PTCB Certified Pharmacy Technician (PTCE)Order Entry and ProcessingMedium
A pharmacy technician is asked to prepare 500 mL of a 0.9% NaCl solution. How many grams of NaCl are needed?
- A0.9 grams
- B0.45 grams
- C9 grams
- D4.5 grams
Show answer & explanationAnswer & explanation
Correct answer: D. 4.5 grams
A 0.9% solution means 0.9 grams of solute per 100 mL of solution. To find the grams needed for 500 mL: (0.9 g / 100 mL) * 500 mL = 4.5 grams.
Why the other options are wrong
- A. This is the amount in 100 mL, not 500 mL.
- B. This would be for 50 mL of solution.
- C. This would be for 1000 mL (1 liter) of solution.
Percent Strength Calculation (w/v)
Calculations involving percent strength (weight/volume) to determine the amount of solute needed to prepare a specific volume of solution.
- Percent (w/v) means grams per 100 mL.
- Use ratio-proportion or dimensional analysis.
- Ensure units are consistent before calculation.
Memory trick: Concentration: Percent Means Per Hundred, Dose is Desired Amount.