# Question #91c2b

Apr 22, 2017

$19.0 m L$

#### Explanation:

First, find the moles of NaOH(aq) needed to create the 100.0 mL of 0.020 M NaOH(aq) solution.

$m o l s N a O H \left(a q\right) = M o l a r i t y \cdot L i t e r s$

$m o l s N a O H \left(a q\right) = 0.020 M \cdot 0.1000 L$

$m o l s N a O H \left(a q\right) = 0.002 m o l s$

Now that you know how many moles you need, find many mL of 0.105 M NaOH(aq) solution is needed in order to have 0.002 moles.

$\text{Liters" = "moles NaOH(aq)"/"Molarity}$

$\text{Liters" = "0.002 moles NaOH(aq)"/"0.105 M NaOH(aq)}$

$\text{Liters} = 0.0190476$

Since you have 3 significant figures the answer would be $0.0190 L$, or:

$19.0 m L$