We can find the number of moles using the molarity formula:
[tex]\text{Molarity}=\frac{moles}{volume\text{ (liters)}}.[/tex]
We have to convert 250 mL to L. Remember that 1 liter equals 1000 mL:
[tex]250\text{ mL}\cdot\frac{1\text{ L}}{1000\text{ mL}}=0.25\text{ L.}[/tex]
Now, that we have the value of volume in liters (0.25 L) and the molarity (0.0666 M (mol/L) ), we can clear in the formula for moles and replace the given values:
[tex]\begin{gathered} \text{moles}=\text{Molarity}\cdot\text{volume,} \\ \text{moles}=0.0666\frac{mol}{L}\cdot0.25L, \\ \text{moles}=0.0166\text{ moles=1.66}\cdot10^{-2}moles. \end{gathered}[/tex]
The answer is that we have 1.66 x 10^(-2) moles in 0.25 L of 0.0666 M of CH3CH2Cl.
