This Means There Are 6.02 X 1023 Entities in One Mole

SCH 3U Holy Moley!!!

A mole is the amount of a substance containing 6.02 x 1023 of anything. The symbol for moles is: n, units; mol.

(6.02 x 1023 is Avogadro’s number or constant!)

This means there are 6.02 x 1023 entities in one mole!!

·  How many donuts would make up two moles of donuts???

·  How many elephants in ½ of a mole?

A mole is a very large number (602 000 000 000 000 000 000 000), but….because we use for the amount of atoms, ions or molecules, and these are very small, a mole is actually a convenient, observable amount to measure and handle.

The story of the mole gets even more exciting!

Recall that compounds are made up of more than one type of atom. 1 mole of a compound will also contain specific amounts of each type of atom.

Example:

CO2 is made up of 1 atom of carbon and 2 atoms of oxygen.

How many atoms of carbon are in one mole of CO2??

Look at the formula…the subscript for carbon is 1, therefore one mole of carbon is found in 1 mole of CO2.

How many atoms of oxygen are in one mole of CO2?

Look at the formula….the subscript for oxygen is 2, therefore two moles of oxygen are found in 1 mole of CO2

Example:

N2O5

Molar mass

Molar mass is the mass, in grams, of one mole of a substance. The units for molar mass are g/mol (grams/mole) and the symbol is M.

Fun coincidence!

The mass of one mole of an element is equal to the atomic mass of that element. Wow!!!

Example: 1 mole of Carbon has a mass of 12.01 g/mol (because the atomic mass of carbon is 12.01 u)

Example: What is the molar mass of mercury?

Another fun coincidence!

The molar mass of a compound can be found by using the atomic masses of the elements and the subscripts.

Example: What is the molar mass of H2O?

More mole mania!

The mass of a gaseous substance is hard to measure, but the concept of the mole can still be applied. 1 mole of a gas at STP (standard temp. of 0○C, standard pressure at 1 atm or 101.4 kPa) always occupies 22.4 L.

Example: what volume would 3 mols of oxygen gas occupy?

Example: how many moles of nitrogen gas are found in 47 L of the gas?

Recap

The mole is very flexible way of measuring amounts in chemistry. It can be used to measure materials in 3 ways.

·  By mass – molar mass in g/mol

·  By volume – 22.4 L/ mol at STP

·  By number – 1 mole =6.02 x 1023

Molar Mass Worksheet

Calculate the number of atoms found in:

1) 5 mol of silver

2) 3.25 mol of carbon

3) 100.5 mol of sulfur

Calculate the total number of atoms found in:

1) 5 mol of oxygen gas

2) 2.25 mol of carbon dioxide gas

3) 8.75 mol of pentane

Calculate the number of moles found in:

1) 5.546 X 10 25 molecules of chlorine gas

2) 7.30 X 10 22 atoms of gold

3) 6.02 X 10 23 sulfate ions

Calculate the molar masses of the following chemicals to two decimal places:

1) Cl2

2) KOH

3) BeCl2

4) FeCl3

5) BF3

6) CCl2F2

7) Mg(OH)2

8) UF6

9) SO2

10) H3PO4

11) (NH4)2SO4

12) CH3COOH

13) Pb(NO3)2

14) Ga2(SO3)3