(a) What atoms must a molecule contain to participate in hydrogen bonding with other molecules of the same kind? (b) Which of the following molecules can form hydrogen bonds with other molecules of the same kind: $\mathrm{CH}_{3} \mathrm{~F}, \mathrm{CH}_{3} \mathrm{NH}_{2}, \mathrm{CH}_{3} \mathrm{OH}, \mathrm{CH}_{3} \mathrm{Br} ?$

To participate in hydrogen bonding, a molecule must have a hydrogen atom bonded to a highly electronegative element, usually nitrogen (N), oxygen (O), or fluorine (F). This creates a highly polar bond, enabling the positive hydrogen end to attract the negative end of another molecule containing N, O, or F.

Now, let's examine each of the given molecules and determine if they can form hydrogen bonds with other molecules of the same kind. 1. \(\mathrm{CH}_{3}\mathrm{F}\): This molecule has a hydrogen atom, but it is not bonded to the highly electronegative fluorine (F) atom. The hydrogen atoms are bonded to carbon (C), which is less electronegative. Therefore, this molecule cannot form hydrogen bonds with other molecules of the same kind. 2. \(\mathrm{CH}_{3}\mathrm{NH}_{2}\): Here, the hydrogen atoms are bonded to a highly electronegative nitrogen (N) atom. As a result, this molecule can participate in hydrogen bonding with other molecules of the same kind. 3. \(\mathrm{CH}_{3}\mathrm{OH}\): In this case, the hydrogen atom is bonded to a highly electronegative oxygen (O) atom, allowing this molecule to form hydrogen bonds with other molecules of the same kind. 4. \(\mathrm{CH}_{3}\mathrm{Br}\): This molecule has a hydrogen atom, but it is not bonded to a highly electronegative atom. The hydrogen atoms are bonded to carbon (C), and bromine (Br) is less electronegative than N, O, or F. Therefore, this molecule cannot form hydrogen bonds with other molecules of the same kind.

In summary, a molecule must have a hydrogen atom bonded to nitrogen (N), oxygen (O), or fluorine (F) to participate in hydrogen bonding with other molecules of the same kind. Out of the given molecules, \(\mathrm{CH}_{3}\mathrm{NH}_{2}\) and \(\mathrm{CH}_{3}\mathrm{OH}\) can form hydrogen bonds with other molecules of the same kind, while \(\mathrm{CH}_{3}\mathrm{F}\) and \(\mathrm{CH}_{3}\mathrm{Br}\) cannot.