Question

which substance would you most likely need to cool to the lowest temperature before it condenses?
ammonia (nh₃), a polar covalent compound
ethane (c₂h₆), a nonpolar covalent compound
potassium bromide (kbr), an ionic compound

Explanation:

Intermolecular forces affect boiling and condensation points. Non - polar covalent compounds have the weakest London dispersion forces. Ethane, being a non - polar covalent compound, has weaker intermolecular forces compared to polar covalent (ammonia with hydrogen bonding) and ionic (KBr with strong electrostatic forces) compounds. Weaker forces mean a lower condensation temperature.

Answer:

ethane (C₂H₆), a nonpolar covalent compound