Chapter 4 Aqueous Reactions and Solution Stoichiometry

1. Chemistry, The Central Science, 10th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten Chapter 4Aqueous Reactions and Solution Stoichiometry John D. Bookstaver St. Charles Community College St. Peters, MO  2006, Prentice Hall, Inc.

2. Solutions: • Homogeneous mixtures of two or more pure substances. • The _____ is present in greatest abundance. • All other substances are _____.

3. Dissociation • When an ionic substance dissolves in water, the solvent pulls the individual ions from the crystal and solvates them. • This process is called _____.

4. Electrolytes • Substances that dissociate into ions when dissolved in water. Example: • A_____ may dissolve in water, but it does not dissociate into ions when it does so. Example:

5. Electrolytes and Nonelectrolytes ______________________________ tend to be electrolytes.

6. Electrolytes and Nonelectrolytes ________________ tend to be nonelectrolytes, except for _____ and _____.

7. SAMPLE EXERCISE 4.1 Relating Relative Numbers of Anions and Cations to Chemical Formulas The diagram below represents an aqueous solution of one of the following compounds: MgCl2 , KCl, or K2SO4. Which solution does it best represent?

8. Electrolytes • A strong electrolyte dissociates ____________________________________ • A weak electrolyte only dissociates ____________________________________

9. Strong Electrolytes Are… • Strong acids • Strong bases • Soluble ionic salts

10. Precipitation Reactions When one mixes ions that form compounds that are insoluble (as could be predicted by the solubility guidelines), a precipitate is formed.

11. Metathesis comes from a Greek word that means ______________ AgNO3 (aq) + KCl (aq)  AgCl (s) + KNO3 (aq) Metathesis (Exchange) Reactionsa.k.a. Double Replacement Rxns

12. Metathesis comes from a Greek word that means __________ It appears the ions in the reactant compounds __________________________ AgNO3 (aq) + KCl (aq)  Metathesis (Exchange) Reactions

13. AgNO3 (aq) + KCl (aq)  How did we know that silver chloride was a solid??? We checked the ____________________.

15. Predict the products of the following reactions • BaCl2(aq) + K2SO4(aq) • Fe2(SO4)3(aq) + LiOH (aq) • Mg(NO3)2(aq) + CaS (aq) • NaCl (aq) + KNO3(aq)

16. Solution Chemistry • It is helpful to pay attention to exactly what species are present in a reaction mixture (i.e., solid, liquid, gas, aqueous solution). • If we are to understand reactivity, we must be aware of just what is changing during the course of a reaction.

17. The _______________ equation lists the reactants and products in their molecular form. AgNO3 (aq) + KCl(aq) AgCl(s) + KNO3 (aq) Molecular Equation

18. In the ionic equation all __________________ (strong acids, strong bases, and soluble ionic salts) are _______________ into their ___________. This _______________ reflects the species that are found in the reaction mixture. Ag+(aq) + NO3- (aq) + K+ (aq) + Cl- (aq)  AgCl(s) + K+(aq) + NO3- (aq) Ionic Equation

19. To form the _____ ionic equation, __________ anything that does not change from the left side of the equation to the right. Ag+(aq) + NO3-(aq) + K+(aq) + Cl-(aq) AgCl(s) + K+(aq) + NO3-(aq) Net Ionic Equation

20. To form the net ionic equation, cross out anything that does not change from the left side of the equation to the right. The only things left in the equation are _______________________ (i.e., react) during the course of the reaction. Ag+(aq) + Cl-(aq) AgCl(s) Net Ionic Equation

21. To form the net ionic equation, cross out anything that does not change from the left side of the equation to the right. The only things left in the equation are those things that change (i.e., react) during the course of the reaction. Those things that didn’t change (and were deleted from the net ionic equation) are called ___________. Ag+(aq) + NO3-(aq) + K+(aq) + Cl-(aq) AgCl(s) + K+(aq) + NO3-(aq) Net Ionic Equation

22. Writing Net Ionic Equations • Write a • Dissociate all • Cross out anything that remains unchanged from the left side to the right side of the equation. • Write the net ionic equation with the species that remain.

23. Writing Net Ionic Equations Write the net ionic equation for each reaction • Pb(NO3)2(aq) + KI (aq) • Li2S (aq) + BaBr2(aq) • NH4Cl (aq) + Sr(OH)2(aq)

24. Acids: • Substances that increase the concentration of H+ when dissolved in water (__________). • Proton donors (________________).

25. Acids There are only seven strong acids: • Hydrochloric (HCl) • Hydrobromic (HBr) • Hydroiodic (HI) • Nitric (HNO3) • Sulfuric (H2SO4) • Chloric (HClO3) • Perchloric (HClO4)

26. Bases: • Substances that increase the concentration of OH− when dissolved in water (________). • Proton acceptors (______________).

