Question

Br2 and Cl2 can react to form the compound BrCl. The vapor pressure of Br2 is 52 torr, whereas the vapor pressure of BrCl is 178 torr. Explain this difference in vapor pressure in terms of all the intermolecular forces present between molecules of each substance.

Answer 1

Explanation:The difference in vapor pressure between Br2 and BrCl can be explained by the differences in their intermolecular forces. Br2 has only London dispersion forces present between its molecules, whereas BrCl has both London dispersion forces and dipole-dipole interactions due to its polar nature.

The presence of dipole-dipole interactions in BrCl makes it more difficult for its molecules to escape into the gas phase, leading to a lower vapor pressure compared to Br2. Additionally, BrCl has a higher molecular weight than Br2, which also contributes to its lower vapor pressure as heavier molecules tend to have weaker intermolecular forces and lower vapor pressures.

Overall, the higher vapor pressure of Br2 can be attributed to its weaker intermolecular forces compared to BrCl.