The content that complies with is the substance of class 8. In this lecture us cover the Mole and Avagadro"s Number and the calculations for Molar Mass and also conversions utilizing moles.

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The MOLE (mol) is a unit the measurement that is the lot of a pure substance containing the same number of yellowcomic.comical devices (atoms, molecule etc.) as there space atoms in precisely 12 grams that carbon-12 (i.e., 6.022 X 1023).

So the mole is the title used for the lot 6.022 x 1023 much the same way the native "dozen" is provided for the lot 12.

So if you had actually a mole the donuts friend would have 6.022 x 1023 donuts and also a serious stomach ache.

We usage the mole (mol) to stand for the quantity of building materials in yellowcomic.comistry due to the fact that the number of atoms and also molecules in every substance is therefore large. The value offered 6.022 x 1023 is called Avagadro"s number because that the scientist that uncovered the number of atoms in 12 grams that carbon 12. Why usage 12 grams? This is the theoretical atomic mass that the Carbon-12 isotope (6 protons and also 6 neutrons). This way that the atom mass or atomic weight (12 grams) of carbon is same to exactly 1 mole the carbon.

Using carbon as a reference, the atom weights you see in the periodic table are also equal come one mole of those substances:


Lithium for instance has an atomic mass of 6.941 grams and also this is equal to one mole the lithium. This is why we state the atomic and also molecular masses in devices of grams every mole or g/mol.

What can we execute with moles? We usage the unit to do calculations based on balanced yellowcomic.comical equations. We usage the stoichiometry (fancy means of saying mole ratios in an equation) to do predictions about how lot product will certainly be make or reactant necessary if we understand one mole quantity in a reaction.

Moles the a Substance and the molecular Weight

The Molar fixed or Molecular weight (interchangeable terms so lengthy as we space on Earth) the a problem is the total of all the individual masses the the elements it contains. To usage our old girlfriend water together an example:

One mole of Water is written of 1 mole that Oxygen and two moles of Hydrogen. The fixed of oxygen equal to one mole the oxygen is 15.998 grams and the mass of one mole the hydrogen is 1.008 g. If we complete up the gram amounts of each facet in the water molecule = 15.998g/mol + 2(1.008g/mol) we gain the molar fixed of water = 18.014g/mol.

So if us had precisely 18.014g of water we would have actually 1 mole the water.

Practice: Mole and Molar Mass

Mole Relationships

The reason the mole is so crucial is because we usage the mole as the unit for most of the relationship in yellowcomic.comistry. Reactions are balanced based ~ above the number of moles the each aspect in the reaction, solution concentrations are an extremely often defined in regards to moles every liter or moles per kg of solvent and also we have already seen that the molecules or atom of an aspect are reported together moles the the substance rather than the individual count of their particles.

Let"s start the relationship conversation with the relationship in between the mole and the AMU.

An AMU is 1/12 the massive of a Carbon-12 atom which follow to the regular table weighs ~12g. This method that 1 AMU ≈ 1g right? and thus Carbon has actually a fixed of 12amu, correct? but wait, this can not be the mass of a single carbon atom right? They space really, yes, really tiny. And that is correct, the mass presented in the periodic table is actually the massive of 6.022 x 1023 carbon atom or a mole that carbon atoms. Therefore in reality, 1 AMU = 1.66 x 10-24g and also while a carbon atom weighs 12 AMU, the mass presented in the routine table is

12 atoms x 1.66 x 10-24g x 6.022 x 1023 atoms/ mol= 12 g/mol

So a single carbon atom weighs 12 amu if a mole that carbon atom weighs 12.01g/mol.

Mole Calculations

There room plethora of calculations that have the right to be performed using the unit of moles together the intermediate. Ns am walking to testimonial a few of lock now and also then you will view as we progression through later topics that moles are important to those calculations together well.

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Typical mole calculations:

1) Calculation that the Molecular weight or Molar mass of a compound

The molar fixed of a compound additionally often called the molecular weight while top top Earth, is just the amount of all the individual element masses in the compound. You use the periodic table together a recommendation for this masses and also total castle up:

For example, if we desire to full the molar mass of Aluminum Sulfate Al2(SO4)3 , we require to identify the number and mass of each element in the compound. For Aluminum Sulfate the totals space 2 Al, 3 S and also 12 O. So here is the math using the atomic masses provided in the periodic table:

2(26.98 g/mol) + 3( 32.07 g/mol) + 12(16.00 g/mol) = 342.17 g/mol

2) Conversion from Grams to moles or moles to Grams

Once you know the molar massive of a compound, you can use the mass to identify the lot of moles in a gram lot of the problem or vice versa, you deserve to calculate the variety of grams in a mole quantity of the substance.

Here room some examples:

How plenty of moles space in 55.4g that Aluminum Sulfate?

The calculation is set up prefer a conversion through the molar fixed of Aluminum Sulfate together the conversion factor:

55.4g Al2(SO4)3 x 1 mol Al2(SO4)3/342.17 g Al2(SO4)3 = 0.162 mol Al2(SO4)3

Or, How numerous grams the Al2(SO4)3 room in 6.34 mole of Al2(SO4)3?

6.34 mol Al2(SO4)3 x 342.17g Al2(SO4)3/ 1 mol Al2(SO4)3 = 2.17 x 103 Al2(SO4)3

3) Conversion to molecule or Atoms

In addition to being a unit because that molar mass, the mole is additionally the gateway between the fixed of a substance and its atom or molecules.

For Example, if request how many molecules the Al2(SO4)3 room in th 55.4 g the Al2(SO4)3 over we simply need to very first calculate the variety of moles as before and also then usage Avagadro"s number to transform the mole to molecules:

55.4g Al2(SO4)3 x 1 mol Al2(SO4)3/342.17 g Al2(SO4)3= 0.162 mol Al2(SO4)3

0.162 mol Al2(SO4)3 x 6.022 x 1023 molecules Al2(SO4)3/ 1 mol Al2(SO4)3 =

9.76 x 1022 Molecules Al2(SO4)3

Furthermore if we ongoing the problem and also asked how numerous Aluminum atoms to be in the 55.4 g the Al2(SO4)3?

Well the is a simple continuation. We simply need to main point by the variety of atoms that Aluminum in the compound:

9.76 x 1022 Molecules Al2(SO4)3 x 2 atoms Al/ 1 molecule Al2(SO4)3 = 1.95 x 1023 Al atoms

Let"s practice some more: