Question

1. at 298 k and 1 atm, br₂ is a liquid with a high vapor pressure, and cl₂ is a gas. these observations provide evidence that under the given conditions, the

(a) forces among br₂ molecules are stronger than those among cl₂ molecules
(b) forces among cl₂ molecules are stronger than the cl - cl bond
(c) br - br bond is stronger than the cl - cl bond
(d) cl - cl bond is stronger than the br - br bond

Explanation:

Step1: Analyze intermolecular forces

Intermolecular forces (London dispersion forces in this case as \(Br_2\) and \(Cl_2\) are non - polar) are related to the size of the molecules. Larger molecules (\(Br_2\) has a larger electron cloud than \(Cl_2\)) have stronger London dispersion forces.

Step2: Relate to physical state

Since \(Br_2\) is a liquid and \(Cl_2\) is a gas at the given conditions, the intermolecular forces among \(Br_2\) molecules are stronger (it takes more energy to overcome the forces to convert \(Br_2\) from liquid to gas than for \(Cl_2\)).

Step3: Analyze bond strength

Bond strength (\(Cl - Cl\) and \(Br - Br\)) is related to bond length and atomic size. \(Cl - Cl\) bond (\(r_{Cl}=0.99\space Å\)) is shorter than \(Br - Br\) bond (\(r_{Br}=1.42\space Å\)). Shorter bonds are stronger. So \(Cl - Cl\) bond is stronger than \(Br - Br\) bond.

Answer:

A. forces among \(Br_2\) molecules are stronger than those among \(Cl_2\) molecules