# Question #e0ae8

Jun 9, 2017

$20. \text{mL}$ should be correct.

#### Explanation:

This a dilution problem, so we can use the formula

${M}_{\text{conc"V_ "conc" = M_ "dil"V_ "dil}}$

where

• ${M}_{\text{conc}}$ is the molar concentration (molarity) of the concentrated, stock solution, and ${M}_{\text{dil}}$ is the molar concentration of the dilute solution

• ${V}_{\text{conc}}$ is the volume of the concentrated, stock solution, and ${V}_{\text{dil}}$ is the volume of the dilute solution

Let's rearrange the equation to solve for the volume of the stock solution, ${V}_{\text{conc}}$, and plug in our known values:

${V}_{\text{conc" = (M_ "dil"V_ "dil")/(M_ "conc") = ((0.50cancel(M))(100.0"mL"))/(2.5cancel(M)) = color(red)(20."mL}}$