The Mole

The Mole

•Atoms & molecules are extremely small

•The number of individual particles in even a small sample of something is very large

•Therefore, counting the number of particles is not a practical way to measure the sample.

The Mole

•A chemical counting unit (abbreviated “mol”)

•Similar to a dozen, except instead of 12, it’s 602 billion trillion 602,000,000,000,000,000,000,000

•6.02 X 1023 (in scientific notation)

The Mole

6.02 x 1023

• This number is named in honor of Amedeo AvogadroAmedeo Avogadro, who studied quantities of gases and discovered that no matter what the gas was, there were the same number of molecules present in a constant volume of gas.

The MoleThat’s my number!

•The term representative particle refers to the species present in a substance–Usually atoms or molecules

The Mole

Molar RelationshipsA balanced chemical equation can be interpreted in numbers of molecules, but generally chemists interpret equations as “mole-to-mole” relationships.2H2(g) + O2(g) → 2H2O(l)In the equation above: 2 moles of hydrogen gas and 1 mole of oxygen gas produce 2 moles of liquid water.

Molar Relationships

Therefore:H2 & O2 have a 2:1 mole-to-mole ratioO2 & H2O have a 1:2 mole-to-mole ratioH2 & H2O have a 1:1 mole-to-mole ratio

2H2(g) + O2(g) → 2H2O(l)

Molar Relationships

What are the mole-to-mole ratios in the chemical equation above?

N2 + 3H2 → 2NH3

Find the number of moles of NH3 that can be formed from 4.8 mol H2 using the balanced reaction below.

N2 + 3H2 → 2NH3

Molar Relationships

4.8 mol H2

2 mol NH3

3 mol H2

x = 3.2 mol NH3

Find the number of moles of LiNO3 needed to produce 3.2 mol Pb(NO3)4 using the balanced reaction below.

Pb(SO4)2 + 4LiNO3 Pb(NO3)4 + 2Li2SO4

Molar Relationships

3.2 mol Pb(NO3)

4

4 mol LiNO3

1 mol Pb(NO3)4

x = 12.8 mol LiNO3

PracticeProblems

Grab your clicker!(& a calculator)

Consider the balanced chemical reaction:

2Fe + 3 H2S04 → Fe2(SO4)3 + 3H2

How many moles of Fe are required to produce 9 moles of H2?A. 9 molesB. 2 molesC. 4.5 molesD. 6 moles

Question #1

Consider the balanced chemical reaction:2Fe + 3 H2S04 → Fe2(SO4)3 + 3H2

How many moles of Fe2(SO4)3 will be produced if we begin with 17 moles of Fe?A. 17 molesB. 8.5 molesC. 34 molesD. 11 moles

Question #2

Consider the balanced chemical reaction:

2C2H6 + 7O2 → 6H2O + 4CO2

How many moles of carbon dioxide are produced from 1 mole of C2H6?A. 1 molesB. 2 molesC. 7 molesD. 8 moles

Question #3

Consider the balanced chemical reaction:

2C2H6 + 7O2 → 6H2O + 4CO2

How many moles of O2 are required to produce 9 moles of H2O?A. 10.5 molesB. 6 molesC. 9 molesD. 7.5 moles

Question #4

Consider the following chemical reaction:

KOH + H3PO4→ K3PO4 + H2OHow many moles of KOH are required to produce 12.5 moles of H2O?A. 2.5 molesB. 7.5 molesC. 9 molesD. 12.5 moles

Question #5

Consider the following chemical reaction:

KOH + H3PO4→ K3PO4 + H2OHow many moles of H3PO4 are required to produce 9 moles of H2O?A. 3 molesB. 6 molesC. 9 molesD. 7 moles

Question #6