1. Reactions in Aqueous Solutions Chapter 4

2. Objectives 2.0 Define key terms and concepts. 2.6 Calculate the concentration of a solution. 2.7 Determine if a compound is an electrolyte. 2.8 Prepare a dilute solution from a more concentrated solution. 2.9 Predict the products for basic chemical reactions. 2.10 Predict if a precipitate will form in a reaction. 2.11 Write the net ionic equation for a reaction. 2.12 Determine the amount of a compound present in solution by using gravimetric or volumetric analysis.

3. Solutions Solution ▫Homogeneous mixture of two or more substances Solute ▫What is dissolved ▫Present in the smaller quantity Solvent ▫What does the dissolving ▫Present in the greater quantity Solubility ▫The maximum amount of solute that will dissolve in a given quantity of solvent at a specific temperature

4. Solutions

5. Solubility Unsaturated Solution ▫When the solution does not contain the maximum amount of solute Saturated Solution ▫When the solution contains the maximum amount of solute ▫Undissolved solute remains on the bottom of the solution

6. Solutions Aqueous Solution ▫Solution in which water is the solvent Dilute Solution ▫Solution that contains a little bit of solute and a lot of solvent ▫Saline Solution Concentrated Solution ▫Solution that contains a lot of solute and little solvent ▫Laundry Detergent

7. Solubility As the temperature of a solution increases, its solubility increases. The solubility of a gas decreases with increased temperature The solubility of a gas increases with increased pressure

8. Solutions Electrolytes ▫Separate into ions when dissolved in water (ionic compounds and compounds with polyatomic ions) ▫Conducts electricity

9. Solutions Nonelectrolyte ▫Do not separate into ions when dissolved in water ▫Do not conduct electricity

10. Solutions Strong Electrolytes ▫Dissociates completely when it dissolved in water Dissociate ▫When a molecule separates into ions

11. Solutions Hydration ▫When water molecules surround an ion in a specific manner

12. Solutions Weak Electrolytes ▫Solute dissolve in water mostly as whole molecules (does not dissociate) Chemical Equilibrium ▫The point in a chemical reaction where molecules dissociate as fast as they recombine and no net- change can be observed.

13. Solutions Type of SolutesDissociatio n Contained in Solution Conducts Electricity Examples Strong ElectrolytesCompletelyOnly IonsYesIonic Compounds, strong acids and bases Weak ElectrolytePartiallyMostly Molecules with a few ions Yes, but not well Weak acids and bases such as HF, CH 3 OOH, H 2 O, NH 3 NonelectrolyteNoneOnly MoleculesNoCarbon Compounds such as alcohols and sugars

14. Molarity Concentration of a Solution ▫The amount of solute present in a given amount of solvent (or solution) Molarity ▫The amount of solute in moles divided by the amount of solvent measured in Liters ▫Another way to measure concentration ▫Measured in moles per Liter (mol/L) Moles M x V

15. What is the molarity of a solutions containing 4.2 moles of NaOH dissolved in 1.95 L of water?

16. What is the molarity of a solution containing 9.6g of NaCl dissolved in 0.86L of water?

17. Calculate the concentration of a solution containing 15.9g of potassium permanganate dissolved in 300mL of water.

18. To prepare a 0.65M solution of KOH, 10.9grams of the compound are dissolved in a volume of water. What is the amount of water the KOH was dissolved in?

19. A laboratory experiment requires you to prepare a 1.5M solution of NaOH. How many grams of NaOH are required to make 0.75L of this solution?

20. Dilution Making a less concentrated solution from a more concentrated one. M i V i = M f V f What volume of solution would you need to prepare 500mL a 0.35M solution if you started with a 1.2M solution of HCl?

21. If 52mL of a 2.5M KCl solution is diluted to a volume of 500mL, what is the concentration of the new solution? How many grams of KCl are present?

22. You have 107mL of a 0.125M solution of HNO 3 and you want to dilute that entire amount to a 0.075M solution. How much water should you add to the solution?