27. Bases The strong bases are the soluble salts of hydroxide ion:

28. Acid-Base Reactions In an acid-base reaction, _____ donates a proton (H+) to the _____.

29. Generally, when solutions of an acid and a base are combined, the products are ____________________. HCl (aq) + NaOH (aq)  NaCl (aq) + H2O (l) Neutralization Reactions

30. When a strong acid reacts with a strong base, the net ionic equation is… HCl (aq) + NaOH (aq)  NaCl (aq) + H2O (l) H+ (aq)+ Cl- (aq)+ Na+ (aq) + OH-(aq) Na+ (aq)+ Cl- (aq)+ H2O (l) Neutralization Reactions

31. When a strong acid reacts with a strong base, the net ionic equation is… HCl (aq) + NaOH (aq)  NaCl (aq) + H2O (l) H+ (aq)+ Cl- (aq)+ Na+ (aq) + OH-(aq) Na+ (aq)+ Cl- (aq)+ H2O (l) H+ (aq)+ Cl- (aq)+ Na+ (aq) + OH- (aq) Na+ (aq) + Cl- (aq) + H2O (l) Neutralization Reactions H+ (aq) + OH- (aq) → H2O (l)

32. Neutralization ReactionsWhat does this have to do with you??? What happens when you have a stomach ache? What do you do about it? Why?

33. Neutralization ReactionsWhat does this have to do with you??? Many antacids contain magnesium hydroxide. It undergoes a neutralization reaction with stomach acid. What acid constitutes the largest quantity of stomach acid? Write a net ionic equation for the neutralization reaction between magnesium hydroxide and hydrochloric acid. Mg(OH)2 (s) + H+(aq)→ Mg2+(aq) + H2O (l)

34. Neutralization Reactions Observe the reaction between Milk of Magnesia, Mg(OH)2, and HCl. Can you overdoes on antacid?? What do you think would happen?

35. These metathesis reactions do not give the _______________________. The __________________ decomposes to give a gaseous product ( ). CaCO3 (s) + HCl (aq) CaCl2 (aq) + CO2 (g) + H2O (l) NaHCO3 (aq) + HBr (aq) NaBr (aq)+ CO2 (g) + H2O (l) SrSO3 (s) + 2 HI(aq) SrI2 (aq) + SO2 (g) + H2O (l) Gas-Forming Reactions

36. This reaction gives the predicted product, but you had better carry it out in the hood, or you will be very unpopular! Just as in the previous examples, a gas is formed as a product of this reaction: Na2S (aq) + H2SO4 (aq) Na2SO4 (aq) + H2S (g) Gas-Forming Reactions

37. A Carbonated Beverage is Another Example How is a beverage carbonated? What happens to the dissolved gas? H2O (l) + CO2(g)↔ H2CO3(aq) H2O (l) + CO2(g)↔ 2H+ (aq) + CO3-2(aq)

38. Oxidation-Reduction Reactions • An _______ occurs when an atom or ion loses electrons. • A _______ occurs when an atom or ion gains electrons.

39. Oxidation-Reduction Reactions

40. Oxidation Numbers To determine if an oxidation-reduction reaction has occurred, we assign an _________________ to each element in a neutral compound or charged entity.

41. Oxidation Numbers • Elements in their elemental form have an oxidation number of _____. • The oxidation number of a monatomic ion is ___________________.

42. Oxidation Numbers • Nonmetals tend to have negative oxidation numbers, ______________________________________________________________. • Oxygen has an oxidation number of −2, except in the peroxide ion in which it has an oxidation number of −1. • Hydrogen is −1 when bonded to a metal, +1 when bonded to a nonmetal.

43. Oxidation Numbers • Nonmetals tend to have negative oxidation numbers, although some are positive in certain compounds or ions. • Fluorine always has an oxidation number of −1. • The other halogens have an oxidation number of −1 when they are negative; they can have positive oxidation numbers, however, most notably in oxyanions.

44. Oxidation Numbers • The sum of the oxidation numbers in a neutral compound is 0. • The sum of the oxidation numbers in a polyatomic ion is the _________________.

45. Oxidation NumbersFind the oxidation numbers for each of the following species. • CO32- • H2S • S8 • SCl2 • SO42- • Cr2O72-

46. Displacement Reactions • In displacement reactions, ions ________________. • The ions, then, are reduced.

47. Displacement Reactions In this reaction, silver ions ________ copper metal. Cu (s) + 2 Ag+ (aq) Cu2+ (aq) + 2 Ag (s)

48. Displacement Reactions The reverse reaction, however, does not occur. Cu2+ (aq) + 2 Ag (s)  Cu (s) + 2 Ag+ (aq) x

49. Activity Series

50. Use the Activity Series to predict the products of the following reactions. If the reactions does take place, write the net ionic equation for the reaction. Lastly, identify the species being oxidized and reduced. • Al (s) + HBr (aq) • Fe(s) + KI (aq) • Zn (s) + Ni(NO3)2(aq)