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9-3: Classifying Chemical Reactions. By Ms. Pacheco. Direct Combination Rxns. Two or more elements or compounds combine to form a new compound A + B AB A and B can be elements or cmpds AB is a cmpd Ex: Na + Cl 2 NaCl Also known as “synthesis rxns”.
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9-3: Classifying Chemical Reactions By Ms. Pacheco
Direct Combination Rxns • Two or more elements or compounds combine to form a new compound • A + B AB • A and B can be elements or cmpds • AB is a cmpd • Ex: Na + Cl2 NaCl • Also known as “synthesis rxns”
Decomposition Reactions • A compound breaks down into two or more elements or compounds • AB A + B • Ex: H2O H2 + O2 • Opposite of direct comb. rxn • 2NaCl 2Na + Cl2
Single Replacement Reactions • An uncombined element displaces an element that is part of a compound • A + BX AX + B • Ex: Mg + CuSO4 Cu + MgSO4
We can predict whether or not single replacement reactions will occur… • Using the Activity Series of Metals (pg. 295) • The higher up on the table the metal is, the more reactive • Therefore, it will replace any metal underneath
For example: Will the following reaction occur? • Ca + MgSO4 CaSO4 + Mg • Yes, because calcium is more active than magnesium and will replace it as the equation shows
Double Replacement Reactions • Atoms or ions from two different compounds replace each other • AX + BY AY + BX • Ex: CaCO3 + HCl CaCl2 + H2CO3
Some reactions do not fit into any of the four main categories • Combustion reactions: • When any thing is burned in the presence of oxygen to produce carbon dioxide and water • Ex: (the combustion of propane) C3H8 + O2 CO2 + H2O