# 15.1 Stoichiometry and composition  (Page 4/5)

 Page 4 / 5

What volume of oxygen at S.T.P. is needed for the complete combustion of $2\phantom{\rule{2pt}{0ex}}{\mathrm{dm}}^{3}$ of propane ( $\mathrm{C}{}_{3}\mathrm{H}{}_{8}$ )? (Hint: $\mathrm{CO}{}_{2}$ and $\mathrm{H}{}_{2}\mathrm{O}$ are the products in this reaction (and in all combustion reactions))

1. ${\mathrm{C}}_{3}{\mathrm{H}}_{8}\left(\mathrm{g}\right)+5{\mathrm{O}}_{2}\left(\mathrm{g}\right)\to 3\mathrm{C}{\mathrm{O}}_{2}\left(\mathrm{g}\right)+4{\mathrm{H}}_{2}\mathrm{O}\left(\mathrm{g}\right)$

2. From the balanced equation, the ratio of oxygen to propane in the reactants is 5:1.

3. 1 volume of propane needs 5 volumes of oxygen, therefore $2\phantom{\rule{2pt}{0ex}}{\mathrm{dm}}^{3}$ of propane will need $10\phantom{\rule{2pt}{0ex}}{\mathrm{dm}}^{3}$ of oxygen for the reaction to proceed to completion.

What mass of iron (II) sulphide is formed when $5,6\phantom{\rule{2pt}{0ex}}\mathrm{g}$ of iron is completely reacted with sulphur?

1. $\mathrm{Fe}\left(\mathrm{s}\right)+\mathrm{S}\left(\mathrm{s}\right)\to \mathrm{FeS}\left(\mathrm{s}\right)$

2. $n=\frac{m}{M}=\frac{5,6}{55,85}=0,1\mathrm{mol}$
3. From the equation $1\phantom{\rule{2pt}{0ex}}\mathrm{mole}$ of $\mathrm{Fe}$ gives $1\phantom{\rule{2pt}{0ex}}\mathrm{mole}$ of $\mathrm{FeS}$ . Therefore, $0,1\phantom{\rule{2pt}{0ex}}\mathrm{moles}$ of iron in the reactants will give $0,1\phantom{\rule{2pt}{0ex}}\mathrm{moles}$ of iron sulphide in the product.

4. $m=n×M=0,1×87,911=8,79\phantom{\rule{2pt}{0ex}}\mathrm{g}$

The mass of iron (II) sulphide that is produced during this reaction is $8,79\phantom{\rule{2pt}{0ex}}\mathrm{g}$ .

When we are given a known mass of a reactant and are asked to work out how much product is formed, we are working out the theoretical yield of the reaction. In the laboratory chemists never get this amount of product. In each step of a reaction a small amount of product and reactants is 'lost' either because a reactant did not completely react or some of the product was left behind in the original container. Think about this. When you make your lunch or supper, you might be a bit hungry, so you eat some of the food that you are preparing. So instead of getting the full amount of food out (theoretical yield) that you started preparing, you lose some along the way.

Sulphuric acid ( $\mathrm{H}{}_{2}\mathrm{SO}{}_{4}$ ) reacts with ammonia ( $\mathrm{NH}{}_{3}$ ) to produce the fertiliser ammonium sulphate (( $\mathrm{NH}{}_{4}$ ) ${}_{2}\mathrm{SO}{}_{4}$ ) according to the following equation:

${\mathrm{H}}_{2}{\mathrm{SO}}_{4}\left(\mathrm{aq}\right)+2{\mathrm{NH}}_{3}\left(g\right)\to {\left({\mathrm{NH}}_{4}\right)}_{2}{\mathrm{SO}}_{4}\left(\mathrm{aq}\right)$

What is the maximum mass of ammonium sulphate that can be obtained from $2,0\phantom{\rule{2pt}{0ex}}\mathrm{kg}$ of sulphuric acid?

1. $n\left({\mathrm{H}}_{2}{\mathrm{SO}}_{4}\right)=\frac{m}{M}=\frac{2 000\phantom{\rule{2pt}{0ex}}\mathrm{g}}{98,078\phantom{\rule{2pt}{0ex}}\mathrm{g}·{\mathrm{mols}}^{-1}}=20,39\phantom{\rule{2pt}{0ex}}\mathrm{mols}$
2. From the balanced equation, the mole ratio of $\mathrm{H}{}_{2}\mathrm{SO}{}_{4}$ in the reactants to $\left(\mathrm{NH}{}_{4}\right){}_{2}\mathrm{SO}{}_{4}$ in the product is 1:1. Therefore, $20,39\phantom{\rule{2pt}{0ex}}\mathrm{mols}$ of $\mathrm{H}{}_{2}\mathrm{SO}{}_{4}$ of $\left(\mathrm{NH}{}_{4}\right){}_{2}\mathrm{SO}{}_{4}$ .

The maximum mass of ammonium sulphate that can be produced is calculated as follows:

$m=n×M=20,41\mathrm{mol}×132\phantom{\rule{2pt}{0ex}}\mathrm{g}·{\mathrm{mol}}^{-1}=2694\phantom{\rule{2pt}{0ex}}\mathrm{g}$

The maximum amount of ammonium sulphate that can be produced is $2,694\phantom{\rule{2pt}{0ex}}\mathrm{kg}$ .

## Stoichiometry

1. Diborane, $\mathrm{B}{}_{2}\mathrm{H}{}_{6}$ , was once considered for use as a rocket fuel. The combustion reaction for diborane is: ${\mathrm{B}}_{2}{\mathrm{H}}_{6}\left(\mathrm{g}\right)+3{\mathrm{O}}_{2}\left(\mathrm{g}\right)\to 2\mathrm{H}\mathrm{B}{\mathrm{O}}_{2}\left(\mathrm{g}\right)+2{\mathrm{H}}_{2}\mathrm{O}\left(\mathrm{l}\right)$ If we react $2,37\phantom{\rule{2pt}{0ex}}\mathrm{grams}$ of diborane, how many grams of water would we expect to produce?
2. Sodium azide is a commonly used compound in airbags. When triggered, it has the following reaction: $2{\mathrm{NaN}}_{3}\left(\mathrm{s}\right)\to 2\mathrm{Na}\left(\mathrm{s}\right)+3{\mathrm{N}}_{2}\left(\mathrm{g}\right)$ If $23,4\phantom{\rule{2pt}{0ex}}\mathrm{grams}$ of sodium azide is used, how many moles of nitrogen gas would we expect to produce?
3. Photosynthesis is a chemical reaction that is vital to the existence of life on Earth. During photosynthesis, plants and bacteria convert carbon dioxide gas, liquid water, and light into glucose ( $\mathrm{C}{}_{6}\mathrm{H}{}_{12}\mathrm{O}{}_{6}$ ) and oxygen gas.
1. Write down the equation for the photosynthesis reaction.
2. Balance the equation.
3. If $3\phantom{\rule{2pt}{0ex}}\mathrm{moles}$ of carbon dioxide are used up in the photosynthesis reaction, what mass of glucose will be produced?

#### 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
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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The fundamental frequency of a sonometer wire streached by a load of relative density 's'are n¹ and n² when the load is in air and completly immersed in water respectively then the lation n²/na is
Mukesh Reply
Properties of longitudinal waves
Sharoon Reply

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Source:  OpenStax, Siyavula textbooks: grade 10 physical science [caps]. OpenStax CNX. Sep 30, 2011 Download for free at http://cnx.org/content/col11305/1.7
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