​How can the mole be used in to help us understand chemistry?

​Let's review a few facts.

1. Atoms and molecules ​are unimaginably small.

   1. "there a​ there are more molecules in a bottle of water then there are bottles of water in all the oceans on earth

Even more mind bending:

1. There are 1.67 x 10²¹ or 1.67 sextillion water molecules in a drop of water.

2. There are 5.01 x 10²¹ or about 5 sextillion atoms in a drop of water.

​

These numbers are incomprehensible to our human brains​.

Yet, as chemistry students, we need to understand and use atoms and molecules to ​all the time.​

Mass and moles-atoms

Here is how we measure our moles.

It turns out the the atomic mas of any element in grams is 1 mole of that element.

So, the atomic mass of carbon is​ 12.011 amu.

Therefore, 12.011g of carbon = 1 mole or 6.022x10²³atoms of carbon.

​Calcium has an atomic mass of 40.08 amu so 1 mole of Ca has a mass of 40.08g

​

Let's have you practice.​

Mass andMoles

It's easier to measure mass then to try to count the individual particles.

Moles and Mass-compounds

Definition of molar mass- The mass in grams of any element or compound is equal to 1 mole.

Nitrogen gas has the molecular formula of N₂. The molar mass can be calculated by:

​atomic mass of nitrogen= 14.007amu, Since there are 2 nitrogen atoms in the formula N_2, 14.007 x2 = 28.014. Simply write this as a molar mass like this: 28.014g N₂ per mole or 28.014/mole.

​Another example​:

table salt has a formula of NaCl. To find the molar mass add the atomic mass of Na and Cl and then write as grams per mole.

Na= 22.990amu

Cl= +35.453amu​

58.443g per mole or 58.443g​

mole​​

Let's try some practice problems.

Summary

So why moles?

We measure moles by mass because mass is easy to measure in lab.

It would be impossible to count individual atoms or molecules because they are so small.

If we could count atoms of molecules at a rate of 10 million per second it​ it would take 2 billion years to the atoms in one mole. Who has that kind of time?

​

Moles be crazy!