Question

You have been assigned to prepare 50.0 mL of a 3.0 %(v/v) solution in a volumetric flask from a 20.0% (v/v) Red Food Coloring (RFC) stock solution provided. Use the equation below to calculate the amount in (mL) of the RFC stock solution to prepare your assigned % solution.

Answer 1

7.5mL of the stock solution

Step-by-step explanation:

A stock solution is a concentrated solution that is used to make another more diluted solution.

In the problem, the RFC solution is 20% (v/v). That means contains 20mL of RFC in 100mL of solution.

Yo need to prepare 50.0mL of a 3.0% (v/v), solution (3mL of RFC in 100mL of solution). That means you need:

50.0mL solution × (3mL RFC / 100mL solution) = 1.5mL of RFC. These RFC must come from the stock solution

As your stock solution contains 20mL of RFC per 100mL of solution, you will need:

1.5mL RFC × (100mL stock / 20mL RFC) =

7.5mL of the stock solution