<< Chapter < Page Chapter >> Page >

Note that, in varying either the amount of liquid initially or the fixed volume of the container, the amount of liquid water that evaporates must be different in each case. This can be seen fromthe fact that the volume available for vapor must be different in varying either the volume of the container or the initial volume ofthe liquid. Since we observe that the pressure of the vapor is the same at a fixed temperature, the differing volumes reveal differingnumbers of moles of water vapor. Clearly it is the pressure of the vapor, not the amount, which is the most important property in establishing theequilibrium between the liquid and the vapor. We can conclude that, at a given fixed temperature, there is a single specific pressureat which a given liquid and its vapor will be in phase equilibrium. We call this the vapor pressure of the liquid.

We can immediately observe some important features of the vapor pressure. First, for a given substance, thevapor pressure varies with the temperature. This can be found by simply increasing the temperature on the closed container in thepreceding experiment. In every case, we observe that the equilibrium vapor pressure increases with increases in the temperature.

The vapor pressures of several liquids at several temperatures are shown here . The vapor pressure for each liquid increases smoothly with the temperature, althoughthe relationship between vapor pressure and temperature is definitely not proportional.

Vapor pressures of various liquids

Second, [link] clearly illustrates that the vapor pressure depends strongly on what the liquid substance is. Thesevariations reflect the differing volatilities of the liquids: those with higher vapor pressures are more volatile. In addition, there is avery interesting correlation between the volatility of a liquid and the boiling point of the liquid. Without exception, the substanceswith high boiling points have low vapor pressures and vice versa.

Looking more closely at the connection between boiling point and vapor pressure, we can find an importantrelationship. Looking at [link] , we discover that the vapor pressure of each liquid is equal to 760torr (which is equal to 1 atm) at the boiling point for that liquid. How should we interpret this? At an applied pressure of 1atm, the temperature of the phase transition from liquid to gas is the temperature at which the vapor pressure of the liquid is equalto 1 atm. This statement is actually true regardless of which pressure we consider: if we apply a pressure of 0.9 atm, theboiling point temperature is the temperature at which the liquid as a vapor pressure of 0.9 atm. Stated generally, the liquid undergoesphase transition at the temperature where the vapor pressure equals the applied pressure.

Observation 3: phase diagrams

Since the boiling point is the temperature at which the applied pressure equals the vapor pressure, then we canview [link] in a different way. Consider the specific case of water, with vapor pressure given here . To find the boiling point temperature at 1 atm pressure, we need to findthe temperature at which the vapor pressure is 1 atm. To do so, we find the point on the graph where the vapor pressure is 1 atm andread off the corresponding temperature, which must be the boiling point. This will work at any given pressure. Viewed this way, forwater [link] gives us both the vapor pressure as a function of the temperature and the boiling point temperature as a function of the pressure. They are the same graph.

Questions & Answers

how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
can nanotechnology change the direction of the face of the world
Prasenjit Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Got questions? Join the online conversation and get instant answers!
QuizOver.com Reply

Get the best Algebra and trigonometry course in your pocket!

Source:  OpenStax, Concept development studies in chemistry 2012. OpenStax CNX. Aug 16, 2012 Download for free at http://legacy.cnx.org/content/col11444/1.4
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Concept development studies in chemistry 2012' conversation and receive update notifications?