

Correct Answer: Particle count affects surface area and biological interaction

Q20. What mass of a compound with molar mass 150 g/mol contains 3.011 × 10²³ particles?

• 25 g
• 50 g
• 75 g
• 150 g

Correct Answer: 75 g

Q21. Approximately how many moles are represented by 1.0 × 10²⁰ molecules?

• 1.66 × 10^-4 mol
• 1.66 × 10^-3 mol
• 6.02 × 10^-4 mol
• 1.0 × 10^-2 mol

Correct Answer: 1.66 × 10^-4 mol

Q22. How many total ions result from complete dissociation of 0.5 mol of MgCl₂?

• 3.011 × 10²³ ions
• 6.022 × 10²³ ions
• 9.033 × 10²³ ions
• 1.2044 × 10²⁴ ions

Correct Answer: 9.033 × 10²³ ions

Q23. How many electrons are in 1 mole of neutral hydrogen atoms?

• 0 electrons
• 6.022 × 10²³ electrons
• 1.2044 × 10²⁴ electrons
• 3.011 × 10²³ electrons

Correct Answer: 6.022 × 10²³ electrons

Q24. When calculating particle numbers in solution, why must you consider dissociation for electrolytes?

• Dissociation changes the molar mass
• Dissociation increases the solvent volume
• Dissociation changes the number of particles affecting osmolarity and concentration
• Dissociation removes Avogadro’s number from use

Correct Answer: Dissociation changes the number of particles affecting osmolarity and concentration

Q25. How many molecules are there in 90 g of water? (Molar mass H₂O = 18 g/mol)

• 3.011 × 10²⁴
• 1.5055 × 10²⁴
• 6.022 × 10²³
• 5.033 × 10²³

Correct Answer: 3.011 × 10²⁴

Q26. How many molecules are present in 1 L of a 2.0 M solution?

• 1.2044 × 10²⁴
• 6.022 × 10²³
• 3.011 × 10²³
• 2.4088 × 10²⁴

Correct Answer: 1.2044 × 10²⁴

Q27. A tablet contains 500 mg of drug with molar mass 250 g/mol. How many molecules does it contain?

• 2.4088 × 10²¹
• 1.2044 × 10²¹
• 1.2044 × 10²⁰
• 3.011 × 10²¹

Correct Answer: 1.2044 × 10²¹

Q28. The empirical formula mass compared to the molecular mass helps determine:

• Avogadro’s number
• The molecular formula as an integer multiple of the empirical formula
• The percentage yield of a reaction
• Melting point of a compound

Correct Answer: The molecular formula as an integer multiple of the empirical formula

Q29. Which statement correctly defines Avogadro’s number historically?

• The number of atoms in 1 g of hydrogen
• The number of particles in 12 g of carbon-12
• The number of molecules in 22.4 L of gas at STP
• The number of atoms in one liter of gas

Correct Answer: The number of particles in 12 g of carbon-12

Q30. Why is mastery of particle number and mole calculations crucial for B. Pharm students?

• It is only theoretical and rarely applied
• It underpins drug dose calculations, compound preparation, and quality control in pharmaceutics
• It replaces the need for experimental assays
• It is only relevant to organic chemistry

Correct Answer: It underpins drug dose calculations, compound preparation, and quality control in pharmaceutics

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