Problem: The table below shows some physical properties of halogenated liquids.LiquidExperimental Dipole Moment (D)Normal Boiling Point (˚C)CH2F21.93–52CH2Cl21.6040CH2Br21.4397Which of the following statements best explains these data?(a) The larger the dipole moment, the stronger the intermolecular forces, and therefore the boiling point is lowest for the molecule with the largest dipole moment.(b) The dispersion forces increase from F to Cl to Br; since the boiling point also increases in this order, the dispersion forces must make a far greater contribution to intermolecular interactions than dipole–dipole interactions.(c) The trend in electronegativity is F > Cl > Br; therefore, the most ionic compound (CH2F2) has the lowest boiling point, and the most covalent compound (CH2Br2) has the highest boiling point.(d) Boiling point increases with molecular weight for these nonpolar compounds.

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FREE Expert Solution

(a) The larger the dipole moment, the stronger the intermolecular forces, and therefore the boiling point is lowest for the molecule with the largest dipole moment.

• CH2F2 has the largest dipole moment (strongest intermolecular forces) but has the lowest boiling point
• CH2F2 has the smallest dipole moment (weakest intermolecular forces) but has the highest boiling point

The statement does not explain the data.


(b) The dispersion forces increase from F to Cl to Br; since the boiling point also increases in this order, the dispersion forces must make a far greater contribution to intermolecular interactions than dipole–dipole interactions.

• dispersion forces increase with size
• size increases from F to Cl to Br
• dispersion forces increase from F to Cl to Br

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Problem Details
The table below shows some physical properties of halogenated liquids.
LiquidExperimental Dipole Moment (D)Normal Boiling Point (˚C)
CH2F21.93–52
CH2Cl21.6040
CH2Br21.4397


Which of the following statements best explains these data?
(a) The larger the dipole moment, the stronger the intermolecular forces, and therefore the boiling point is lowest for the molecule with the largest dipole moment.
(b) The dispersion forces increase from F to Cl to Br; since the boiling point also increases in this order, the dispersion forces must make a far greater contribution to intermolecular interactions than dipole–dipole interactions.
(c) The trend in electronegativity is F > Cl > Br; therefore, the most ionic compound (CH2F2) has the lowest boiling point, and the most covalent compound (CH2Br2) has the highest boiling point.
(d) Boiling point increases with molecular weight for these nonpolar compounds.

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Based on our data, we think this problem is relevant for Professor Cole & Geng & Lovander's class at IOWA.