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Application of mole concept requires a balanced chemical equation. The different constituents of the reaction – reactants and products – bear a simple whole number proportion same as the proportion of the coefficients associated with constituents. According to mole concept, the molar mass of constituents participates in this proportion. For a generic consideration as given :

x A + y B A x B y

Here, 1 mole of compound ( A x B y ) involves x mole of A and y mole of B. Using symbols :

x moles of A y moles of B 1 mole of A x B y

The point to emphasize here is that this is a relation, which is connected by "equivalence sign (≡)" - not by "equal to (=)" sign. We know that 2 moles of hydrogen reacts with 1 mole of oxygen to form 2 moles of water. Clearly, we can not equate like 2=1=2. We need to apply unitary method to interpret this relation of equivalence. We say that since x moles of A react with y moles of B. Hence, 1 mole of A reacts with y/x moles of "B". Similarly, 1 mole of B reacts with x/y moles of "A". Once we know the correspondence for 1 mole, we can find correspondence for any other value of participating moles of either A or B.

Mass of participating entities in a reaction

Mole concept is used to calculate mass of individual constituent of a chemical reaction. The proportion of molar mass is converted to determine proportion of mass in which entities are involved in a reaction. The symbolic mass relation for the chemical reaction as given above is :

x M A gm of A y M B gm of B M A x B y gm of A x B y

We apply unitary method on the mass relation related with equivalent sign (≡) to determine mass of different entities of the reaction.

Problem : Calculate mass of lime (CaO) that can be prepared by heating 500 kg of 90 % pure limestone ( C a C O 3 .

Solution : Purity of CaCO3 is 90 %. Hence,

Mass of C a C O 3 = 0.9 X 500 = 450 k g

The chemical reaction involved here is :

C a C O 3 C a O + C O 2

Applying mole concept :

1 mole of C a C O 3 1 mole of CaO

(40 + 12 + 3X 16) gm of C a C O 3 (40 + 16) gm of CaO

100 gm of C a C O 3 56 gm of CaO

100 kg of C a C O 3 56 kg of CaO

Applying unitary method :

mass of CaO produced = 56 X 450 100 = 252 k g

Problem : Igniting M n O 2 converts it quantitatively to M n 3 O 4 . A sample of pyrolusite contains 80% M n O 2 , 15 % S i O 2 and 5 % water. The sample is ignited in air to constant weight. What is the percentage of manganese in the ignited sample ? ( A M n = 55 )

Solution : The sample contains three components. Since this question involves percentage, we shall consider a sample of 100 gm. Water component weighing 5 gm evaporates on ignition. S i O 2 weighing 15 gm does not change. On the other hand, 80 gm of M n O 2 converts as :

3 M n O 2 M n 3 O 4 + O 2

Applying mole concept,

3 moles of M n O 2 1 mole of M n 3 O 4

3 X 55 + 2 X 16 gm of M n O 2 1 X 3 X 55 + 4 X 16 gm of M n 3 O 4

261 gm of M n O 2 229 gm of M n 3 O 4

Since sample is ignited in air to constant weight, it means that all of Mn O 2 in the sample is converted. Using unitary method, we determine mass of converted mass of M n 3 O 4 for 80 gm of Mn O 2 :

Mass of M n 3 O 4 on conversion = 229 261 X 80 = 70.2 g m

We are required to find the percentage of Mn in the ignited sample. Thus, we need to determine the mass of the ignited sample. The ignited sample contains 70.2 gm of M n 3 O 4 and 15 gm of S i O 2 . Total mass of ignited sample is 70.2+15 = 85.4 gm. On the other hand, amount of Mn in M n 3 O 4 is calculated from its molecular constitution :

229 gm of M n 3 O 4 3 X 55 gm of Mn 165 gm of Mn

Amount of Mn in 70.2 gm of M n 3 O 4 = 165 229 X 70.2 = 0.72 X 70.2 = 50.54 g m

Clearly, 85.4 gm of ignited sample contains 50.54 gm of Mn. Hence,

Percentage amount of manganese in the ignited sample = 50.54 85.4 X 100 = 59.2 %

Questions & Answers

How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
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.
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
How can I make nanorobot?
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
how can I make nanorobot?
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
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Source:  OpenStax, Stoichiometry. OpenStax CNX. Jul 05, 2008 Download for free at http://cnx.org/content/col10540/1.7
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