Now assume you measure out exactly 2.0 ml of aluminum chloride into a third test tube. how many moles of aluminum chloride are in the tube?

First, convert 2.0 mL of AlCl3 to grams using the density, which is 2.48g/mL. So 2.48g/mL * 2.0 mL = 4.96g. Then find the molar mass of aluminum chloride and divide 4.96 by this number, which is 133.34g. 4.96g*(1mol/133.34g) = .0372 mols AlCl3. Check for significant digits though.