Basic chemistry help for students and teachers

 

Interactive Chemistry Worksheets for Students

 

Periodic table

Naming compounds

Basic formula

Simple compounds

Ionic compounds 1

Ionic compounds 2

Chemical suffixes

Old chemical names

Hydrocarbons - Alkanes

Alkanes, alkenes & alkynes

Alkanols to alkanoic acids

 

Common compounds

Common formula quiz

Acids, bases and salts

Covalent compounds

Printable worksheets
 

 

 

What is the mole concept?

The mole concept is in chemistry used to calculate the quantity or amount of chemical substances that are used and produced in a chemical reaction.

There are various words in English that are associated with various quantities as show by the table below.

Terms and quantities

Term Dozen Century Gross Ream Millennium
Quantity 12 100 144 500 1 000

In Chemistry the quantities of a dozen, a century, a gross, ream and millennium are far too small.

Even a million is too small. One million atoms of iron weighs 0.0000000000000000928 grams!

Chemist’s measure atomic particles using a large QUANTITY called the mole.

One mole is equal to 602214179000000000000000 or 6.022 x 1023 particles.

Scientists have defined a mole as the number of carbon atoms in exactly 12 grams of carbon-12.

This number is called AVOGADRO’S NUMBER.

Amedeo Avogadro was an Italian physicist whose work lead to the development of the mole.

One mole is 6.022 x 1023 particles

Symbol and unit for the mole

The symbol for the number of moles is n. The unit used in measurement is the mol.

A description of the particle should be included. In Chemistry the particles may be atoms, ions, molecules or sub-atomic particles like the electron.

Shorthand notation

n(Fe) = 1 mol

n(H2O) = 1.5 mol

n(OH-) = 0.25 mol

n(e-) = 0.1 mol

Means

1 mole of iron atoms

1.5 moles of water molecules

0.25 moles of hydroxide ions

0.1 moles of electrons

 

Moles, elephants and water molecules

1. How many elephants are there in one mole of elephants?

 

n(elephants) = 1 mol

Comment:

The equation 'n(elephants) = 1 mol ' says, "the number of moles of elephants is one."

A lower case n is used for the number of moles. What's inside the brackets is used identify what we are talking about. Moles of what?  Kangaroos, water molecules or elephants.

 

N(number of elephants) = 6.022 x 1023

Comment:

The equation 'N(number of elephants) = 6.022 x 1023 ' says the "the number of elephants is 6.022 x 1023 "

An upper case N is used for the number of particles. What's inside the brackets (?) is used identify what we are talking about. We need to describe the number of what?

 

2. How many moles of elephant legs are there in one mole of elephants?

n(elephants) = 1 mol

n(elephants legs) = 4 mol

 

3. How many moles of elephant ears are there in one mole of elephants?

n(elephants) = 1 mol

n(elephant ears) = 2 mol

 

4. How many moles of elephant trunks are there in one mole of elephants?

n(elephants) = 1 mol

n(elephant trunks) = 1 mol

 

5. What is the number of ears and trunks in one mole of elephants?

n(elephants) = 1 mol

N(elephant ears and trunks) = 3 x 6.022 x 1023

N(elephant ears and trunks) = 1.8066 x 1024

 

6. How many water molecules are there in one mole of water?

n(H2O) = 1 mol

Let N = number of water molecules.

N = 6.022 x 1023

 

7. How many moles of hydrogen atoms are there in one mole of water molecules?

n(H2O) = 1 mol

n(H atoms) = 2 mol

 

8. How many moles of oxygen atoms are there in one mole of water molecules?

n(H2O) = 1 mol

n(O atoms) = 1 mol

 

9. How many moles of atoms are there in one mole of water molecules?

n(H2O) = 1 mol

n(atoms) = 3 mol

 

10. How many atoms are there in one mole of water molecules?

 n(H2O) = 1 mol

N(atoms) = 3 x  6.022 x 1023

N(atoms) = 1.8066 x  1024