What is the formula for phosphorus pentafluoride?

If a || b and e || f, what is the value of y ?

What is the strongest intermolecular force between an nacl unit and an h2o molecule together in a solution? covalent bonding dipole-dipole force hydrogen bonding ion-dipole force

If a plot weight (in g) vs. volume (in ml) for a metal gave the equation y= 13.41x and r^2=0.9981 what is the density of the metal?