23. What are your questions?

24. Types of Reactions

25. Complete and balance the following reactions. Zn + S  MgO  Ba + HNO 3  Ag + O 2  Cu 2 O  C 3 H 8 + CO 2 

26. Complete and balance the following reactions. Zn(NO 3 ) 2 + AgI  Zn + AgNO 3  CaCl 2 x 2H 2 O + heat  AgNO 3 + Na 3 PO 4  C 10 H 22 + O 2 

27. Types of Reactions Precipitation ▫When an insoluble solid forms during a reaction Can determine precipitate using solubility rules

28. Solubility Rules Soluble Compounds Almost all salts of Na +, K +, and NH 4 + Salts of NO 3 -, ClO 3 -, ClO 4 -, C 2 H 3 O 2 - Exceptions Almost all salts of Cl -, Br -, I - Halides of Ag +, Hg 2+, Pb 2+ Compounds containing F - Fluorides of Mg 2+, Ca 2+, Sr 2+, Ba 2+, and Pb 2+ Salts of SO 4 2- Sulfates of Ca 2+, Sr 2+, Ba 2+, Pb 2+ Insoluble CompoundsExceptions Most salts of CO 3 2-, PO 4 3-, C 2 O 4 2-, CrO 4 2- Salts of NH 4 + and alkali metal cations Most metal sulfides, S 2- Most metal hydroxides and oxides

29. Net Ionic Equations

30. Write the net ionic equation for the following reaction Pb(NO 3 ) 2 + KI 

31. Write the net ionic equation for the following reaction Ba(NO 3 ) 2 + MgSO 4 →

32. Write the net ionic equation for the following reaction NaOH + H 2 SO 4 

33. Write the net ionic equation for the following reaction HC 2 H 3 O 2 + NaHCO 3 

34. Write the net ionic equation for the following reaction Mg + HCl 

35. What Are your questions?

36. Acid-Base Reactions Acids ▫Have a sour taste ▫Will turn litmus paper red ▫Will conduct electricity when in aqueous solution ▫Reacts with metals such as Zn, Mg, and Fe to produce hydrogen gas 2HCl (aq) + Zn (s)  ZnCl 2(aq) + H 2(g) ▫Will react with carbonates and bicarbonates to produce CO 2 2HCl (aq) + CaCO 3(s)  CaCl 2(aq) + H 2 O (l) + CO 2(g)

37. Acid-Base Reactions Strong Acids ▫Will completely ionize in water H 2 SO 4  H + + HSO 4 - ▫Only a few strong acids  HCl, HNO 3, H 2 SO 4, HBr, HI, HClO 4 Weak Acids ▫Will only partially ionize in water ▫Most acids are weak  HF, acetic acid, citric acid

38. Acid-Base Reactions Bases ▫Have a bitter taste ▫Feel Slippery ▫Turns litmus paper Blue ▫Will conduct electricity when in aqueous solution

39. Acid-Base Reactions Strong Bases ▫Will completely ionize in water NaOH  Na + + OH - ▫The hydroxides of Group I & II metals are considered to be strong bases Weak Bases ▫Weak Bases do not furnish OH - ions by dissociation. Instead, they react with water to generate OH - ions. NH 3 + H 2 O  NH 4 + OH -

40. Bronsted-Lowry Acid-Base Theory Acid ▫Proton Donor ▫HCl + H 2 O  H 3 O + + Cl -

41. Bronsted-Lowry Acid-Base Theory Base ▫Proton Acceptor ▫NH 3 + H 2 O  NH 4 + OH -

42. Acid-Base Reactions Neutralization ▫The reaction between a strong acid and a strong base with produces salt and water ▫Double replacement reaction Salt ▫An ionic compound that does not have H+ or OH- ions

43. Complete the following neutralization reactions. H 2 SO 4 + KOH  HCl + NaOH  H 3 PO 4 + Mg(OH) 2  HNO 3 + Ca(OH) 2  HBr + Sr(OH) 2 

44. Acid-Base Reactions Some acid-base reactions will also produce a gas. These usually involve a carbonate, bicarbonate, sulfite, or sulfide Na 2 CO 3 + 2HCl  2NaCl + H 2 CO 3 NaHCO 3 + HNO 3  NaNO 3 + H 2 O + CO 2 K 2 S + 2HBr  2KBr + H 2 S

45. Redox Reactions Involve the gain and lose of electrons by chemicals in a reaction Oxidation Reaction ▫Loss of an electron ▫Reducing Agent  Provides Electrons (is oxidized) Reduction Reaction ▫Gain of an electron ▫Oxidizing Agent  Accepts Electrons (is reduced)

