Answer:
250 mL
Explanation:
These are the variable one has to have in mind:
[tex]C_1[/tex] = 16 M
[tex]C_{2}[/tex] = 2 M
[tex]V_{2}[/tex] = 2 L = 2000 mL
Note: C = concentration; V = volume; subscript 1 = stock solution; subscript = 2 = dilution.
What we have to solve is for [tex]V_{1}[/tex]
Use the following equation:
[tex]C_{1}[/tex] x [tex]V_{1}[/tex] = [tex]C_{2}[/tex] x [tex]V_{2}[/tex] ⇒ [tex]V_{1}[/tex] = [tex]\frac{2M x 2000 mL}{16M}[/tex] ⇒  [tex]V_{1}[/tex] = 250 mL
