What is the number of formula units in a 9.30 mol sample of FeCl3?

Iwould you figure it out but you don't have a picture or in your question as to what the physical property you're looking for is

Vander waals forces are inter molecular bonds that exist within molecules of the same substance. a water molecule is made up of oxygen and hydrogen atoms which share electrons between each other. the vander waals forces are forces that exist between multitude of different  molecules of water. dipole dipole forces is the type of vander waals force that exist in water. the oxygen atom which is more electronegative pulls the shared electron closer to itself thus generating a partial negative charge while the hydrogen acquire a partial positive charge. these two different charges causes attraction to occur in water molecules.

Visible light is located in the middle of the spectrum.

Ibelieve it would be hcl