<< Chapter < Page Chapter >> Page >

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

Clearly,

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

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
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
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
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
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.
Bharti
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
Daniel
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!





Source:  OpenStax, Stoichiometry. OpenStax CNX. Jul 05, 2008 Download for free at http://cnx.org/content/col10540/1.7
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Stoichiometry' conversation and receive update notifications?

Ask