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 of a chemical. If the final volume of the solution needs to be 600 mL, how many grams of the chemical are required? (Assume 1 mL of solvent has a mass of 1 gram for percentage calculations.)
- A25 grams
- B1.5 grams
- C15 grams
- D6 grams
Show answer & explanationAnswer & explanation
Correct answer: C. 15 grams
A 2.5% concentration means 2.5 grams of chemical per 100 mL of solution. To find the amount needed for 600 mL, set up a proportion: (2.5 g / 100 mL) = (x g / 600 mL). Solving for x, x = (2.5 * 600) / 100 = 1500 / 100 = 15 grams.
Why the other options are wrong
- A. This answer might result from multiplying 2.5 by 10 or an incorrect understanding of percentage.
- B. This answer is a miscalculation, possibly dividing by 1000 instead of 100 or an incorrect initial percentage conversion.
- D. This answer might result from calculating 2.5% of 600 and then dividing by 10 or a similar error.
Percentage Concentration (w/v)
The ratio of the mass of solute (in grams) to the volume of solution (in milliliters), expressed as a percentage.
- Expressed as % (w/v) = (grams of solute / mL of solution) * 100.
- Used for preparing solutions where a specific weight of substance is dissolved in a given volume.
- Assumes 1 mL of solvent approximates 1 gram for practical calculations.
Memory trick: Percent means Parts per Hundred, so set up your ratio and solve it.