Chapter 7 Sec. 1 Avagadro’s # and Molar Calc. Sec. 2 Relative atomic mass & Chemical Formulas Sec. 3 Formulas and percent composition

Avagadro’s # and Molar Conversions Identify the mole as the unit used to count particles. Use Avagadro’s # to convert between moles and particles Solve problems converting between mass, moles, and particles.

Avagadro’s number Avagardo’s # is the number of particles in one mole of substance. This number does not change. 6.022 X 1023 (atoms, ions, molecules)/mol

Sec. 2 Relative atomic mass and Chemical Formulas Use a periodic table to determine the average atomic mass of elements Infer information about a compound from its chemical formula. Determine the molar mass of a compound from its chemical formula

Relative atomic mass The atomic mass on the periodic table is an average of all isotopes of that compound found in nature. If the percentages of each isotope are known, we can then calculate the average atomic mass. Turn to page 235

Chemical Formulas Covalent cmpd’s formulas represent all atoms present in one molecule of the cmpd. Ionic cmpd’s formulas represent the simpliest ratio of atoms in the cmpd. Calculating molar mass of cmpd’s on page 239.

Sec. 3 Formulas and % Composition Determine a cmpd’s empirical formula from its percent composition Determine the molecular formula of a compound from its empirical formula and its formula mass. Calculate percent composition of a compound from its molecular formula or formula unit.

Section # Formulas Empirical Formula is the reduced formula of a molecule. Molecular Formula is the actual number of atoms in each molecule