we dont know
Density is calculated as mass divided by volume. In this case, the mass of the silicon sample is 820g and the volume of the container is 350 cm^3. Therefore, the density of the silicon sample in the container is 820g / 350 cm^3 = 2.34 g/cm^3.
There are 350 mL in 350 cm3, as 1 cm3 is equivalent to 1 mL.