Question

take a look at the pairs of molecules having dipole - dipole interactions to the right. which of the following are true? hydrogens are the positive dipoles of all the molecules. the oxygen, nitrogen, and fluorine atoms are the negative dipoles of the molecules. the major force at play between the molecules is induced dipole - dipole. the electronegativity of nitrogen and hydrogen is the same. either oxygen, nitrogen, or fluorine are the positive dipoles of the molecules.

Explanation:

• In polar molecules with dipole - dipole interactions (like \(H_2O\), \(NH_3\), \(HF\) shown in the diagram), hydrogen has a lower electronegativity than oxygen, nitrogen, and fluorine. So, hydrogen acts as the positive dipole (\(H\) has a partial positive charge \(\delta+\)) and oxygen, nitrogen, and fluorine act as the negative dipoles (\(O\), \(N\), \(F\) have partial negative charges \(\delta-\)).
• Induced dipole - dipole (London dispersion forces) are not the major force here. The major force is permanent dipole - dipole (in the case of \(H_2O - H_2O\), \(NH_3 - NH_3\), \(HF - HF\) interactions shown, and hydrogen bonding which is a special case of strong dipole - dipole interaction).
• The electronegativity of nitrogen (\(3.04\)) and hydrogen (\(2.20\)) is not the same.
• Oxygen, nitrogen, and fluorine are the negative dipoles, not the positive dipoles.

Answer:

• Hydrogens are the positive dipoles of all the molecules. (True)
• The oxygen, nitrogen, and fluorine atoms are the negative dipoles of the molecules. (True)