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Chapter 8. Chemical Equations and Reactions. Chemical Reactions. Chemical Reaction- one or more substances are changed Chemical Equation-Symbols and formulas to describe identities and relative molecular/molar amounts of reactants and products HCl + Mg(OH) 2 -> MgCl 2 + H 2 O.
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Chapter 8 Chemical Equations and Reactions
Chemical Reactions • Chemical Reaction- one or more substances are changed • Chemical Equation-Symbols and formulas to describe identities and relative molecular/molar amounts of reactants and products • HCl + Mg(OH)2 -> MgCl2 + H2O
How to know if Reaction occurred • Energy given off (heat/light) • Gas formed (bubbles) • Precipitate formed (2 liquids make undissolvable solid) • Color change (not dilution) • Examples
More on Chemical Equations • Methane + oxygen -> carbon dioxide + water (word equation) • CH4 + O2 -> CO2 + H2O (formula equation) • Formula equations must be balanced • See examples on board
Equation symbols • P. 266 (on board)
Types of reactions • Synthesis • Decomposition • Single Displacement/Metathesis • Double Displacement • Combustion
Synthesis • A + B -> AB • See examples on board
Decomposition • AB -> A + B • Binary • Metal carbonate makes metal oxide and carbon dioxide • Metal hydroxide makes metal oxide and water • Metal chlorate makes metal chloride and oxygen • Acid (sulfuric and carbonic examples) • See examples on board
Single Displacement • A + BC -> AC + B • Or, A + BC -> BA + C • See examples on board • How to know if switch? Activity series (p. 286- water flows down, not up)(ranked according to “popularity”)
Double Displacement • AB + CD-> AD + CB • Keep left on left and right on right • See examples on board
Combustion • Always has oxygen gas as reactant • Striking matches example • If hydrocarbon is involved, get carbon dioxide and water • See examples on board