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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

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SUYASH
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s. Reply
of graphene you mean?
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or in general
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in general
s.
Graphene has a hexagonal structure
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Cied
types of nano material
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I start with an easy one. carbon nanotubes woven into a long filament like a string
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many many of nanotubes
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what is the function of carbon nanotubes?
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I'm interested in nanotube
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what is nanomaterials​ and their applications of sensors.
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what is nano technology
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what is system testing?
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preparation of nanomaterial
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Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
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AMJAD
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AMJAD
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
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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
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name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
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silver nanoparticles could handle the job?
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not now but maybe in future only AgNP maybe any other nanomaterials
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Hello
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I'm interested in Nanotube
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this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
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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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