Types of Reactions

Chemical Equation Reminders When not part of a compound, diatomic elements are written as: H2 O2 F2 Br2 I2 N2 Cl2 Charges in a compound formula MUST cancel out to zero—i.e. the valance electrons must work out. When balancing the overall equation, you can only change the COEFFICIENTS

Synthesis Reactions A + B → AB How do you tell? In a synthesis reaction, two or more substances combine to form a new compound. A + B → AB How do you tell? element + element → compound

Predicting the Products of Synthesis Reactions Write compound formulas so charges cancel out! Don’t worry about balancing the overall equation for now! Na + Cl2  Na + Cl2  NaCl Al + S  Al + S  Al2S3

Decomposition Reaction In a decomposition reaction a single compound is broken down to form two or more smaller compounds. AB → A + B How do you tell? Compound → element + element

Predicting the Products of Decomposition Reactions Write compound formulas so charges cancel out! Don’t worry about balancing the overall equation for now! NH3  NH3  N2 + H2 CaF CaF  Ca + F2

Combustion Reaction Carbon compound + O2 → CO2 + H2O In a combustion reaction (burning), a carbon compound combines with oxygen and releases a large amount of energy in the form of light and heat. Carbon compound + O2 → CO2 + H2O The products of a combustion reaction are ALWAYS CO2 + H2O

Predicting the Products of Combustion Reactions Write compound formulas so charges cancel out! Don’t worry about balancing the overall equation for now! CH4 + O2  CH4 + O2  CO2 + H2O C2H8 + O2  C2H8 + O2  CO2 + H2O

Types of Reactions Practice Identify the following unbalanced reactions as synthesis, decomposition, or combustion. EXPLAIN YOUR CHOICE. 1. C10H22 + O2 → CO2 + H2O 2. MgO → Mg + O2 3. PCl3 + Cl2 → PCl5

Single Replacement Reaction In a single replacement reaction, one element replaces a similar element in a compound. A + BX → AX + B How do you tell? element + compound → element + compound

Predicting the Products of Single Replacement Reactions Write compound formulas so charges cancel out! Don’t worry about balancing the overall equation for now! K + CuSO4  K + CuSO4  K2SO4 + Cu Cl2 + NaBr  Cl2 + NaBr  NaCl + Br2

Double Replacement Reaction In a double replacement reaction, ions from two compounds in solution exchange places to produce two new compounds. AB + CD → AD + CB NaCl + AgNO3  AgCl + NaNO3 How do you tell? compound + compound → compound + compound

Predicting the Products of Double Replacement Reactions Write compound formulas so charges cancel out! Don’t worry about balancing the overall equation for now! Na2S + HCl  Na2S + HCl  NaCl + H2S Ca(NO3)2 + NaCl  Ca(NO3)2 + NaCl  NaNO3 + CaCl2

Types of Reactions Practice Identify the following unbalanced reactions as synthesis, decomposition, single displacement, or double displacement. EXPLAIN YOUR CHOICE. 1. KOH + HBr → KBr + H2O 2. Mg + CO2 → MgO + C 3. PCl3 + Cl2 → PCl5

Carbon compound + O2 → CO2 + H2O Type of Reaction Identifying the type… General Equation two or more reactants combine to produce ONE compound A + B → AB Synthesis + → ONE compound is broken down to produce two or more compounds AB → A + B Decomposition → + element + compound produces element + compound A + BX → AX + B Single Displacement + → + two compounds produce two compounds AB + CD → AD + BC Double Displacement + → + burning - carbon compound combines with oxygen to release heat/energy Carbon compound + O2 → CO2 + H2O Combustion ALWAYS THE PRODUCTS!

Types of Reaction Examples Synthesis: Mg + O2  MgO Decomposition: KBrO3  KBr + O2 Single Displacement: Fe + CuSO4  Cu + FeSO4 Double Displacement: NaCl + AgNO3  AgCl + NaNO3 Combustion: C6H14 + O2 → CO2 + H2O