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What is a Mole?
What is a Mole?
This is a mole:
But in science we talk about different moles.
A mole is an amount just like how a pair, or a dozen is an amount.
One mole, also known as Avogadro's number, is 6.02 x 1023.
Non-numerical Words for Quantities:
a couple - 2
a dozen - 12
a score - 20
a gross - 12 dozen
A mole is significant because a mole of atoms weighs exactly the atomic weight in grams.
For example, the atomic mass of hydrogen is 1.01 AMU and one mole of hydrogen atoms will weigh 1.01 grams.
Another example, one mole of carbon atoms weighs approximately 12 grams. Half a mole of carbon atoms, 3.01 x 1023 carbon atoms, will weigh approximately 6 grams.
Molar Mass
Molar Mass
Molar mass is the weight in grams that one mole of something weighs.
The molar mass of any element is the value of its atomic mass in grams. For example, atom of hydrogen weighs 1.01 AMU, and one mole of hydrogen atoms weigh 1.01g
The molar mass of any compound is the combined mass of all the atoms in its formula.
For example the molar mass of CO2 is the weight of one carbon and two oxygen, or 12.01g + 2(16.00)g = 44.01g
Weighing as a form of counting
Weighing as a form of counting
It isn't practical to try to count the number of atoms in a chemical sample, but it is information that a chemist needs.
Chemists use the mass of a chemical sample to determine the number of atoms or molecules in that sample.
To determine the number of atoms in a sample
Find the atomic mass of that element
Divide the weight by the atomic mass. This is the number of moles in the sample.
Multiply the number of moles by avogadro's number.
We can also use dimensional analysis to determine the number of moles.
The atomic mass can be used as a conversion factor between grams and moles
Avogadro's number can also be a conversion factor between moles and number of atoms
Example:
Example:
Which sample has more atoms?
100g of Iron? or 10g of hydrogen?
Iron has an atomic mass of 55.85 g/mol
Dividing 100g by the atomic mass of 55.85 = 1.79 moles
1.79 moles times 6.02 x 1023 = 1.08 x 1024
Hydrogen has an atomic mass of 1.01 g/mol
Dividing 10g by the atomic mass of 1.01 = 9.90 moles
9.90 moles times 6.02 x 1023 = 5.96 x 1024
1.08 x 1024 Iron atoms
5.96 x 1024 Hydrogen atoms
There are more Hydrogen atoms
There are more Hydrogen atoms
Practice
Practice
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