ATI TEAS (Test of Essential Academic Skills) Version 7MathematicsMedium
A medical laboratory technician is preparing a solution. They need to create a 2.5% concentration by weight/volume (w/v) of a substance. If the final volume of the solution needs to be 500 mL, how many grams of the substance are required?
- A12.5 g
- B5 g
- C25 g
- D2.5 g
Show answer & explanationAnswer & explanation
Correct answer: A. 12.5 g
A 2.5% (w/v) solution means there are 2.5 grams of substance per 100 mL of solution. To find the grams needed for 500 mL, set up a proportion or multiply the percentage (as a decimal) by the total volume, then convert to grams.
Why the other options are wrong
- B. This is an incorrect calculation, possibly dividing 500 by 100 and then incorrectly multiplying by 2.5.
- C. This would be for a 5% (w/v) solution in 500 mL, or a 2.5% solution in 1000 mL.
- D. This would be for a 100 mL solution at 2.5% concentration.
Percentage Concentration (w/v)
A measure of concentration expressed as the number of grams of solute per 100 milliliters of solution.
- Units are grams (g) for solute and milliliters (mL) for solution.
- Formula: (grams of solute / mL of solution) * 100%.
- Commonly used in medical and pharmaceutical preparations.
Memory trick: Grams per Hundred Milli, That's the Ratio, See!