1. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 1 Predicting Whether a Reaction Will Occur “Forces” that drive a reaction: Formation of a solid Formation of water Transfer of electrons Formation of a gas When chemicals (dissolved in water) are mixed and one of these four things can occur, the reaction will generally happen.

2. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 2 Dissociation Ionic compounds –Metal + nonmetal (Type I & II) –Metal + polyatomic anion –Polyatomic cation + anion Dissociation: When ionic compounds dissolve in water the anions and cations are separated from each other. We know that ionic compounds dissociate when they dissolve in water because the solution conducts electricity.

3. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 3 Dissociation (cont.) Potassium chloride dissociates in water into potassium cations and chloride anions. KCl(aq) = K + (aq) + Cl - (aq) Copper(II) sulfate dissociates in water into copper(II) cations and sulfate anions. CuSO 4 (aq) = Cu +2 (aq) + SO 4 2- (aq) K+K+ Cl - K Cl Cu +2 SO 4 2- Cu SO 4

4. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 4 Precipitation Reactions In all precipitation reactions, the ions of one substance are exchanged with the ions of another substance when their aqueous solutions are mixed. At least one of the products formed is insoluble in water. KI(aq) + AgNO 3 (aq)  KNO 3 (aq) + AgI  s  K+K+ I-I- Ag + NO 3 - K+K+ Ag I

5. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 5 Process for Predicting the Products of a Precipitation Reaction Determine what ions each aqueous reactant has. Exchange ions. –(+) ion from one reactant with (-) ion from other Balance charges of combined ions to get formula of each product. Balance the equation. –Count atoms. Determine solubility of each product in water. –Use solubility rules. –If product is insoluble or slightly soluble, it will precipitate.

6. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 6 Solubility Rules Most compounds that contain NO 3 - ions are soluble. Most compounds that contain Na +, K +, or NH 4 + ions are soluble. Most compounds that contain Cl - ions are soluble, except AgCl, PbCl 2, and Hg 2 Cl 2 Most compounds that contain SO 4 2- ions are soluble, except BaSO 4, PbSO 4, CaSO 4

7. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 7 Solubility Rules (cont.) Most compounds that contain OH - ions are slightly soluble (will precipitate), except NaOH and KOH, which are soluble, and Ba(OH) 2, Ca(OH) 2, which are moderately soluble. Most compounds that contain S 2-, CO 3 2-, or PO 4 3- ions are slightly soluble (will precipitate).

8. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 8 Predict what will happen when the following solutions are mixed: AgNO 3 (aq) and NH 4 Cl(aq) Na 3 PO 4 (aq) and Co(NO 2 ) 2 (aq) K 2 CrO 4 (aq) and Pb(C 2 H 3 O 2 ) 2 (aq)

9. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 9 Describing Reactions in Aqueous Solutions Molecular equations: equations that show the complete formulas of all reactants and products Example: Ionic equations: All substances that are strong electrolytes are represented as ions. Solids are not written as separate ions. Example:

10. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 10 Describing Reactions in Aqueous Solutions (cont.) Spectator ions: ions that do not participate in the reaction Example: Net ionic equation: Only the components directly involved the reaction are written. Example:

11. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 11 Write molecular, complete ionic, and net ionic equations for the following reaction: nickel(II) sulfate and barium chloride

12. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 12 Write molecular, complete ionic, and net ionic equations for the following reaction: iron(III) nitrate and sodium hydroxide

13. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 13 Reactions that Form Water: Acids and Bases When acids dissociate in water they release H + ions and their anions. When bases dissociate in water they release or form OH - ions and their cations.

14. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 14 Acid-Base Reactions In the reaction of an acid with a base, the H + from the acid combines with the OH - from the base to make water. The cation from the base combines with the anion from the acid to make the salt. acid + base  salt + water H 2 SO 4 (aq) + Ca(OH) 2 (aq)  CaSO 4 (aq) + 2 H 2 O(l) The net ionic equation for a strong acid-strong base reaction is always: H + (aq) + OH - (aq)  H 2 O(l)

15. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 15 Erucic Acid (a weak acid from marsh marigold)

16. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 16 Complete the following acid-base reactions: HCl(aq) + RbOH(aq) → HNO 3 (aq) + LiOH(aq) →

17. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 17 Oxidation-Reduction Reactions Oxidation-reduction reactions: reactions that involve a transfer of one or more electrons The substance that loses electrons in the reaction is oxidized. The substance that gains electrons in the reaction is reduced.

18. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 18 Reactions of Metals with Nonmetals (Oxidation-Reduction) The metal loses electrons and becomes a cation (oxidation) The nonmetal gains electrons and becomes an anion (reduction) In the reaction, electrons are transferred from the metal to the nonmetal. 2K(s) + F 2 (g) → 2KF(s) metal nonmetal

19. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 19

20. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 20 Characteristics of Oxidation-Reduction Reactions Metal + nonmetal  ionic compound (solid) In the ionic compound the metal is now a cation and the nonmetal is an anion. Two nonmetals can undergo an oxidation-reduction reaction. Look for O 2 as a reactant or product. In this case the products are not ionic. Examples:

21. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 21 Ways to Classify Reactions Precipitation reactions: reactions that involve solid formation. Example: Double displacement reactions: ion exchange reactions AB + CD → AD + CB Example: Acid-base reactions: reactions that involve water formation Example: Both precipitation reactions and acid-base reactions involve compounds exchanging ions.

22. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 22 Ways to Classify Reactions (cont.) Oxidation-reduction reactions: reactions that involve electron transfer Example: Also classified as a single displacement reaction: A + BC → B + AC Combustion reactions: reactions in which O 2 (g) is reacted with a carbon compound –Release a lot of energy –Subclass of oxidation-reduction reactions –Example:

23. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 23 Other Ways to Classify Reactions Synthesis reactions: reactions in which chemicals combine to make one product –Metal + nonmetal reactions can be classified as synthesis reactions. Example: –Reactions of metals or monmetals with O 2 can be classified as synthesis reactions. Example: These two types of synthesis reactions are also subclasses of oxidation-reduction reactions.

24. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 24 Other Ways to Classify Reactions Decomposition reactions: reactions in which one reactant breaks down into simpler compounds or elements Generally initiated by addition of electric current or heat Example: Opposite of a synthesis reaction

25. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 25 Summary of Classes of Reactions

26. Copyright © Houghton Mifflin Company. All rights reserved. 7 | 26 Classify the following reactions in as many ways as possible: C(s) + O 2 (g) → CO 2 (g) Zn(s) + 2HBr(aq) → H 2 (g) + ZnBr(aq) 2KClO 3 (s) → 2KCl(s) + 3O 2 (g) H 2 SO 4 (aq) + Ba(OH) 2 (aq) → 2H 2 O(l) + BaSO 4 (s)