Answer:
Of the following substances, <u>PCl₃</u> has the highest boiling point
Explanation:
The given substances and their boiling point from online resources are;
Krypton, Kr, boiling point = -153.4°C
Chlorine gas, Cl₂, boiling point = -34.6°C
Borane, BH₃, (transient compound), boiling point of the dimer it forms B₂H₆ = -164.85°C
Methane, CH₄, boiling point = -161.6°C
Phosphorus trichloride, PCl₃, boiling point = 76.1°C
Therefore, given that PCl₃ is a volatile liquid at room temperature, while the other substances are gases and that PCl₃ has the highest boiling point of all the substances of 76.1°C, the substance with the highest boiling point is PCl₃.