1. Types of Reactions

2. Synthesis (Combination) Decomposition Single Displacement Double Displacement Combustion Oxidation-Reduction (Redox)

3. Synthesis In a synthesis reaction, two substances react to form one new substance. A + B  AB A and B can be either an element or a compound 2 Na + Cl 2  2 NaCl CaO + CO 2  CaCO 3

4. Decomposition In a decomposition reaction, one compound breaks down into two or more simple substances. AB  A + B 2 HgO  2 Hg + O 2 2 KClO 3  2 KCl + 3 O 2

5. Single Displacement In a single displacement reaction, an uncombined element replaces another element in a compound. Metals replace metals and nonmetals replace nonmetals. The uncombined element must be more chemically reactive than the element it is replacing in order for the reaction to occur. A + BC  B + AC

6. Examples of Single Displacement Reactions Zn + CuSO 4  Cu + ZnSO 4 Cl 2 + 2 NaBr  2 NaCl + Br 2 Na + H 2 O  NaOH + H 2

7. Double Displacement In a double displacement reaction, the positive and negative ions “change partners” and form two new compounds. Three types of products may result: a weak/nonelectrolyte, a precipitate, or a gas. AB + CD  AD + CB

8. Formation of a Weak/Nonelectrolyte HCl + NaOH  NaCl + H 2 O The above reaction is also referred to as a neutralization reaction. Neutralization reactions involve the reaction of an acid and base to produce a salt and water.

9. Formation of a Precipitate AgNO 3 + NaCl  AgCl + NaNO 3 The AgCl is an insoluble salt and will precipitate out of the solution.

10. Formation of a Gas 2HCl + CaCO 3  CaCl 2 + H 2 CO 3 The H 2 CO 3 decomposes to H 2 O and CO 2. 2HCl + CaCO 3  CaCl 2 + H 2 O + CO 2 Another example MnS + 2HCl  MnCl 2 + H 2 S

11. Combustion In a combustion reaction, a hydrocarbon reacts with oxygen to produce carbon dioxide and water. C x H y + O 2  CO 2 + H 2 O

12. Oxidation-Reduction (Redox) Reactions Oxidation-reduction reactions are those that involve the transfer of one or more electrons. All of the previous types of reactions except double displacement are also examples of redox reactions.

13. Oxidation States Oxidation states (or oxidation numbers) are a way to keep track of electrons in redox reactions. Oxidation states are obtained in covalent molecules by arbitrarily assigning the electrons to particular atoms. Actual charges on ions are written as n + or n - while oxidation states (not actual charges) are written as +n or -n.

14. Rules for Assigning Oxidation States The oxidation state of an atom in an element is 0. The oxidation state of a monatomic ion is the same as its charge. In compounds, fluorine is always -1. Oxygen is usually -2. Hydrogen is +1 if combined with nonmetals. The sum of the oxidation states in a neutral compound must be zero. The sum of the oxidation states in an ion must equal the charge on the ion.

15. Assigning Oxidation States Assign the oxidation states to all atoms in the following (Note: Check answers on following slide) CO 2 CO SF 6 Na 2 S 2 O 3 NO 3 - HAsO 2 KMnO 4 XeOF 4 P 4 O 6 Na 2 C 2 O 4

16. Answers C=+4, O=-2 S=+6, F=-1 N=+5, O=-2 K=+1, Mn=+7, O=-2 P=+3, O=-2 C=+2, O=-2 Na=+1, S=+2, O=-2 H=+1, As=+3, O=-2 Xe=+6, O=-2, F=-1 Na=+1, C=+3, O=-2

17. Characteristics of Oxidation-Reduction Reactions Redox reactions are characterized by a transfer of electrons Oxidation is an increase in oxidation state or a loss of electrons. Reduction is a decrease in oxidation state or a gain of electrons. OIL RIG Oxidation is loss; Reduction is gain

18. Characteristics of Oxidation-Reduction Reactions (continued) The oxidizing agent is the electron acceptor and consequently undergoes reduction. The reducing agent is the electron donor and consequently undergoes oxidation.

19. Identifying Oxidizing and Reducing Agents. Identify the oxidizing agent, reducing agent, the species oxidized, and the species reduced for each of the following: a)2AgNO 3 + Cu  Cu(NO 3 ) 2 + 2Ag b)4KClO 3 (s)  KCl(s) + 3KClO 4 (s) c)3AgNO 3(aq) + K 3 PO 4(aq)  Ag 3 PO 4(s) + 3KNO 3(aq)