Question

A 10.0 Molar solution is used to make 100. mL a 5.00 Molar solution. How much of the original solution is used?

Answer 1

Data: 
$M_{concentrated} = 10\:mol$
$V_{concentrated} = ?$
$M_{dilute} = 5\:mol$
$V_{dilute} = 100\:mL$

Formula: Dilution Calculations

$M_{concentrated} * V_{concentrated} = M_{dilute} * V_{dilute}$

Solving:


$M_{concentrated} * V_{concentrated} = M_{dilute} * V_{dilute}$
$10 * V_{concentrated} = 5 * 100$
$10V_{concentrated} = 500$
$V_{concentrated} = \frac{500}{10}$
$\boxed{\boxed{V_{concentrated} = 50\:mL}} \end{array}}\qquad\quad\checkmark$

Answer:
B. 50.0 mL