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It is important to note that we can vary the relative amount ofNH 3 produced by varying the temperature of the reaction, the volume of the vessel in which the reaction occurs, or the relative startingamounts of N 2 and H 2 . We shall study and analyze this observation in detail in latersections. For now, though, we demonstrate that the concept of reaction equilibrium is general to all reactions.

Consider the reaction

H 2 ( g ) + I 2 ( g ) 2 H I ( g )

If we begin with 1.00 mole of H 2 and 1.00 mole of i 2 at 500 K in a reaction vessel of fixed volume, we observe that, at equilibrium, n H I 1.72 mol , leaving in the equilibrium mixture n H 2 0.14 mol and n I 2 0.14 mol .

Similarly, consider the decomposition reaction

N 2 O 4 ( g ) 2 N O 2 ( g )

At 298K in a 100.0L reaction flask, 1.00 mol ofN 2 O 4 partially decomposes to produce, at equilibrium, n N O 2 0.64 mol and n N 2 O 4 0.68 mol .

Some chemical reactions achieve an equilibrium that appears to be very nearly complete reaction. Forexample,

H 2 ( g ) + Cl 2 ( g ) 2 H Cl ( g )

If we begin with 1.00 mole of H 2 and 1.00 mole of Cl 2 at 298K in a reaction vessel of fixed volume, we observe that, at equilibrium, n H Cl is almost exactly 2.00 mol, leaving virtually no H 2 or Cl 2 This does not mean that the reaction has not come to equilibrium. It means instead that, at equilibrium, there are essentially noreactants remaining.

In each of these cases, the amounts of reactants and products present at equilibrium vary as theconditions are varied but are completely reproducible for fixed conditions. Before making further observations that will lead to aquantitative description of the reaction equilibrium, we consider a qualitative description of equilibrium.

We begin with a dynamic equilibrium description. We know from our studies of phase transitions thatequilibrium occurs when the rate of the forward process ( e.g. evaporation) is matched by the rate of reverse process ( e.g. condensation). Since we have now observed that gas reactions also come to equilibrium, we postulate that at equilibrium the forwardreaction rate is equal to the reverse reaction rate. For example, in the reaction here , the rate of decomposition ofN 2 O 4 molecules at equilibrium must be exactly matched by the rate ofrecombination (or dimerization ) of NO 2 molecules.

To show that the forward and reverse reactions continue to happen at equilibrium, we start with theNO 2 and N 2 O 4 mixture at equilibrium and we vary the volume of the flask containing the mixture. We observe that, if we increase the volumeand the reaction is allowed to come to equilibrium, the amount of NO 2 at equilibrium is larger at the expense of a smaller amount of N 2 O 4 . We can certainly conclude that the amounts of the gases atequilibrium depend on the reaction conditions. However, if the forward and reverse reactions stop once the equilibrium amounts ofmaterial are achieved, the molecules would not "know" that the volume of the container had increased. Since the reactionequilibrium can and does respond to a change in volume, it must be that the change in volume affects the rates of both the forward andreverse processes. This means that both reactions must be occurring at equilibrium, and that their rates must exactly match atequilibrium.

Questions & Answers

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.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
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
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
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?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
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
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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
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