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In Figure 2, we can now more easily see that, when the density of the gas gets high enough, the Ideal Gas Law is no longer accurate. In addition, the amount by which the Ideal Gas Law is incorrect, which we might call the “deviation” from the Ideal Gas Law, is different for each gas at high density.

If we push the density of each gas to much higher values, this deviation becomes much greater. This is shown in Figure 3 for N 2 . There are two types of deviation of Figure 3 worth studying. As we start at low density and then increase the density, the value of PV/nRT drops below 1. Note that, just as in Figure 1,the pressure of the gas continues to increase but it increase less than the pressure predicted by the Ideal Gas Law. This is true of most gases and is called “negative deviation” from the Ideal Gas Law, since the pressure is not as great as expected. If we continue to increase the density of the gas, PV/nRT rises about 1, so the pressure of the gas becomes greater than the pressure predicted by the Ideal Gas Law. This is called “positive deviation” from the Ideal Gas Law. The extent of negative deviation or positive deviation is different for different gases, and the pressures at which these deviations occur differ as well, but the graph for N 2 is fairly typical in shape.

We looked at these data to find the limits of the validity of the Ideal Gas Law. From these data, we can definitely conclude that the Ideal Gas Law works quite well provided that the density of the gas n/V is not too high. This is a very valuable conclusion but we need additional data before we can build a model for why this is true.

Observation 2: densities of gases and liquids

In Figures 1 and 2, we looked at gas densities where the Ideal Gas Law is accurate. Even at what we might call “high density” in Figures 1 and 2, the density is very low if we compare it to the density of a liquid. In fact, the differences between liquids and gases are enormous. To see this, let’s look at 1.0 g of H 2 O. The volume of 1.0 g of liquid water is very close to 1.0 mL. It varies somewhat with changing temperature, but not very much at all, and even just below the boiling point of water, the volume of 1.0 g of H 2 O is close to 1.0 mL.

Now let’s boil that 1.0 g of liquid H 2 O and let’s figure out what volume the H 2 O gas can fill. From the Ideal Gas Law, we know that the volume is related to the pressure, so let’s take the pressure to be standard pressure, 1 atm. At 100 ↓C and 1 atm pressure, 1.0 g of water gas has a volume of 1700 mL. This means that the same molecules occupy a space which is 1700 times greater when they are in a gas instead of a liquid. This is a very large increase.

How can the molecules occupy so much more space? Perhaps the molecules increase in size by a factor of 1700 when they are gas molecules instead of liquid molecules. But this sounds strange and doesn’t fit other experimental data. The volume of the gas varies with the pressure, so the value 1700 is only valid for a pressure of 1 atm. If we take a lower pressure, the volume increases, and if we take a higher pressure, the volume decreases. It seems unlikely the molecules can change their sizes to fit the pressure. If we try the same changes in pressure for the liquid, we discover that the volume of the liquid changes by such a tiny amount that it is only observable with very careful measurements. If molecules change size with pressure changes, the volume of the liquid should change too. But it does not. We have to conclude that the huge differences in the volumes of a liquid and a gas are not a result of molecules changing size when they evaporate.

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
yes that's correct
I think
Nasa has use it in the 60's, copper as water purification in the moon travel.
nanocopper obvius
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
analytical skills graphene is prepared to kill any type viruses .
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Concept development studies in chemistry 2013. OpenStax CNX. Oct 07, 2013 Download for free at http://legacy.cnx.org/content/col11579/1.1
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