The Mole: A Measurement of Matter

Chemical QuantitiesChapter 10Section 1

Vocabulary

• Mole– The amount of a substance that contains 6.02 x

1023 representative particles of that substance.• Avogardro’s number– The number of representative particles contained

in one mole of a substance; equal to 6.02 x 1023 particles.

Vocabulary

• Representative particles– The smallest unit into which a substance can be

broken down without a change in composition, usually atoms, molecules, or ions.

• Molar Mass• A term used to refer to the mass of a mole of any

substance.

State Standards

• 5.3 Use the mole concept to determine number of particles and molar mass for elements and compounds.

• 5.4 Determine percent compositions, empirical formulas, and molecular formulas.

Key Questions

• How can you convert among the court, mass, and volume of something?

• How do chemists count the number of atoms, molecules, or formula units in a substance?

• How do you determine the molar mass of an element and of a compound?

Measuring Mass

• Knowing how the count, mass, and volume of an item related to a common unit allows you to convert among these units.

What is a Mole?

• The mole allows chemists to count the number of representative particles in a substance.

• A mole is 6.02 x 1023 representative particles– SI unit for measuring the amount of a substance

• Avogadro’s number is 6.02 x 1023

Molar Mass

• The atomic mass of an element expressed in grams is the mass of a mole of the element.

• The mass of a mole of an element is the molar mass.

The Mass of a Mole of a Compound

• To calculate the molar mass of a compound, find the number of grams of each element in one mole of the compound. Then add the masses of the element in the compound.

Assessment

• How many particles does one mole of any substance represent?– 6.02 x 1023 representative particles of a substance

• How can you convert the number of atoms of any substance of moles?– Multiply the number of atoms by the conversion

factor 1 mole equals 6.02 x 1023 representative particles

Assessment

• What is the molar mass of Al2(CO3)3?– Al• 27 g/mol * 2 = 54 g/mol

– C• 12 g/mol * 3 = 36 g/mol

– O• 16 g/mol * 9 = 144 g/mol

– Total = 234 g/mol

Summary

• Knowing how to count, mass, and volume of an item relate to a common unit allows you to convert among these units.

• The mole allows chemists to count the number of representative particles in a substance.

• The atomic mass of an element expressed in grams is the mass of a mole of the element.

Summary

• To calculate the molar mass of a compound, find the number of grams of each element in one mole of the compound. Then add the masses of the elements in the compound.