3.1 – Chemical Equations + = Reacts with -> = Yields / Produces Reactants = Substances on the left side of the arrow Products = Substances on the right side of the arrow
Balancing Reactions For now the old method is OK. We’ll learn more about balancing more complicated (redox) reactions later 1.Write correct formulas 2.Balance elements / ions that only appear once on each side 3.Balance others 4.Balance O and H 5.Check
3.1 – Balancing Equations Most can be done by inspection for now! Ex – methane + oxygen -> carbon dioxide + water
Reaction Example CH 4 (g) + 2 O 2 (g) CO 2 (g) + 2 H 2 O (g)
3.1 – Balancing Equations Ex – sodium + water -> sodium hydroxide + hydrogen gas
AP Question 4 -Changed for 2008 -Now want BALANCED NET-IONIC -Ask you an additional question -No “choice” in the questions **See additional packet for practice Be sure to know: -Single displacement (metal and nonmetal) -Double displacement -Combustion -Acid / Base (we’ll cover more later)
3.3 – Formula Weights Atomic mass – Mass of an atom in amu (atomic mass unit) 1 amu = 1/12 of the mass of a Carbon-12 atom Mole = Amount of a substance based on particles Avogadro’s Number = # of particles in 1 mole; Based on 12 grams of Carbon–12 = 6.02 x 10 23 Molar Mass = Mass needed to obtain Avogadro’s Number of particles for any substance.
3.5 – Empirical Formulas from Lab Data Determining Molecular Formula -Need to know approximate Molar Mass -Need to know Empirical Formula -Molecular Formula is a multiple of the Empirical Formula
Practice Problem Caproic acid, which is responsible for the foul odor of dirty socks, is composed of C, H and O atoms. Combustion of a 0.225 g sample of this compound produces 0.5112 g carbon dioxide and 0.209 g water. Water is the empirical formula of caproic acid? If the molar mass of the acid is 116 g/mol, what is the molecular formula?
3.6 – Quantitative Information from Balanced Equations -Stoichiometry – Coefficients (numbers in front of substances in a balanced equation) provide relative numbers of moles in the reaction Examples: