Answer: Acetone has the following density,
[tex]784\operatorname{kg}/m^3[/tex]Therefore we have:
[tex]\begin{gathered} 16.86ml=10^{-6}m^3 \\ m=\frac{(784kg)}{m^3}\times10^{-6}m^3=0.000784kg \\ \therefore\rightarrow \\ m=0.784\cdot1000\text{grams}=13.21824g \end{gathered}[/tex]