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Moles and mass

  1. Complete the following table:
    Element Relative atomic mass (u) Sample mass (g) Number of moles in the sample
    Hydrogen 1.01 1.01
    Magnesium 24.31 24.31
    Carbon 12.01 24.02
    Chlorine 35.45 70.9
    Nitrogen 42.08
  2. How many atoms are there in...
    1. 1 mole of a substance
    2. 2 moles of calcium
    3. 5 moles of phosphorus
    4. 24 , 31 g of magnesium
    5. 24 , 02 g of carbon

Molar mass

Molar mass

Molar mass (M) is the mass of 1 mole of a chemical substance. The unit for molar mass is grams per mole or g · mol - 1 .

You will remember that when the mass, in grams, of an element is equal to its relative atomic mass, the sample contains one mole of that element. This mass is called the molar mass of that element.

You may sometimes see the molar mass written as M m . We will use M in this book, but you should be aware of the alternate notation.

It is worth remembering the following: On the periodic table, the relative atomic mass that is shown can be interpreted in two ways.

  1. The mass of a single, average atom of that element relative to the mass of an atom of carbon.
  2. The mass of one mole of the element . This second use is the molar mass of the element.
The relationship between relative atomic mass, molar mass and the mass of one mole for a number of elements.
Element Relative atomic mass (u) Molar mass ( g · mol - 1 ) Mass of one mole of the element (g)
Magnesium 24,31 24,31 24,31
Lithium 6,94 6,94 6,94
Oxygen 16 16 16
Nitrogen 14,01 14,01 14,01
Iron 55,85 55,85 55,85

Calculate the number of moles of iron ( Fe ) in a 11 , 7 g sample.

  1. If we look at the periodic table, we see that the molar mass of iron is 55 , 85 g · mol - 1 . This means that 1 mole of iron will have a mass of 55 , 85 g .

  2. If 1 mole of iron has a mass of 55 , 85 g , then: the number of moles of iron in 111 , 7 g must be:

    111 , 7 g 55 , 85 g · mol - 1 = 2 mol

    There are 2 moles of iron in the sample.

You have a sample that contains 5 moles of zinc.

  1. What is the mass of the zinc in the sample?
  2. How many atoms of zinc are in the sample?
  1. Molar mass of zinc is 65 , 38 g · mol - 1 , meaning that 1 mole of zinc has a mass of 65 , 38 g .

  2. If 1 mole of zinc has a mass of 65,38 g , then 5 moles of zinc has a mass of: 65,38 g × 5 mol = 326,9 g (answer to a)

  3. 5 × 6 , 022 × 10 23 = 30 , 115 × 10 23

    (answer to b)

Moles and molar mass

  1. Give the molar mass of each of the following elements:
    1. hydrogen
    2. nitrogen
    3. bromine
  2. Calculate the number of moles in each of the following samples:
    1. 21 , 62 g of boron ( B )
    2. 54 , 94 g of manganese ( Mn )
    3. 100 , 3 g of mercury ( Hg )
    4. 50 g of barium ( Ba )
    5. 40 g of lead ( Pb )

An equation to calculate moles and mass in chemical reactions

The calculations that have been used so far, can be made much simpler by using the following equation:

n ( number of moles ) = m ( mass of substance in g ) M ( molar mass of substance in g · mol - 1 )
Remember that when you use the equation n = m M , the mass is always in grams ( g ) and molar mass is in grams per mol ( g · mol - 1 ).

Questions & Answers

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
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
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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