Video Transcript
A chemist is given three different
liquids and wants to determine which one is the most volatile. The chemist places an equal volume
of each liquid into a manometer and ensures the temperature of all three liquids is
the same. According to the image below, which
liquid is the most volatile? Ethylene glycol, propanol, or
diethyl ether.
The vapor pressure of a substance
is the pressure exerted by a vapor above its liquid when they are at dynamic
equilibrium. The vapor pressure of a substance
can be related to its volatility. The volatility of a liquid
indicates how readily it evaporates. The more volatile a substance is,
the greater its vapor pressure is at a given temperature. Therefore, a highly volatile liquid
will readily evaporate.
A manometer is a device that can be
used to measure the vapor pressure of a liquid. A manometer consists of a curved
glass tube which contains liquid mercury. At the other end of the manometer
is a spherical container, which is similar to a flask and holds the liquid
sample. Mercury is used because it has an
incredibly low vapor pressure. Its vapor pressure will have little
to no effect on the measurement of the vapor pressure of another liquid.
When a liquid sample is inside the
manometer, the mercury will be pushed inside the tube by the force of the vapor
pressure of the sample. The greater the height difference
between mercury levels on the left and right sides of the tube, the greater the
vapor pressure of the liquid sample. According to the image, diethyl
ether has the greatest vapor pressure because the difference in mercury levels is
the greatest.
Based on our discussion, we’ve
learned that this also means that diethyl ether is the most volatile liquid. In conclusion, according to the
image, the liquid that is the most volatile is diethyl ether.
