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Concept of the Mole

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Hannah Beck

on 20 March 2014

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Transcript of Concept of the Mole

Concept of the Mole
The Mole
Chemical reactions usually happen at levels where using grams, or even absolute numbers of atoms/molecules/ions as units, would be confusing and complicated.
The solution is the mole- a unit used for counting particles in elements, compounds, or ionic substances
Just like there are about 110 elements on the periodic table, there are 6.022x10^23 atoms, formula units, or molecules, in a single mole
6.022x10^23 is known as Avogadro's number
Avogadro's number is 602 sextillion particles, an inconceivably large amount
To help you understand how big Avogadro's number really is, here are some examples...

Conversions: Calculating moles to grams
Converting moles to grams can be a confusing concept for students to grasp, but referring to a chart can be helpful

Grams Moles Particles


Molar Mass


Avogadro's number

Molar Mass
equals the atomic mass of the element. Molar mass is used as a conversion factor from grams to moles and grams to particles and visa versa
Conversion Examples
Grams Moles Particles

Molar Mass

Avogadro's number
How many grams of nitrogen are in 35 moles of nitrogen?

35 moles of nitrogen x 14.007 nitrogen grams
----------------- ----------------- = 490.245 grams of Nitrogen
1 1 mole

1. To convert moles to grams, use the molar mass of Nitrogen
14.007g Nitrogen = 1 mole Nitrogen
2. Use it as a conversion factor to cancel out moles, so only grams remain
3. Don't forget to use significant figures

For this conversion, Avogadro's number is used as a conversion factor
Molar mass is not needed because we are NOT going from, or to, grams

Example of Moles to Atoms
How many atoms of vanadium are in 13.5 moles of vanadium?

13.5 moles of Vanadium 6.022 x 10^23 atoms of Vanadium
------------------ x -------------------------- = 8.13 x 10^24 atoms of Vanadium
1 1 mole of Vanadium

1. 1 mole= 6.022x10^23 atoms, formula units, or molecules
2. Moles have to cancel out in order to achieve atoms, so multiplication is used

Calculating Moles to Molecules
How many molecules of Magnesium Sulfate are in 4.1 moles of Magnesium Sulfate?

Formula: MgSO4

4.1 moles of MgSO4 6.022 x 10^23 molecules of MgSO4
---------------- x -------------------------- = 2.5 MgSO4 molecules
1 1 mole of MgSO4
How is the Mole used in Chemistry?

It is used in almost every chemical calculation
1 mole of a substance can be compared to 1 mole of another substance, since they are both in the same unit
This can lead to discoveries about the substances' properties
When used in experiments, one measurement can be converted into others
Importance of Writing Formulas

If a chemical formula is incorrect, there will be incorrect proportions
If the proportions are not correct, experiments will result in incorrect conclusions
The percent composition of substances in solutions could be messed up
Example: IV bags
A chemical formula must be correct in order to balance a chemical equation
Nomenclature is the foundation of chemistry and is crucial for chemical equations
Works Cited
How big is a mole? (examples)? (n.d.). Retrieved from http://answers.yahoo.com/question/index?qid=20081115172343AAKoVWM

How big is a mole? (Not the animal, the other one.) - Daniel Dulek. (n.d.). Retrieved from

Why Do Chemists Use the Mole? - Ask.com. (n.d.). Retrieved from http://www.ask.com/question/why-do-chemists-use-the-mole
Formula Units
When a substance is ionic

When a substance is a compound

When it is a single element
Avogadro's Number
If you covered the earth in a mole of doughnuts, the depth would be
5 miles
If 1 mole of pennies could be distributed to the world's population,
every person could spend a million dollars per hour,
every hour, for the rest of their lives
Moles Atoms/molecules/formula units
1. There are 6.022x10^23 molecules of MgSO4 in 1 mole MgSO4
2. Cross moles out to obtain the number of MgSO4 molecules
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