81. In Breckenridge, Colorado, the typical atmospheric pressure is
520. torr. What is the boiling point of water \( \left(\Delta H_{\text {vap }}=40.7\right. \) \( \mathrm{kJ} / \mathrm{mol} \), in Breckenridge?
82. What pressure would have to be applied to steam at \( 350 .^{\circ} \mathrm{C} \) to condense the steam to liquid water \( \left(\Delta H_{\text {vap }}=40.7 \mathrm{~kJ} / \mathrm{mol}\right) \) ?
83. Carbon tetrachloride, \( \mathrm{CCl}_{4} \), has a vapor pressure of 213 torr at \( 40 .{ }^{\circ} \mathrm{C} \) and 836 torr at \( 80 .{ }^{\circ} \mathrm{C} \). What is the normal boiling point of \( \mathrm{CCl}_{4} \) ?
84. The normal boiling point for acetone is \( 56.5^{\circ} \mathrm{C} \). At an elevation of \( 5300 \mathrm{ft} \) the atmospheric pressure is 630 . torr. What would be the boiling point of acetone \( \left(\Delta H_{\text {vap }}=32.0 \mathrm{~kJ} / \mathrm{mol}\right. \) ) at this elevation? What would be the vapor pressure of acetone at \( 25.0^{\circ} \mathrm{C} \) at this elevation?
85. A substance, \( X \), has the following properties:
\begin{tabular}{lccc}
& & \multicolumn{2}{c} { Specific Heat Capacities } \\
\hline\( \Delta H_{\text {vap }} \) & \( 20 . \mathrm{kJ} / \mathrm{mol} \) & \( \mathrm{C}(s) \) & \( 3.0 \mathrm{~J} / \mathrm{g} \cdot{ }^{\circ} \mathrm{C} \) \\
\( \Delta H_{\text {fus }} \) & \( 5.0 \mathrm{~kJ} / \mathrm{mol} \) & \( \mathrm{C}(l) \) & \( 2.5 \mathrm{~J} / \mathrm{g} \cdot{ }^{\circ} \mathrm{C} \) \\
\( \mathrm{bp} \) & \( 75^{\circ} \mathrm{C} \) & \( \mathrm{C}(g) \) & \( 1.0 \mathrm{~J} / \mathrm{g} \cdot{ }^{\circ} \mathrm{C} \) \\
\( \mathrm{mp} \) & \( -15^{\circ} \mathrm{C} \) & &
\end{tabular}
Sketch a heating curve for substance \( X \) starting at \( -50 .{ }^{\circ} \mathrm{C} \).
86. Given the data in Exercise 85 on substance \( X \), calculate the enbrov that must he removed to convert \( 250 . \mathrm{g} \) of substance \( \mathrm{X} \) from
