Eileen Sullivan, Head of Science Department at The Hotchkiss School, Numerade Educator

04:02

Chemistry Principles and Reactions

1. Methyl alcohol can be used as a fuel instead of, or combined with, gasoline. A sample of methyl alcohol, $\mathrm{CH}_{3} \mathrm{OH}$, in a flask of constant volume exerts a pressure of $254 \mathrm{~mm} \mathrm{Hg}$ at $57^{\circ} \mathrm{C}$. The flask is slowly cooled.
(a) Assuming no condensation, use the ideal gas law to calculate the pressure of the vapor at $35^{\circ} \mathrm{C} ;$ at $45^{\circ} \mathrm{C}$.
(b) Compare your answers in (a) with the equilibrium vapor pressures of methyl alcohol: $203 \mathrm{~mm} \mathrm{Hg}$ at $35^{\circ} \mathrm{C}$; $325 \mathrm{~mm} \mathrm{Hg}$ at $45^{\circ} \mathrm{C}$
(c) On the basis of your answers to (a) and (b), predict the pressure exerted by the methyl alcohol in the flask at $35^{\circ} \mathrm{C} ;$ at $45^{\circ} \mathrm{C}$
(d) What physical states of methyl alcohol are present in the flask at $35^{\circ} \mathrm{C}$ ? at $45^{\circ} \mathrm{C} ?$

Chapter 9: Liquids and Solids