Chapter 5

For which of the following molecules will dipoledipole interactions be important: (a) \(\mathrm{CH}_{4} ;\) (b) \(\mathrm{CH}_{3} \mathrm{Cl}\); (c) \(\mathrm{CH}_{2} \mathrm{Cl}_{2}\); (d) \(\mathrm{CHCl}_{3}\); (e) \(\mathrm{CCl}_{4}\) ?

For which of the following molecules and ions will dipole-dipole interactions be important: (a) \(\mathrm{SF}_{4}\); (b) \(\mathrm{PF}_{5} ;\) (c) \(\mathrm{PF}_{3} ;\) (d) \(\mathrm{SF}_{4}\) ?

Place the following types of molecular and ion interactions in order of increasing magnitude: (a) iondipole; (b) induced dipole-induced dipole; (c) dipoledipole in the gas phase; (d) ion-ion; (e) dipole-dipole in the solid phase.

Explain why ionic solids like \(\mathrm{NaCl}\) have high melting points yet dissolve readily in water, whereas network solids like diamond have very high melting points and do not dissolve.

Which of the following moiecules are likely to form hydrogen bonds: (a) \(\mathrm{HF}\); (b) \(\mathrm{CH}_{4}\); (c) \(\mathrm{NH}_{3}\); (d) \(\mathrm{CH}_{3} \mathrm{OH}\) ?

Which of the following molecules are likely to form hydrogen bonds: (a) \(\mathrm{D}_{2} \mathrm{O}\); (b) \(\mathrm{CH}_{3} \mathrm{COOH}\); (c) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\); (d) \(\mathrm{H}_{3} \mathrm{PO}_{4}\) ?

Suggest, giving reasons, which substance in each pair is likely to have the higher melting point (Lewis structures may help your arguments): (a) HCl or NaCl; (b) \(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{OC}_{2} \mathrm{H}_{3}\) (diethyl ether) or \(\mathrm{C}_{4} \mathrm{H}_{9} \mathrm{OH}\) (butanol); (c) \(\mathrm{HF}\) or \(\mathrm{HCl}\); (d) \(\mathrm{H}_{2} \mathrm{O}\) or \(\mathrm{CH}_{3} \mathrm{OH}\).

Suggest, giving reasons, which substance in each pair is likely to have the higher boiling point: (a) \(\mathrm{H}_{2} \mathrm{~S}\) or \(\mathrm{H}_{2} \mathrm{O}\); (b) \(\mathrm{NH}_{3}\) or \(\mathrm{PH}_{3}\); (c) \(\mathrm{KBr}\) or \(\mathrm{CH}_{3} \mathrm{Br}\); (d) \(\mathrm{CH}_{4}\) or \(\mathrm{SiH}_{4}\) *

Predict which substanoe has the greater viscosity in its liquid form at \(0^{\circ} \mathrm{C}\) : (a) ethanol, \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\), or dimethyl ether, \(\mathrm{CH}_{3} \mathrm{OCH}_{3}\); (b) butane, \(\mathrm{C}_{4} \mathrm{H}_{10}\) or propanone, \(\mathrm{CH}_{3} \mathrm{COCH}_{3}\).

Potassium crystallizes in a bce structure. The atomic radius of potassium is \(235 \mathrm{pm}\). Determine (a) the number of atoms per unit cell; (b) the coordination number of the lattice; (c) the length of the side of the unit cell.