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Problem : One kg solution has 0.6 % of urea (w/w) in it. If the molar mass of urea is 60 g m / m o l - 1 , then determine the moles of urea present in the solution.

Solution : The mass of solute (oxalic acid) is obtained as :

g B = x X g S 100 = 0.6 X 1000 100 = 60 g m

n B = g A M O = 60 60 = 1

Mass percentage of oleum

Sulphuric acid is formed by passing S O 3 gas through water in accordance with following chemical equation :

S O 3 + H 2 O H 2 S O 4

When all water molecules combine to form sulphuric acid, there remains free S O 3 molecules. Oleum is the name given to this mixture of concentrated sulphric acid solution and free S O 3 . From the point of view reaction between oleum and other solution, S O 3 molecules are as good as sulphuric acid molecule as it reacts with available water molecules to form sulphuric acid molecule.

If an oleum solution has x percent of free S O 3 (x gm in 100 gm of oleum), then the equivalent amount of sulphuric acid is calculated using mole concept :

1 mole of S O 3 1 mole of H 2 S O 4

80 gm of S O 3 98 gm of H 2 S O 4

H 2 S O 4 that can be formed from x gm of SO3 is 98 x 80 . Total mass of H 2 S O 4 is sum of H 2 S O 4 in the liquid form and H 2 S O 4 that can be formed when H 2 S O 4 reacts with water :

total mass of H 2 S O 4 = 100 x + 98 x 80 = 100 + 18 x 80

Considering equivalent H 2 S O 4 mass in calculation, the mass percentage of H 2 S O 4 in oleum is given as :

y = Total mass of H 2 S O 4 mass of oleum = 100 + 18 x 80 100 X 100 = 100 + 18 x 80

Clearly, equivalent H 2 S O 4 mass percentage is more than 100 %.

Volume percentage (v/v)

The volume percentage is expressed as :

Volume percentage x = Volume of solute B Volume of solution A + B X 100

Volume percentage x = V B V S X 100 = V B V A + V B X 100

Strength of solution (w/v)

The strength of solution is expressed as :

Strength of solution S = Mass of solute (B) in grams Volume of solution in litres

S = g B V L

The unit of strength is “grams/liters”. Note that strength of solution is not a percentage – rather a number The symbol V L denotes volume of solution in litres, whereas V CC denotes volume of solution in cc. If volume is expressed in cc, then the formula of strength is :

S = g B X 1000 V c c

Problem : Determine the numbers of moles of sulphuric acid present in 500 cc of 392 gm/litre acid solution.

Solution : In order to find the moles of sulphuric acid, we need to find its mass in the given volume.

g B = S X V L = 392 X 0.5 = 196 g m

The moles of H 2 S O 4 M 0 = 2 + 32 + 4 X 16 = 98 is :

n B = 196 98 = 2

Molar concentration

The conversion of concentration of the solution into molar mass of the solute is a two steps process. In the first step, we calculate the mass of the solute and then in second step we divide the mass of the solute by molecular weight to determine the moles of solute present in the solution. We can think of yet a direct measurement of molar concentration. This will enable us to calculate moles of solute in one step.

Mole fraction

Mole fraction of solute ( χ B ) is defined as :

Molefraction χ B = Mole of solute B Mole of solvent A + Mole of solute B

χ B = n B n A + n B

Similarly, mole fraction of solvent (B) or other component of solution is :

χ A = n A n A + n B


χ A + χ B = 1

Problem : The mass fraction of ethyl alcohol in a sample of 1 kg of aqueous ethyl alcohol solution is 0.23. Determine mole fraction of ethyl alcohol and water in the solution.

Solution : The mass of ethyl alcohol and water are calculated as :

g B = mass fraction X mass of solution = 0.23 X 1000 = 230 g m

mass of solvent = g A = mass of solution mass of ethyl alcohol = 1000 230 = 770 g m

The moles of of ethyl alcohol and water are :

n B = 230 M C 2 H 5 O H = 230 2 X 12 + 5 X 1 + 16 + 1 = 230 46 = 5

n A = 770 M H 2 O = 230 18 = 770 18 = 42. 8

The mole fraction of ethyl alcohol and water are :

χ B = n B n A + n B = 5 42.8 + 5 = 5 47.8 = 0.104

χ A = 1 0.104 = 0.896

Questions & Answers

anyone know any internet site where one can find nanotechnology papers?
Damian Reply
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
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
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
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.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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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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