Types of Reactions

Type of Reactions Chemical reactions are classified into four general types Synthesis (aka Combination) Decomposition Single Replacement Double Replacement

Combination (Synthesis) Two or more elements or simple compounds combine to form (synthesize) one product A + B AB 2Mg + O 2 2MgO 2Na + Cl 2 2NaCl SO 3 + H 2 OH 2 SO 4

Decomposition One substance is broken down (split) into two or more simpler substances. ABA + B 2HgO2Hg + O 2 2KClO 3 2KCl + 3 O 2

Learning Check R1 Classify the following reactions as 1) synthesis or 2) decomposition: ___A. H 2 + Br 2 2HBr ___B. Al 2 (CO 3 ) 3 Al 2 O 3 + 3CO 2 ___C. 4 Al + 3C Al 4 C 3

Solution R1 Classify the following reactions as 1) synthesis or 2) decomposition: _1_A. H 2 + Br 2 2HBr _2_B. Al 2 (CO 3 ) 3 Al 2 O 3 + 3CO 2 _1_C. 4 Al + 3C Al 4 C 3

Single Replacement One element takes the place of an element in a reacting compound. A + BC AB + C Zn + 2HCl ZnCl 2 + H 2 Fe + CuSO 4 FeSO 4 +Cu

Double Replacement Two elements in reactants take the place of each other AB + CD AD + CB AgNO 3 + NaCl AgCl + NaNO 3 ZnS + 2HCl ZnCl 2 +H 2 S

Learning Check R2 Classify the following reactions as 1) single replacement 2) double replacement __ A. 2Al + 3H 2 SO 4 Al 2 (SO 4 ) 3 + 3H 2 __B. Na 2 SO 4 + 2AgNO 3 Ag 2 SO 4 + 2NaNO 3 __C. 3C + Fe 2 O 3 2Fe + 3CO

Solution R2 Classify the following reactions as 1) single replacement 2) double replacement 1_ A. 2Al + 3H 2 SO 4 Al 2 (SO 4 ) 3 + 3H 2 2_B. Na 2 SO 4 + 2AgNO 3 Ag 2 SO 4 + 2NaNO 3 1_C. 3C + Fe 2 O 3 2Fe + 3CO

Combustion A reaction in which a compound (often carbon) reacts with oxygen C + O 2 CO 2 CH 4 + 2O 2 CO 2 + 2H 2 O C 3 H 8 + 5O 2 3CO 2 + 4H 2 O C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O

Learning Check R3 Balance the combustion equation ___C 5 H 12 + ___O 2 ___CO 2 + ___H 2 O

Solution R3 Balance the combustion equation 1 C 5 H O 2 5 CO H 2 O

Oxidation and Reduction  Reactions that involve a loss or gain of electrons  Occurs in many of the 4 types of reactions and combustion  Important in food metabolism, batteries, rusting of metals

Requirements for Oxidization- Reduction Electrons are transferred Two processes occur Oxidation = Loss of electrons (LEO) ZnZn e - Reduction = Gain of electrons (GER) Cu e - Cu

Balanced Red-Ox Equations Combine the oxidation and reduction reactions to make Loss of electrons = Gain of electrons Zn + Cu e - Zn e - + Cu Zn + Cu 2+ Zn 2+ + Cu

Gain/Loss of Hydrogen In organic and biological reactions oxidation = Loss of H reduction = Gain of H

Learning Check R3 Identify the following as an 1) oxidation or 2) a reduction process: __A. SnSn e- __B. Fe e - Fe 2+ __C. Cl 2 + 2e - 2Cl -

Solution R3 Identify the following as an 1) oxidation or a reduction process: 1_ A. SnSn e- 2_ B. Fe e - Fe 2+ 2_ C. Cl 2 + 2e - 2Cl -

Learning Check R4 In light-sensitive sunglasses, UV light initiates an oxidation-reduction reaction Ag + + Cl - Ag + Cl A. Which reactant is oxidized 1) Ag + 2) Cl - 3) Ag B. Which reactant is reduced? 1) Ag + 2) Cl - 3) Cl

Solution R4 In light-sensitive sunglasses, UV light initiates an oxidation-reduction reaction Ag + + Cl - Ag + Cl A. Which reactant is oxidized 2) Cl - Cl - Cl + e - B. Which reactant is reduced? 1) Ag + Ag + + e- Ag

Acid-Base reactions A special kind of double displacement reaction that takes place when an acid and base react with each other. The H + ion in the acid reacts with the OH - ion in the base, causing the formation of water. The product of this reaction is some ionic salt and water: HA + BOH ---> H 2 O + BA Example : HBr + NaOH ---> NaBr + H 2 O

1) Does your reaction have oxygen as one of it's reactants and carbon dioxide and water as products? If yes, then it's a combustion reaction 2) Does your reaction have two (or more) chemicals combining to form one chemical? If yes, then it's a synthesis reaction 3) Does your reaction have one large molecule falling apart to make several small ones? If yes, then it's a decomposition reaction 4) Does your reaction have any molecules that contain only one element? If yes, then it's a single displacement reaction 5) Does your reaction have water as one of the products? If yes, then it's an acid-base reaction 6) If you haven't answered "yes" to any of the questions above, then you've got a double displacement reaction

Identify the type of reactions shown below: 1) NaOH + KNO 3 --> NaNO 3 + KOH 2) CH O 2 --> CO H 2 O 3) 2 Fe + 6 NaBr --> 2 FeBr Na 4) CaSO 4 + Mg(OH) 2 --> Ca(OH) 2 + MgSO 4 5) NH 4 OH + HBr --> H 2 O + NH 4 Br 6) Pb + O 2 --> PbO 2 7) Na 2 CO 3 --> Na 2 O + CO 2

Solutions to the Sample Problems 1) double displacement 2) combustion 3) single displacement 4) double displacement 5) acid-base 6) synthesis 7) decomposition

pH scale