1. © Copyright 1995-2007 R.J. Rusay Aqueous Reactions Dr. Ron Rusay Fall 2007

2. © Copyright 1995-2007 R.J. Rusay Aqueous Reactions  There are several general types: 1) Precipitation: An insoluble salt forms from the addition of solutions. (Refer to Solubility Rules) 2) Acid-Base Reactions (Neutralization) generally produces a salt plus water 3) Oxidation-Reduction (Redox) there is a change in oxidation numbers between reactants and products

3. Solution Test Apparatus for Electrolytes

4. © Copyright 1995-2007 R.J. Rusay Conductivity

5. Electrolytes  Aqueous solutions can be categorized into 3 types: non-electrolytes, strong electrolytes or weak electrolytes based on their ability to conduct electricity.  A solution must have ions to conduct.  Pure Water does not conduct.  Aqueous solutions can be tested for conductivity which will determine the degree of ionization of the solutes.  It is possible to have full or partial ionization.

6. © Copyright 1995-2007 R.J. Rusay Electrolytes  Almost all ionic compounds and a few molecular compounds are strong electrolytes.  Several molecular compounds are weak conductors, most are non-conductors.  Conductivity is directly related to the amount of ionization, i.e. ions in solution. Table salt, sodium chloride, is completely ionized: NaCl (s) + H 2 O (l) ---> NaCl (aq) ---> 0.10MNa + (aq) + Cl - (aq) 0.00M 0.10M 0.10M

7. © Copyright 1995-2007 R.J. Rusay Electrolytes � Concentrations: � 2 2 � CaCl 2 (s) + H 2 O (l) ---> CaCl 2(aq) ---> 0.10MCa 2+ (aq) + 2 Cl - (aq) 0.00M 0.10M 0.20M

8. © Copyright 1995-2007 R.J. Rusay Electrolytes  Sugars like sucrose are non-ionic, molecular compounds that dissolve but produce no ions. C 12 H 22 O 11 (S) + H 2 O (l) ----> C 12 H 22 O 11 (aq)  Some molecular compounds like acetic acid ionize partially (dissociate) in water HC 2 H 3 O 2 (l) + H 2 O (l) H 3 O + (aq) + 0.1000M C 2 H 3 O 2 - (aq) 0.9987M0.0013M

9. © Copyright 1995-2007 R.J. Rusay Aqueous Acids � Any compound that provides a proton can be considered an acid. Strong acids are sulfuric acid, nitric acid, perchloric acid, HI, HBr and HCl.

10. © Copyright 1995-2007 R.J. Rusay Electrolytes � How would the conductivity of acetic acid compare to hydrochloric acid?

11. Figure 4.6 HCl is Completely Ionized Figure 4.8 Acetic Acid (HC 2 H 3 O 2 )

12. © Copyright 1995-2007 R.J. Rusay Aqueous Bases  Any compound that accepts a proton is a base.  The common bases are group IA & IIA metal hydroxide compounds. They are strong bases, dissociating completely in water.  An example of a weak base is ammonia. NH 3 (g) + H 2 O (l) NH 3 (aq) NH 4 + (aq) + OH - (aq)

13. Figure 4.7 An Aqueous Solution of Sodium Hydroxide Figure 4.9 The Reaction of NH 3 in Water

15. QUESTION

16. ANSWER. 2)HBr Section 4.2 The Nature of Aqueous Solutions: Strong and Weak Electrolytes (p. 129) Knowing the list of strong acids will allow one to determine which acids are strong and which are weak.

17. © Copyright 1995-2007 R.J. Rusay Aqueous Reactions: Neutralization

18. © Copyright 1995-2007 R.J. Rusay Aqueous Reactions: Neutralization Net Ionic Equations HCl (aq) + NaOH (aq) ---> NaCl (aq) + H 2 O (l) ___________________________________________________ � � HCl (aq) ---> H + (aq) + Cl - (aq) � � NaOH (aq) ---> Na + (aq) + OH - (aq) � � NaCl (aq) ---> Na + (aq) + Cl - (aq) ________________________________________________ Na + (aq) + OH - (aq) + H + (aq) + Cl - (aq) ---> Na + (aq) + Cl - (aq) + H 2 O (l) _______________________________________________________ H + (aq) + OH - (aq) ---> H 2 O (l)

