ATI TEAS (Test of Essential Academic Skills) Version 7ScienceMedium
A laboratory technician is preparing a solution for an experiment. They need to create 250 mL of a 0.5 M solution of sodium chloride (NaCl) from a 2.0 M stock solution. What volume of the stock solution is required?
- A31.25 mL
- B500 mL
- C62.5 mL
- D125 mL
Show answer & explanationAnswer & explanation
Correct answer: C. 62.5 mL
The dilution formula M1V1 = M2V2 is used. Given M1 = 2.0 M, V2 = 250 mL, and M2 = 0.5 M. Solving for V1: V1 = (M2V2) / M1 = (0.5 M * 250 mL) / 2.0 M = 125 / 2 = 62.5 mL.
Why the other options are wrong
- A. This is incorrect; it might result from an arithmetic error or incorrect formula application.
- B. This is incorrect; it might result from multiplying M1 by V2.
- D. This is incorrect; it might result from dividing V2 by M1 in some way.
Dilution Formula (M1V1=M2V2)
The dilution formula M1V1 = M2V2 is used to calculate the volume or concentration of a solution before or after dilution, where M is molarity and V is volume.
- M1 = initial concentration, V1 = initial volume.
- M2 = final concentration, V2 = final volume.
- Units for volume must be consistent (e.g., both mL or both L).
Memory trick: Mighty Vials Make Mighty Volumes.