Question

Between Br₂ and I₂, who has the higher evaporation pressure, and why?

A) Br₂; due to its larger molecular size.
B) I₂; due to its smaller molecular size.
C) Br₂; due to its smaller molecular size.
D) I₂; due to its larger molecular size.

Answer 1

Iodine (I₂) has a higher evaporation pressure compared to bromine (Br₂) due to its larger molecular size and stronger dispersion forces.

Step-by-step explanation:

Between Br₂ and I₂, iodine (Ⅰ₂) has the higher evaporation pressure because it has larger and heavier molecules, which lead to stronger dispersion forces. It is known from the properties of halogens that as the atomic weight and size increase, the dispersion forces become stronger, which corresponds to a higher boiling point and lower vapor pressure for the molecule in its liquid state. Iodine (Ⅰ₂) exhibits stronger intermolecular forces and hence has a lower tendency to vaporize at the same temperature compared to bromine (Br₂), making iodine's evaporation pressure lower, and correspondingly its boiling point higher.