Section 3: Moles of CompoundsChemical Composition

Learning Goals0 Recognize the mole relationships shown by a

chemical formula.

0 Calculate the molar mass of a compound.

0 Convert between the number of moles and mass of a compound.

0 Apply conversion factors to determine the number of atoms or ions in a known mass of a compound.

Chemical Formulas and the Mole0Chemical formulas indicate the

numbers and types of atoms contained in one unit of the compound.

Chemical Formulas and the Mole0One mole of CCl2F2 contains one

mole of C atoms, two moles of Cl atoms, and two moles of F atoms.

Practice0Determine the number of moles of

Cl- ions in 2.50 mol of zinc chloride.

Practice0How many moles of oxygen atoms

are present in 5.00 mol of diphosphorus pentoxide?

The Molar Mass of Compounds0 The molar mass of a compound equals

the molar mass of each element, multiplied by the moles of that element in the chemical formula, added together.

0 The molar mass of a compound demonstrates the law of conservation of mass.

Practice0Determine the molar mass of

hydrogen cyanide.

Practice0Determine the molar mass of

calcium chloride.

Converting Moles to Mass0For elements, the conversion factor

is the molar mass of the compound.

0The procedure is the same for compounds, except that you must first calculate the molar mass of the compound.

Practice0What is the mass of 3.25 mol of

sulfuric acid?

Converting Mass to Moles0The conversion factor is the inverse

of the molar mass of the compound.

Practice0Determine the number of moles

present in 35.0 g of hydrochloric acid.

Converting Mass to Particles0Convert mass to moles of

compound with the inverse of molar mass.

0Convert moles to particles with Avogadro’s number.

Practice0A sample of sodium sulfite has a

mass of 2.25 g.0How many sodium ions are present?

0How many sulfite ions are present?

0What is the mass in grams of one formula unit of sodium sulfite?