19. © Copyright 1995-2007 R.J. Rusay Aqueous Reactions: Acid-Base

20. QUESTION If an antacid contains Al(OH) 3 it will form AlCl 3 upon neutralization of stomach acid. How many moles of Cl – ions are in 100.0 mL of 0.010 M AlCl 3 ? 1.0.001 0 M 2.0.010 M 3.0.003 0 M 4.0.030 M

21. ANSWER Choice 3 accounts for both the stoichiometry of dissociation and the concentration. After multiplying the volume, in liters, by the molarity of the solution, the stoichiometry must be considered. AlCl 3 dissociates into 3 moles of Cl –. Section 4.3: The Composition of Solutions

22. QUESTION If an antacid contains Al(OH) 3 it will form AlCl 3 upon neutralization of stomach acid. What is the molarity of Cl – ions in 100.0 mL of 0.010 M AlCl 3 ? 1.0.001 0 M 2.0.010 M 3.0.003 0 M 4.0.030 M

23. ANSWER Choice 4 accounts for both the stoichiometry of dissociation and the concentration. Since the volume remains constant the molarity of the solution is adjusted only by the stoichiometry: 1 mole of AlCl 3 dissociates into 3 moles of Cl –. Section 4.3: The Composition of Solutions

24. QUESTION

25. ANSWER 5) Na 2 SO 4 + 2H 2 O Section 4.8 Acid-Base Reactions (p. 149) The salt is made from the anion of the acid and the cation of the base.

26. Pb(NO 3 ) 2 (aq) + NaI (aq)  NaNO 3 (aq) + PbI 2 (s) How do you know the state of the products: (s) vs. (aq)? What type of reaction is it? Double Displacement & Precipitation Write a balanced equation for the reaction. 2 2

28. QUESTION Given the insoluble compound Al 2 (CO 3 ) 3 predict the ions and coefficients that would be necessary to complete the following net ionic equation: __ _____ + ____ _____  Al 2 (CO 3 ) 3 1.2 AlCl 3 + 3 Na 2 CO 3 also include 6 NaCl on right 2.3 Al 3+ + 2 CO 3 2– 3.2 Al 3+ + 3 CO 3 2– 4.2 Al 3+ 6 Cl – + 3 CO 3 2– + 6 Na +

29. ANSWER Choice 3 correctly depicts the completed net ionic equation. Only those soluble reacting ions that form the compound need to be shown. The other ions could be considered spectator ions. Section 4.6: Describing Reactions in Solution

30. © Copyright 1995-2007 R.J. Rusay Aqueous Reactions: Precipitation Net Ionic Equations  50mL of a 0.1M solution of sodium sulfate is mixed with 50mL of a 0.2M solution of silver nitrate. What is the result?  Molecular Equation: ?Na 2 SO 4(aq) + ?AgNO 3(aq) ---> ?Na 2 SO 4(aq) + ?AgNO 3(aq) ---> ?Ag 2 SO 4(s) + ?NaNO 3(aq) 1 2 12

31. © Copyright 1995-2007 R.J. Rusay Aqueous Reactions: Precipitation Net Ionic Equations Na 2 SO 4(aq) + 2 AgNO 3(aq) -->Ag 2 SO 4(s) + 0.1M0.2M 2 NaNO 3(aq) Ionic Reaction (Reactants): Na 2 SO 4(aq)  2 Na + (aq) + SO 4 2- (aq) 2 AgNO 3(aq)  2 Ag + (aq) + 2 NO 3 1- (aq) 2 AgNO 3(aq)  2 Ag + (aq) + 2 NO 3 1- (aq) 2 Na + (aq) + SO 4 2- (aq) + 2 Ag + (aq) + 2 NO 3 1- (aq) 0.2M0.1M0.2M 0.2M 0.2M0.1M0.2M 0.2M

