Data:
[tex]M_{concentrated} = 2.5\:mol[/tex]
[tex]V_{concentrated} = ?[/tex]
[tex]M_{dilute} = 0.50\:mol[/tex]
[tex]V_{dilute} = 100\:mL\to0.100\:L[/tex]
Formula: Dilution Calculations
[tex]M_{concentrated} * V_{concentrated} = M_{dilute} * V_{dilute} [/tex]
Solving:
[tex]M_{concentrated} * V_{concentrated} = M_{dilute} * V_{dilute} [/tex]
[tex]2.5 * V_{concentrated} = 0.50 * 0.100 [/tex]
[tex]2.5V_{concentrated} = 0.05[/tex]
[tex]V_{concentrated} = \frac{0.05}{2.5} [/tex]
[tex]\boxed{\boxed{V_{concentrated} = 0.02\:L\:or\:20\:mL}} \end{array}}\qquad\quad\checkmark[/tex]