# 0.18 Reaction equilibrium in the gas phase  (Page 7/6)

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## Foundation

In beginning our study of the reactions of gases, we will assume a knowledge of the physical properties ofgases as described by the Ideal Gas Law and an understanding of these properties as given by the postulates and conclusions of the Kinetic Molecular Theory . We assume that we have developed a dynamic model of phase equilibrium in terms of competing rates. We willalso assume an understanding of the bonding, structure, and properties of individual molecules.

## Goals

In performing stoichiometric calculations, we assume that we can calculate the amount of product of a reactionfrom the amount of the reactants we start with. For example, if we burn methane gas,CH 4 (g), in excess oxygen, the reaction

$\text{C}{\text{H}}_{4}\left(g\right)+2{\text{O}}_{2}\left(g\right)\to \text{C}{\text{O}}_{2}\left(g\right)+2{\text{H}}_{2}\text{O}\left(g\right)$

occurs, and the number of moles of CO 2 (g) produced is assumed to equal the number of moles ofCH 4 (g) we start with.

From our study of phase transitions we have learned the concept of equilibrium. We observed that, in thetransition from one phase to another for a substance, under certain conditions both phases are found to coexist, and we refer to thisas phase equilibrium. It should not surprise us that these same concepts of equilibrium apply to chemical reactions as well. In the reaction , therefore, we should examine whether the reaction actually producesexactly one mole of CO 2 for every mole ofCH 4 we start with or whether we wind up with an equilibrium mixture containing bothCO 2 and CH 4 . We will find that different reactions provide us with varyinganswers. In many cases, virtually all reactants are consumed, producing the stoichiometric amount of product. However, in manyother cases, substantial amounts of reactant are still present when the reaction achieves equilibrium, and in other cases, almost noproduct is produced at equilibrium. Our goal will be to understand, describe and predict the reaction equilibrium.

An important corollary to this goal is to attempt to control the equilibrium. We will find that varying theconditions under which the reaction occurs can vary the amounts of reactants and products present at equilibrium. We will develop ageneral principle for predicting how the reaction conditions affect the amount of product produced at equilibrium.

## Observation 1: reaction equilibrium

We begin by analyzing a significant industrial chemical process, the synthesis of ammonia gas,NH 3 , from nitrogen and hydrogen:

${\text{N}}_{2}\left(g\right)+3{\text{H}}_{2}\left(g\right)\to 2\text{N}{\text{H}}_{3}\left(g\right)$

If we start with 1 mole of N 2 and 3 moles of H 2 , the balanced equation predicts that we will produce 2 moles ofNH 3 . In fact, if we carry out this reaction starting with thesequantities of nitrogen and hydrogen at 298 K in a 100.0 L reaction vessel, we observe that the number of moles ofNH 3 produced is 1.91 mol. This "yield" is less than predicted by the balanced equation, but the difference is not dueto a limiting reagent factor. Recall that, in stoichiometry, the limiting reagent is the one that is present in less than the ratioof moles given by the balanced equation. In this case, neither N 2 nor H 2 is limiting because they are present initially in a 1:3 ratio, exactly matching the stoichiometry. Note also that this seemingdeficit in the yield is not due to any experimental error or imperfection, nor is it due to poor measurements or preparation.Rather, the observation that, at 298 K, 1.91 moles rather than 2moles are produced is completely reproducible: every measurement of this reaction at this temperature in this volume starting with 1mole of N 2 and 3 moles of H 2 gives this result. We conclude that the reaction achieves reaction equilibrium in which all three gases are present in the gas mixture. We can determine the amountsof each gas at equilibrium from the stoichiometry of the reaction. When ${n}_{N{H}_{3}}=1.91\phantom{\rule{0.25em}{0ex}}\mathrm{mol}$ are created, the number of moles of N 2 remaining at equilibrium is ${n}_{{N}_{2}}=0.045\phantom{\rule{0.25em}{0ex}}\mathrm{mol}$ and ${n}_{{H}_{2}}=0.135\phantom{\rule{0.25em}{0ex}}\mathrm{mol}$ .

#### Questions & Answers

what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
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Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
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.
Bharti
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
Daniel
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Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
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Anassong
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
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
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.
Tarell
what is the actual application of fullerenes nowadays?
Damian
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.
Tarell
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.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
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.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
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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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