32. © Copyright 1995-2007 R.J. Rusay Aqueous Reactions: Precipitation Net Ionic Equations Na 2 SO 4(aq) + 2 AgNO 3(aq) -->Ag 2 SO 4(s) + 0.1M0.2M 2 NaNO 3(aq) Ionic Reaction (Products): 2 NaNO 3(aq)  2 Na + (aq) + 2 NO 3 1- (aq) Ag 2 SO 4(s)  Does not dissolve (ionize) Ag 2 SO 4(s)  Does not dissolve (ionize) 2Na + (aq) + 2NO 3 1- (aq) + Ag 2 SO 4(s) 0.2M 0.2M solid 0.2M 0.2M solid

33. © Copyright 1995-2007 R.J. Rusay Aqueous Reactions: Precipitation Net Ionic Equations Na 2 SO 4(aq) + 2 AgNO 3(aq) -->Ag 2 SO 4(s) + 2 NaNO 3(aq) Overall Ionic Reaction: 2Na + (aq) + SO 4 2- (aq) +2Ag + (aq) + 2NO 3 1- (aq)  2Na + (aq) + Ag 2 SO 4(s) + 2NO 3 1- (aq) Net Ionic Equation: (Subtract Spectator Ions) 2Ag + (aq) + SO 4 2- (aq)  Ag 2 SO 4(s) = M Na2SO4 xV Na2SO4 / 1:1 stoichiometry = 0.10M x 0.050 L/ 1 = 0.0050 mol How many moles?

34. QUESTION

35. ANSWER – 3)3OH(aq) Section 4.6 Describing Reactions in Solution (p. 145) The net ionic equation is found by canceling the spectator ions from the total ionic equation.

36. Pb(NO 3 ) 2 (aq) + NaI (aq)  NaNO 3 (aq) + PbI 2 (s) Write a balanced Net Ionic equation for the reaction. 2 2 Pb 2+ ( aq) + 2 I 1- (aq)  PbI 2 (s) What are the spectator ions in the reaction? 2 Na 1+ ( aq) ; 2 NO 3 1- (aq)

37. QUESTION

38. ANSWER 5)All of these are soluble in water. Section 4.5 Precipitation Reactions (p. 140) According to the solubility rules for ionic compounds, compounds containing Group IA ions or nitrate ions will always be soluble. Compounds containing halides are generally soluble, aside from silver, leadand mercury(I) halides.

39. QUESTION If you began a reaction with the following ions in solution (all would be written with an aq subscript) how would you represent the proper final net ionic equation? (Consult a solubility Table.) 6Na + + 2PO 4 3– + 3Fe 2+ + 6NO 3 –  1.3Na + + PO 4 3– + Fe 2+ + 2NO 3 –  No Reaction 2.6Na + + 2PO 4 3– + 3Fe 2+ + 6NO 3 –  Fe 3 (PO 4 ) 2 (s)+ 6NaNO 3 3.3Na + + PO 4 3– + Fe 2+ + 2NO 3 –  Fe 3 (PO 4 ) 2 (s)+ 6 Na + + 6 NO 3 – 4.2PO 4 3– + 3Fe 2+  Fe 3 (PO 4 ) 2 (s)

40. ANSWER Choice 4 correctly depicts the reacting ions and the resulting solid product. Use the chart to determine if an insoluble solid will be produced by the combination of ions given. If so, write that and balance the atoms. If soluble ions from strong electrolytes are present, they may cancel out from the left and right side of the equation. Section 4.5: Precipitation Reactions

41. © Copyright 1995-2007 R.J. Rusay Aqueous Reactions: Oxidation - Reduction � In the following reaction, identify what is being oxidized and what is being reduced. What is the total number of electrons involved in the process?

42. © Copyright 1995-2007 R.J. Rusay

43. QUESTION In a redox reaction, oxidation and reduction must both occur. Which statement provides an accurate premise of redox chemistry? 1.The substance that is oxidized must be the oxidizing agent. 2.The substance that is oxidized must gain electrons. 3.The substance that is oxidized must have a higher oxidation number afterwards. 4.The substance that is oxidized must combine with oxygen.

44. ANSWER Choice 3 displays the proper connection between oxidation and oxidation number. During oxidation negatively charged electrons leave the atom thereby increasing the oxidation number charge. Section 4.9: Oxidation–Reduction Reactions

45. © Copyright 1995-2007 R.J. Rusay