273g/25 mL = 10.92 (that's the density)
What has a density of 10.92 grams/mL? I don't know but I bet it's in your notes or on the worksheet.
You have to find the gram formula mass of C6H6 then do mass (g) = mol x GFM
The group of elements that have some properties of metals and some properties of nonmetals are called metalloids.