Section 4: Moles of

CompoundsChapter 7: Chemical Composition

Learning Goals0Convert between grams and moles.0Convert between grams and

number of atoms or molecules.0Convert between moles of a

compound and moles of a constituent element.

0Convert between grams of a compound and grams of a constituent element.

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.

Chemical Formulas and the Mole0Determine the number of moles of Cl- ions in 2.50 mol of ZnCl2.

0How many moles of oxygen atoms are present in 5.50 mol of diphosphorus pentoxide.

Chemical Formulas and the Mole0Determine the number of moles of sulfate ions present in 3.00 mol of Iron (III) sulfate.

0Calculate the number of moles of each element in 1.25 mol of C6H12O6.

The Molar Mass of Compounds0The 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.

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

The Molar Mass of Compounds0Determine the molar mass of each compound:

0NaOH

0CaCl2

0Potassium acetate

The Molar Mass of Compounds0Determine the molar mass of each compound:

0C2H5OH

0HCN

0Carbon tetrachloride

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.

Converting Moles to Mass0What is the mass of 3.25 mol of H2SO4?

0What is the mass of 4.35 x 10-2 mol of zinc chloride?

Converting Mass to Moles0The conversion factor is the inverse of the molar mass of the compound.

Converting Mass to Moles0Determine the number of moles present in each compound:

022.6 g AgNO3

06.50 g ZnSO4

035.0 g hydrochloric acid

Converting Mass to Particles0First, convert mass to moles of compound with the inverse of molar mass.

0Then, convert moles to particles with Avogadro’s number.

Converting Mass to Particles0A sample of ethanol (C2H5OH) has

a mass of 45.6 g.

0How many carbon atoms does this sample contain

0How many hydrogen atoms are present?

0How many oxygen atoms are present?

Converting Mass to Particles0A sample of sodium sulfite has a mass of 2.25 g

0How many Na+ ions are present?

0How many SO32- ions are

present?