Chemical Equation & Reaction Notes -Chemical reactions – occur when chemical bonds (ionic, covalent) between atoms are broken and new bonds are formed -Chemical equation – used to describe chemical reactions through symbols & numbers

Example of chemical equation: aluminum sulfate plus barium chloride yields aluminum chloride plus barium sulfate Al 2 (SO 4 ) BaCl 2  2 AlCl BaSO 4 Label the following: – Reactants- Products -Coefficients - Subscripts - Produces or yields

Terms or symbols used in equations “+” or “and” - used as divider between reactants or products → yields, reacts, produces, forms, … reversible reaction CATALYST is something that speeds up the reaction, but it is not used as a chemical part of the reaction; written on top of the yield sign Heat or ∆ or MnO 2 or elec

More terms and symbols (s)solid (l)liquid (aq)aqueous, dissolved in water (g) gas NR no reaction

There are 5 types of chemical reactions

#1 - Synthesis Reactants combine to form 1 compound (aka, combination rxn) reactant + reactant  product Basically: A + B  AB Ex : 2 H 2 + O 2  2 H 2 O Ex: C + O 2  CO 2

Synthesis Reaction (continued) Here is another example of a synthesis rxn:

#2 - Decomposition occur when a compound breaks up into 2 or more products (can be elements or compounds) 1 Reactant  Product + Product In general: AB  A + B Ex: 2 H 2 O  2 H 2 + O 2 Ex: 2 HgO  2 Hg + O 2

Decomposition (continued) Another view of a decomposition reaction:

#3 - Single Replacement occur when one element replaces another in a compound (aka, single displacement) AB + C  CB + A Metals must be more reactive in order to replace another metal (called the Activity Series) Zn (s) + HCl (aq)  ZnCl 2 + H 2(g)

#4 – Double Replacement Occurs when 2 ionic compounds “switch partners” and produce 2 different compounds Compound + compound  compound+ compound AB + CD  AD + CB Ex: AgNO 3(aq) + NaCl (s)  AgCl (s) + NaNO 3(aq)

#5 - Combustion occur when a hydrocarbon reacts with oxygen This is also called burning In general: C x H y + O 2  CO 2 + H 2 O Products in combustion are ALWAYS carbon dioxide and water. (incomplete combustion will also produce carbon monoxide)