NAPLEX Flashcards: Compounding Ingredient Quantities

What this deck covers

This deck focuses on Compounding Ingredient Quantities, giving you a quick way to review the definitions, rules, and examples that matter most for NAPLEX.

How to use these flashcards

Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: What is the formula to convert percent strength (%w/v) to ratio strength $1:x$?

Answer: $x = \frac{100}{\%w/v}$. Rearranges percent strength to find x in 1:x ratio by dividing 100 by the percentage.

Flashcard 2: What is the formula to calculate grams from moles using molecular weight (MW)?

Answer: $g = mol \times MW$. Determines mass in grams by multiplying moles by molecular weight.

Flashcard 3: What is the formula to find grams of solute for a %w/w preparation from total grams?

Answer: $g_{solute} = \frac{\%w/w}{100} \times g_{total}$. Derives from the definition of %w/w as the mass of solute per 100 grams of total preparation.

Flashcard 4: What is the formula to calculate milliequivalents (mEq) from mg, MW, and valence?

Answer: $mEq = \frac{mg \times valence}{MW}$. Computes milliequivalents accounting for ion valence and molecular weight from milligrams.

Flashcard 5: What is the formula to calculate mg from mEq, MW, and valence?

Answer: $mg = \frac{mEq \times MW}{valence}$. Solves for milligrams using milliequivalents, molecular weight, and ion valence.

Flashcard 6: Identify the method to find ingredient amount when potency is not 100% (assay given).

Answer: $\text{Weigh} = \frac{\text{required amount}}{\text{assay fraction}}$. Adjusts the weighed amount to compensate for less than 100% potency as indicated by assay.

Flashcard 7: What volume of solute is needed to prepare $80\,mL$ of a $10\%\,v/v$ solution?

Answer: $8\,mL$. Based on %v/v: 10% means 10 mL solute per 100 mL total, for 80 mL.

Flashcard 8: What mass of solute is needed to prepare $120\,mL$ of a $2\%\,w/v$ solution?

Answer: $2.4\,g$. Applies %w/v definition: 2% means 2 g per 100 mL, scaled to 120 mL.

Flashcard 9: What mass of solute is needed to prepare $250\,g$ of a $5\%\,w/w$ ointment?

Answer: $12.5\,g$. Uses %w/w: 5% means 5 g solute per 100 g total, applied to 250 g.

Flashcard 10: What is the formula to calculate aliquot volume needed to deliver a target mass from a solution?

Answer: $V = \frac{Dose}{C}$. Determines the volume required to deliver a specific dose based on solution concentration.

Flashcard 11: What is the formula for dilution using concentrations and volumes (all in consistent units)?

Answer: $C_1V_1 = C_2V_2$. Applies the principle that the amount of solute remains constant before and after dilution.

Flashcard 12: What is the formula to adjust for hydrate/anhydrous forms using molecular weights?

Answer: $g_{needed} = g_{target} \times \frac{MW_{available}}{MW_{target}}$. Corrects for differences in molecular weights between available and target forms of the compound.

Flashcard 13: What is the formula to convert ratio strength $1:x$ (w/v) to percent strength?

Answer: $\%w/v = \frac{100}{x}$. Converts ratio strength where 1 part solute in x parts solution equals 100/x percent.

Flashcard 14: What mass should be weighed to obtain $500\,mg$ active if assay is $80\%$?

Answer: $625\,mg$. Divides required active amount by assay fraction (0.8) to find weighed mass.

Flashcard 15: What is the formula to find mL of solute for a %v/v preparation from total mL?

Answer: $mL_{solute} = \frac{\%v/v}{100} \times mL_{total}$. Stems from %v/v as the volume of solute per 100 mL of total solution volume.

Flashcard 16: How many milligrams of drug are in $30\,g$ of a $1.5\%\,w/w$ cream?

Answer: $450\,mg$. Uses %w/w: 1.5% means 1.5 g per 100 g, for 30 g converted to mg.

Flashcard 17: What ratio strength $1:x$ is equivalent to $2\%\,w/v$?

Answer: $1:50$. Converts 2% w/v to ratio 1:x by dividing 100 by 2.

Flashcard 18: What volume of a $1\,mg/mL$ solution provides a $0.25\,mg$ dose?

Answer: $0.25\,mL$. Calculates volume as dose divided by concentration to deliver required amount.

Flashcard 19: What volume of a $20\%$ stock is needed to make $300\,mL$ of a $5\%$ solution?

Answer: $75\,mL$. Uses dilution formula $C_1V_1 = C_2V_2$ to find stock volume needed.

Flashcard 20: How many grams of drug are in $45\,mL$ of a $4\%\,w/v$ solution?

Answer: $1.8\,g$. Applies %w/v: 4% means 4 g per 100 mL, scaled to 45 mL.

Flashcard 21: What is the formula for alligation to find parts of high strength needed: $parts_{high}$?

Answer: $parts_{high} = C_{target} - C_{low}$. In alligation, parts of higher concentration equal the difference between target and lower concentration.

Flashcard 22: What is the percent strength (%w/v) equivalent of ratio strength $1:250$ (w/v)?

Answer: $0.4\%\,w/v$. Converts 1:250 ratio to percent by dividing 100 by 250.

Flashcard 23: What is the formula to calculate moles from grams using molecular weight (MW)?

Answer: $mol = \frac{g}{MW}$. Calculates the number of moles by dividing mass in grams by molecular weight.

Flashcard 24: What is the formula for alligation to find parts of low strength needed: $parts_{low}$?

Answer: $parts_{low} = C_{high} - C_{target}$. In alligation, parts of lower concentration equal the difference between higher and target concentration.

Flashcard 25: What is the formula to find grams of solute for a %w/v preparation from total mL?

Answer: $g_{solute} = \frac{\%w/v}{100} \times mL_{total}$. Based on %w/v definition as grams of solute per 100 mL of total solution volume.