# This graph shows how the vapor pressure of three liquids varies with temperature:

This graph shows how the vapor pressure of three liquids varies with temperature:

Volatility of a liquid is a measure of the tendency of its molecules to escape in the vapor phase. Thus, the compound that has a higher vapor pressure at a given temperature is more volatile, Or in other words, the compound that achieves a particular vapor pressure at the lower temperature is more volatile.

Part A. Among the given compounds, the given marked vapor pressure is achieved at the lowest temperature by octane and at the highest temperature by orthoxylene. Thus, the most volatile compound is octane, and the least volatile compound is orthoxylene.

Part B. The normal boiling point is that temperature at which the vapor pressure of the liquid is 1 atm or 760 torr.

The least count for the \mathrm{x} -axis is 1 \mathrm{C}, that is 1 unit =10^{\circ} \mathrm{C}. The least count for the \mathrm{y} -axis is 20 torr, that is 1 unit =100 torr.

Consider the graph given below:

From the above graph it can be seen that,

The normal boiling point of octane is 121 \mathrm{C}.

The normal boiling point of acetylacetone is 133{ }^{\circ} \mathrm{C}.

The normal boiling point of orthoxylene is 139 \mathrm{CC}.

Part C. The vapor pressure of octane at 112^{\circ} \mathrm{C} is 500 torr. Thus, when octane is placed in a beaker in a sealed tank at 112^{\prime} \mathrm{C} and 281 torr, it will vaporize until the pressure becomes equal to 500 torr. Therefore, after 10 minutes there will less liquid in the beaker.

### Raymond Puzio

Raymond Puzio has a PhD in Physics from Yale University. I have been creating PlanetPhysics with Aaron Krowne and Ben Loftin since 2005.