Ineed a through d, i have no idea on what i'm supposed to do

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

What is the enthalpy of combustion (per mole) of c4h10 (g)? –2,657.5 kj/mol –5315.0 kj/mol –509.7 kj/mol –254.8 kj/mol

Which of the four hypothetical substances you investigated would be most harmful to living organisms? 50 points!