Ch. 8 – Chemical Equations & Reactions Define a Chemical Reaction Comprised of symbols and formulas that represent the reactant & products of the chemical reaction.

Parts of a Chemical Equation 1. The product and reactant are identified. 2. The formulas for each product & reactant must be correct. Formulas must be neutral. 3. The law of conservation of mass must be satisfied. The formulas on each side of the equation must be balanced.

Coefficients are the whole numbers that appear in front of each formula Ex. 6H 2 O + 6CO 2 C 6 H 12 O 6 + 6O 2 Word Equations – this is where the reactants & products are written in the equation. Ex. 6 mol of water + 6 mol of oxygen Formula equations are in formulas Table 8-2 Symbols used in equations

Reversible reactions are chemical reactions in which the products can reform to the original reactants. Sample Problem 8-1 Sample Problem 8-2

Balancing Chemical Equations 1. If the reactant or product has names convert them to symbols. 2. Balance the chemical equations with the smallest number of coefficients added to each formula. The product & reactant must have the same amount of atoms of each element. Ex. H 2 0 H 2 + O 2 Sample Problems 8-3, 8-4, 8-5

Types of Chemical Reactions 1. Synthesis or Composition - 2 or more substance combine to form a new compound A + B AB (examples) 2. Decomposition – a single compound undergoes a reaction that produces 2 or more simpler substances. AB A + B (examples)

3. Single – Replacement – one element replaces a similar element in compound. A + BC AC + B (examples) 4. Double – Replacement – the ions of 2 compounds exchange places in a aqueous solution to form 2 new compounds. AB + CD AD + CB (examples)

5. Combustion – a substance combines with oxygen releasing a large amount of energy in the form of light & heat. Hydrocarbons are compounds made up of carbon and hydrogen. Ex. Butane, propane, methane In a combustion reaction the reaction contains a hydrocarbon and the product contains CO 2 and H 2 O.