Raunak need help to clarify doubt about: : Why do some drops of mercury vaporise in the Torricellian Vacuum of a simple mercury barometer?
I have been taught that some drops of mercury often vaporise in the Torricellian vacuum but do not change the barometric height as the vapor pressure of mercury is negligible. Please explain me all this.
Try this:
Answer by Civil
All liquids will lose a few molecules from their surface into the surrounding medium, simply by virtue of statistics, because there
will always be a few molecules with a slightly higher kinetic energy
than the average (just as there are a few with lower than average
kinetic energy). So even for a liquid with an
extremely low vapor pressure like mercury, there are a few atoms
that have enough energy to leave the liquid surface. And, if the surrounding medium happens to be a vacuum, then the
vaporization process is maximized because the liquid is not competing
with the air by trading atoms back and forth.
The reason that the barometric height is not affected, however, is because we are only talking about a relatively few atoms of mercury contained in that
vacuum. The number is below the amount that would be needed to
produce a noticeable change in the reading on the barometer.
Give your answer to this question below!