Final answer:
Use Raoult's law for an ideal solution of similar components (b) and Henry's law for dilute solutions or where a gas is dissolved in a liquid (a) and (c).
Step-by-step explanation:
When determining which law to use for vapor-liquid equilibrium calculations, the choice between Raoult's law and Henry's law depends on the nature of the components in the solution and their interactions. Raoult's law is typically used for components in an ideal solution, where the intermolecular forces between dissimilar molecules are similar to those between similar molecules.
(a) For a solution of water and dissolved nitrogen, Henry's law is used since nitrogen is a non-volatile solute in water and the solution is dilute. Answer: "H"
(b) For a mixture of hexane, octane, and decane, which are similar non-polar hydrocarbons that would form nearly ideal solutions, Raoult's law is applicable. Answer: "R"
(c) For CO2 dissolved in water in club soda or other carbonated beverages, Henry's law is used because CO2 is a gas dissolving in a liquid at relatively low concentrations. Answer: "H"