NAPLEX (North American Pharmacist Licensure Examination) Practice Exam

Disable ads (and more) with a membership for a one time $4.99 payment

Ace your North American Pharmacist Licensure Examination (NAPLEX) with our comprehensive practice test. Features include interactive flashcards, multiple-choice questions, with detailed hints and explanations. Fast-track your pharmacy career today!

Practice this question and more.

How is osmolality (mOsmol/L) calculated?

Q1 / C1 = Q2 / C2
Wt of substance (g/L) / MW (g/mole) * (#particles) * 1000
Q2 * C1 = Q1 * C2
E = (58.5)(i) / (MW of drug)(1.8)

The correct answer is: Wt of substance (g/L) / MW (g/mole) * (#particles) * 1000

Osmolality is a measure of the number of osmotically active particles per kilogram of solvent. The correct formula to calculate osmolality is given by option B: Wt of substance (g/L) / MW (g/mole) * (#particles) * 1000. This formula takes into account the weight of the substance (in grams per liter), the molecular weight of the substance (in grams per mole), the number of particles formed when the substance dissolves, and multiplies it by 1000 to convert the result to milliosmoles per liter (mOsmol/L). Option A (Q1 / C1 = Q2 / C2) represents the formula for dilution calculations, not osmolality. Option C (Q2 * C1 = Q1 * C2) represents the formula for concentration calculations using a dilution factor, not osmolality. Option D (E = (58.5)(i) / (MW of drug)(1.8)) is the formula for calculating the equivalent weight of a drug in a specific salt form and is not related to osmolality calculation.