# 1.2 Introduction to combustion analysis  (Page 4/4)

 Page 4 / 4

Generally, the following reaction takes place in combustion analysis:

After burning 1.333 g of a hydrocarbon in a combustion analysis apparatus, 1.410 g of H 2 O and 4.305 g of CO 2 were produced. Separately, the molar mass of this hydrocarbon was found to be 204.35 g/mol. Calculate the empirical and molecular formulas of this hydrocarbon.

Step 1 : Using the molar masses of water and carbon dioxide, determine the moles of hydrogen and carbon that were produced.

Step 2 : Divide the larger molar amount by the smaller molar amount. In some cases, the ratio is not made up of two integers. Convert the numerator of the ratio to an improper fraction and rewrite the ratio in whole numbers as shown.

Therefore, the empirical formula is C 5 H 8 .

Step 3 : To get the molecular formula, divide the experimental molar mass of the unknown hydrocarbon by the empirical formula weight.

Therefore, the molecular formula is (C 5 H 8 ) 3 or C 15 H 24 .

After burning 1.082 g of a hydrocarbon in a combustion analysis apparatus, 1.583 g of H 2 O and 3.315 g of CO 2 were produced. Separately, the molar mass of this hydrocarbon was found to be 258.52 g/mol. Calculate the empirical and molecular formulas of this hydrocarbon.

The empirical formula is C 3 H 7 , and the molecular formula is (C 3 H 7 ) 6 or C 18 H 42 .

## Compounds containing carbon, hydrogen, and oxygen

Combustion analysis can also be utilized to determine the empiric and molecular formulas of compounds containing carbon, hydrogen, and oxygen. However, as the reaction is performed in an environment of excess oxygen, the amount of oxygen in the sample can be determined from the sample mass, rather than the combustion data ( [link] , [link] ).

A 2.0714 g sample containing carbon, hydrogen, and oxygen was burned in a combustion analysis apparatus; 1.928 g of H 2 O and 4.709 g of CO 2 were produced. Separately, the molar mass of the sample was found to be 116.16 g/mol. Determine the empirical formula, molecular formula, and identity of the sample.

Step 1 : Using the molar masses of water and carbon dioxide, determine the moles of hydrogen and carbon that were produced.

Step 2 : Using the molar amounts of carbon and hydrogen, calculate the masses of each in the original sample.

Step 3 : Subtract the masses of carbon and hydrogen from the sample mass. Now that the mass of oxygen is known, use this to calculate the molar amount of oxygen in the sample.

Step 4 : Divide each molar amount by the smallest molar amount in order to determine the ratio between the three elements.

Therefore, the empirical formula is C 3 H 6 O.

Step 5 : To get the molecular formula, divide the experimental molar mass of the unknown hydrocarbon by the empirical formula weight.

Therefore, the molecular formula is (C 3 H 6 O) 2 or C 6 H 12 O 2 . Possible compound with this molecular formula are shown in ( [link] ).

A 4.846 g sample containing carbon, hydrogen, and oxygen was burned in a combustion analysis apparatus; 4.843 g of H 2 O and 11.83 g of CO 2 were produced. Separately, the molar mass of the sample was found to be 144.22 g/mol. Determine the empirical formula, molecular formula, and identity of the sample.

The empirical formula is C 4 H 8 O, and the molecular formula is (C 4 H 8 O) 2 or C 8 H 16 O 2 . Possible compounds with this molecular formula are shown in ( [link] ).

## Binary compounds

By using combustion analysis, the chemical formula of a binary compound containing oxygen can also be determined. This is particularly helpful in the case of combustion of a metal which can result in potential oxides of multiple oxidation states.

A sample of iron weighing 1.7480 g is combusted in the presence of excess oxygen. A metal oxide (Fe x O y ) is formed with a mass of 2.4982 g. Determine the chemical formula of the oxide product and the oxidation state of Fe.

Step 1 : Subtract the mass of Fe from the mass of the oxide to determine the mass of oxygen in the product.

Step 2 : Using the molar masses of Fe and O, calculate the molar amounts of each element.

Step 3 : Divide the larger molar amount by the smaller molar amount. In some cases, the ratio is not made up of two integers. Convert the numerator of the ratio to an improper fraction and rewrite the ratio in whole numbers as shown.

Therefore, the chemical formula of the oxide is Fe 2 O 3 , and Fe has a 3+ oxidation state.

A sample of copper weighing 7.295 g is combusted in the presence of excess oxygen. A metal oxide (Cu x O y ) is formed with a mass of 8.2131 g. Determine the chemical formula of the oxide product and the oxidation state of Cu.

The chemical formula is Cu 2 O, and Cu has a 1+ oxidation state.

## Bibliography

• J. A. Dumas, Ann. Chem. Pharm. , 1841, 38 , 141.
• H. Goldwhite, J. Chem. Edu. , 1978, 55 , 366.
• A. Lavoisier, Traité Élémentaire de Chimie , 1789, 2 , 493.
• J. Von Liebig, Annalen der Physik und Chemie , 1831, 21 , 1.
• A. Linan and F. A. Williams, Fundamental Aspects of Combustion , Oxford University Press, New York (1993).
• J. M. McBride, "Combustion Analysis," Chemistry 125 , Yale University,<http://www.chem.yale.edu/~chem125/125/history99/4RadicalsTypes/Analysis/Liebiganal.html>.
• W. Prout, Philos. T. R. Soc. Lond. , 1827, 117 , 355.
• D. Shriver and P. Atkins, Inorganic Chemistry , 5 th Ed., W. H. Freeman and Co., New York (2009).
• W. Vining et. al., General Chemistry , 1 st Ed., Cengage, Brooks/Cole Cengage Learning , University of Massachusetts Amherst (2014).
• J. Warnatz, U. Maas, and R. W. Dibble, Combustion: Physical and Chemical Fundamentals, Modeling and Simulation, Experiments, Pollutant Formation , 3 rd Ed., Springer, Berlin (2001).

do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
it is a goid question and i want to know the answer as well
Maciej
Abigail
Do somebody tell me a best nano engineering book for beginners?
what is fullerene does it is used to make bukky balls
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
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
so some one know about replacing silicon atom with phosphorous in semiconductors device?
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 ?
for screen printed electrodes ?
SUYASH
What is lattice structure?
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
what's the easiest and fastest way to the synthesize AgNP?
China
Cied
types of nano material
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
what is nano technology
what is system testing?
preparation of nanomaterial
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
what is system testing
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
how did you get the value of 2000N.What calculations are needed to arrive at it
Privacy Information Security Software Version 1.1a
Good
Berger describes sociologists as concerned with
how I can reaction of mercury?