36. In each of the following groups of substances, pick the one that has the given property . Justify each answer. a. highest boiling point: CCl_(4),CF_(4),CBr_(4) b. lowest freezing point: LiF,F_(2),HCl c. smallest vapor pressure at 25^circ C:CH_(3)OCH_(3),CH_(3)CH_(2)OH CH_(3)CH_(2)CH_(3) d. greatest viscosity: H_(2)S,HF,H_(2)O_(2)

a. The boiling point of a substance is determined by the strength of the intermolecular forces between its molecules. In this case, the boiling point of $CBr_{4}$ is the highest because bromine atoms are larger and more polarizable than chlorine atoms in $CCl_{4}$ and fluorine atoms in $CF_{4}$. This results in stronger London dispersion forces in $CBr_{4}$, leading to a higher boiling point.<br /><br />b. The freezing point of a substance is also determined by the strength of the intermolecular forces between its molecules. In this case, $F_{2}$ has the lowest freezing point because it has the weakest intermolecular forces among the given substances. Fluorine atoms in $F_{2}$ are nonpolar and have weak van der Waals forces, resulting in a lower freezing point compared to $LiF$ and $HCl$.<br /><br />c. Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid or solid phase. The vapor pressure of a substance is inversely proportional to the strength of the intermolecular forces between its molecules. In this case, $CH_{3}CH_{2}CH_{3}$ has the smallest vapor pressure at $25^{\circ }C$ because it has the weakest intermolecular forces among the given substances. The molecules in $CH_{3}CH_{2}CH_{3}$ are nonpolar and have weak van der Waals forces, resulting in a lower vapor pressure compared to $CH_{3}OCH_{3}$ and $CH_{3}CH_{2}OH$.<br /><br />d. Viscosity is a measure of a fluid's resistance to flow. The viscosity of a substance is directly proportional to the strength of the intermolecular forces between its molecules. In this case, $H_{2}O_{2}$ has the greatest viscosity because it has the strongest intermolecular forces among the given substances. The molecules in $H_{2}O_{2}$ are polar and have strong hydrogen bonding, resulting in a higher viscosity compared to $H_{2}S$ and $HF$.