To find the volume of cyclohexane needed, we can use the formula for density:
\[ \text{Density} = \frac{\text{Mass}}{\text{Volume}} \]
Rearranging this formula to solve for volume gives:
\[ \text{Volume} = \frac{\text{Mass}}{\text{Density}} \]
We are given:
- Mass of cyclohexane = 13.0 g
- Density of cyclohexane = 0.7781 g/mL
Now, we can calculate the volume:
\[ \text{Volume} = \frac{13.0 , \text{g}}{0.7781 , \text{g/mL}} \approx 16.7 , \text{mL} \]
Now, rounding to three significant figures, the volume of cyclohexane that should be used is:
\[ \boxed{16.7 , \text{mL}} \]