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Observation 3: temperature dependence of the reaction equilibrium

We have previously observed that phase equilibrium, and in particular vapor pressure, depend on thetemperature, but we have not yet studied the variation of reaction equilibrium with temperature. We focus our initial study on this reaction and we measure the equilibrium partial pressures at a variety of temperatures. From these measurements, we can compile the datashowing the temperature dependence of the equilibrium constant K p for this reaction in [link] .

Equilibrium constant for the synthesis of hi
T (K) K p
500 6.25 × 10 –3
550 8.81 × 10 –3
650 1.49 × 10 –2
700 1.84 × 10 –2
720 1.98 × 10 –2

Note that the equilibrium constant increases dramatically with temperature. As a result, at equilibrium, thepressure of HImust also increase dramatically as the temperature is increased.

These data do not seem to have a simple relationship between K p and temperature. We must appeal to arguments based on Thermodynamics, from which it is possible to show that theequilibrium constant should vary with temperature according to the following equation:

K p Δ H ° R T Δ S ° R

If Δ H ° and Δ S ° do not depend strongly on the temperature, then this equation would predict a simple straight line relationship between K p and 1 T . In addition, the slope of this line should be Δ H ° R . We test this possibility with the graph in [link] .

Inverse of temperature vs. natural log of equilibrium constant

In fact, we do observe a straight line through the data. In this case, the line has a negative slope. Notecarefully that this means that K p is increasing with temperature. The negative slope via [link] means that Δ H ° R must be negative, and indeed for this reaction in this temperature range, Δ H ° 15.6 kJ mol . This value matches well with the slope of the line in [link] .

Given the validity of [link] in describing the temperature dependence of the equilibrium constant, we can also predict that anexothermic reaction with Δ H ° 0 should have a positive slope in the graph of K p versus 1 T , and thus the equilibrium constant should decrease with increasing temperature. A good example of an exothermic reaction is the synthesis of ammonia for which Δ H ° -99.2 kJ mol . Equilibrium constant data are given in [link] . Note that, as predicted, the equilibrium constant for this exothermic reaction decreases rapidlywith increasing temperature. The data from [link] is shown in [link] , clearly showing the contrast between the endothermic reaction and the exothermic reaction. Theslope of the graph is positive for the exothermic reaction and negative for the endothermic reaction. From [link] , this is a general result for all reactions.

Equilibrium constant for the synthesis of ammonia
T (K) K p
250 7.8 × 10 8
298 6 × 10 5
350 2 × 10 3
400 36

Inverse of temperature vs. natural log of equilibrium constant

Observation 4: changes in equilibrium and le châtelier's principle

One of our goals at the outset was to determine whether it is possible to control the equilibrium whichoccurs during a gas reaction. We might want to force a reaction to produce as much of the products as possible. In the alternative, ifthere are unwanted by-products of a reaction, we might want conditions which minimize the product. We have observed that theamount of product varies with the quantities of initial materials and with changes in the temperature. Our goal is a systematicunderstanding of these variations.

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..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
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.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
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
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
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
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
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 2012. OpenStax CNX. Aug 16, 2012 Download for free at http://legacy.cnx.org/content/col11444/1.4
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