46. Redox Reactions  LEO the lion goes GER Lose Electrons – Oxidation Gain Electrons – Reduction H 2 + F 2 → 2HF Oxidation Reaction: H 2 → 2H + + 2e - Reduction Reaction: F 2 + 2e - → 2F -

47. Identify what is being oxidized and reduced in the following reactions. H 2 + O 2  H 2 O Fe + CuSO 4  FeSO 4 + Cu Fe + S 8  FeS Mg + HCl  MgCl 2 + H 2

48. Redox Reactions Combination Reactions 2H 2(g) + O 2(g)  2H 2 O (l) Decomposition Reactions 2H 2 O (l)  2H 2(g) + O 2(g) 2HgO (s) + heat  2Hg (l) + O 2(g) Combustion Reactions 2C 4 H 10(g) + 13O 2(g)  8CO 2(g) + 10H 2 O (l) + heat

49. Redox Reactions Displacement Reactions ▫Hydrogen Displacement Mg (s) + HCl (aq)  MgCl 2(aq) + H 2(g) ▫Metal Displacement Cu + AgCl  CuCl 2(aq) + Ag (s) ▫Halogen Displacement Cl 2(g) + 2KBr (aq)  2KCl (aq) + Br 2(l) ▫Disproportion Reaction 2H 2 O 2(aq)  2H 2 O (l) + O 2(g)

50. What are your questions?

51. Gravimetric Analysis An analytical technique based on the measurement of mass. A sample of unknown composition is reacted with another compound to form a precipitate. The ion you want to analyze for is the limiting reagent in the reaction. The precipitate is then filtered, dried and massed. This information is used to calculate the amount of ion(s) present in the initial compound. Very accurate, but only works well for reactions that produce 100% yield.

52. Gravimetric Analysis

53. An excess of Na 2 SO 4 is added to a solution containing soluble barium ion to produce BaSO 4. How many grams of barium ion are present in the solution if 565mg of BaSO 4 was produced?

54. An excess of HCl is added to a solution containing silver ion to produce AgCl. How many grams of silver ion are present in the solution if 1.6 of AgCl was produced?

55. 25mL of lead (II) nitrate solution of an unknown concentration was reacted with rubidium arsenate, Rb 3 AsO 4. After filtering and drying, 0.0814g of precipitate was formed. What was the concentration of lead (II) nitrate in the solution?

56. A 500mL sample of water was tested for silver content. An excess amount of sodium bromide was added to the sample to precipitate silver (I) bromide and produce sodium and nitrate ions. If 0.109g of silver bromide was produced, what is the concentration of silver per liter of water.

57. A 1.25L sample of river water was analyzed for Pb 2+ ions by adding excess Na 2 SO 4. If 231.6mg of PbSO 4 is produced, what is the concentration of Pb ion in the water?

58. Acid-Base Titrations Titration ▫Addition of a solution of a known concentration (standard solution) to a solution of unknown concentration until the reaction is complete (reaches its equivalence point) Volumetric Analysis Indicators ▫Utilized during titration to determine when the reaction is complete.

59. Acid-Base Titrations IndicatorpH Range Thymol blue 1.2 red 2.8 yellow 8.0 yellow 9.6 blue Methyl orange 3.1 red 4.4 yellow/orange Bromocresol green 3.8 yellow 5.4 blue Methyl red 4.4 red 6.2 yellow/orange Phenolphthalein 8.0 colorless 9.8 pink

61. How many mL of 0.45M NaOH are needed to neutralize 50mL of a 0.125M solution of HCl?

62. What is the concentration of a HNO 3 solution if 32mL reacts with 42.4mL if 0.150M Mg(OH) 2 in the following reaction? HNO 3(aq) + Mg(OH) 2(aq)  Mg(NO 3 ) 2(aq) + H 2 O (l)

63. What volume of 0.25M HNO 3 reacts with 42.4mL if 0.150M Na 2 CO 3 in the following reaction? 2HNO 3(aq) + Na 2 CO 3(aq)  2NaNO 3(aq) + H 2 O (l) + CO 2(g)

64. What is the concentration of a HBr solution when 50.0mL of the solution is titrated with 39.67mL of 0.175M KOH?

65. What volume of 0.30M acetic acid will react with 40.5mL if 0.275M sodium bicarbonate? What is the balanced chemical equation for this reaction?

66. What are your questions?