5-3 Balancing with Moles• Objectives:

– Define mole.– Explain how moles are used in chemical

reaction

Counting with Moles• Chemists need a practical unit to count

things.• The mole is chemist practical counting

unit.• 1 mole of matter = 6.022 x 1023 particles• This number is known as Avagadro’s

number.– 1 mole of Fe = 6.022 x 1023 iron atoms– 1 mole of Cl- = 6.022 x 1023 Chlorine ions.

• Moles of different substances have different masses.

Are there the same number of balls?

Molar mass• The mass of one mole of substance.• Carbon has a atomic mass of 12 amu.• One mole of carbon has a mass of 12 g.• One mole of any element equal to the

mass number of grams.• One mole of carbon does not equal one

mole of oxygen.

Converting Mass to Moles

Converting Mass to Moles

Converting Mass to Moles

Converting Mass to Moles

Converting Mass to Moles

Converting Mass to Moles

• Each line shows the conservation of mass.

• There is no law that states conservation of molecules.

• The mass numbers can be express in g/mol.

5-3 Summary• The law of conservation of mass says

that mass can not come from nowhere or simply disappear.

• To show mass is conserved during reaction, chemical equations must be balanced.

• Instead of number of particles, moles are used because chemical reactions involve very large numbers of particles.

• The mass of a reactant or product can be calculated by using chemical equations and molar mass.