Type of Reactions Chemical reactions are classified into several general types Combination (Synthesis) Decomposition Single Replacement Double Replacement (Metathesis) 1

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 2

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

Learning Check R1 Classify the following reactions as 1) combination 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 4

Solution R1 Classify the following reactions as 1) combination 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 5

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 6

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 7

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 8

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 9

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 10

Learning Check R3 Balance the combustion equation ___C 5 H 12 + ___O 2 ___CO 2 + ___H 2 O 11

Solution R3 Balance the combustion equation 1 C 5 H O 2 5 CO H 2 O 12

Oxidation and Reduction  Reactions that involve a loss or gain of electrons  Occurs in many of the types of reactions and combustion  Important in food metabolism, batteries, rusting of metals 13

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 14

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 15

Learning Check R3 Identify the following as an 1) oxidation or a reduction process: __A. SnSn e- __B. Fe e - Fe 2+ __C. Cl 2 + 2e - 2Cl - 16

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 - 17

Redox Redox REDOX stands for REDuction/OXidation Oxidation refers to a loss of electrons Reduction refers to a gain of electrons LEO –GER Loss Electrons = Oxidation Gain Electrons = Reduction OIL-RIG Oxidation Is Loss Reduction Is Gain 18

oxidation = loss of e – X  X + + e – reduction = gain of e – X + e –  X – 19

Oxidation numbers We will see that there is a simple way to keep track of oxidation and reduction This is done via “oxidation numbers” An oxidation number is the charge an atom would have if electrons in its bonds belonged completely to the more electronegative atom 20

Rules 1.Any element, when not combined with atoms of a different element, has an oxidation # of zero. (O in O 2 is zero) 2.Any simple monatomic ion (one-atom ion) has an oxidation number equal to its charge (Na + is +1, O 2– is –2) 3.The sum of the oxidation numbers of all of the atoms in a formula must equal the charge written for the formula. (if the oxidation number of O is –2, then in CO 3 2– the oxidation number of C is +4) 21

4.In compounds, the oxidation # of IA metals is +1, IIA is +2, and aluminum (in IIIA) is +3 5.In ionic compounds, the oxidation # of a nonmetal or polyatomic ion is equal to the charge of its associated ion. (CuCl 2, Cl is –1) 6.F is always –1, O is always –2 (unless combined with F), H is usually +1 total Ox.#Rules H N O 3H N O 3 C2H6OC2H6O K 2 Cr 2 O 7 AgI H 2 PO 4 – 22

Writing Chemical Equations

Classifying Reactions –Combination Reactions A combination reaction is a chemical change in which two or more substances react to form a single new substance

Classifying Reactions –Decomposition Reactions A decomposition reaction is a chemical change in which a single compound breaks down into two or more simpler products

Classifying Reactions –Single-Replacement Reactions A single-replacement reaction is a chemical change in which one element replaces a second element in a compound

Classifying Reactions The activity series of metals lists metals in order of decreasing reactivity. Generally, the higher in the periodic table, the more reactive

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Classifying Reactions –Double-Replacement Reactions A double-replacement reaction is a chemical change involving an exchange of positive ions between two compounds

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Predicting the Formation of a Precipitate

Classifying Reactions –Combustion Reactions A combustion reaction is a chemical change in which an element or a compound reacts with oxygen, often producing energy in the form of heat and light

Net Ionic Equations A complete ionic equation is an equation that shows dissolved ionic compounds as dissociated free ions

Net Ionic Equations An ion that appears on both sides of an equation and is not directly involved in the reaction is called a spectator ion. The net ionic equation is an equation for a reaction in solution that shows only those particles that are directly involved in the chemical change

Net Ionic Equations –A net ionic equation shows only those particles involved in the reaction and is balanced with respect to both mass and charge

Net Ionic Equations Sodium ions and nitrate ions are not changed during the chemical reaction of silver nitrate and sodium chloride so the net ionic equation is

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Will a precipitate form when a sodium carbonate solution is mixed with a barium nitrate solution?

Predicting the Formation of a Precipitate Sodium nitrate is soluble but barium carbonate is insoluble. The net ionic equation is