Chapter 4 Reactions in Aqueous Solution Chemistry: McMurry and Fay, 6th Edition Chapter 4: Reactions in Aqueous Solution 11/23/2018 6:54:02 AM Chapter 4 Reactions in Aqueous Solution © 2012 Pearson Education, Inc. Copyright © 2011 Pearson Prentice Hall, Inc.

Naming Chemical Compounds Chapter 2: Atoms, Molecules, and Ions 11/23/2018 Naming Chemical Compounds Binary Acids HCl hydrochloric acid HBr hydrobromic acid HF hydrofluoric acid Copyright © 2008 Pearson Prentice Hall, Inc. Copyright © 2008 Pearson Prentice Hall, Inc.

Naming Chemical Compounds Chapter 2: Atoms, Molecules, and Ions Naming Chemical Compounds 11/23/2018 Oxoacids do not begin with “hydro.” Hydrochloric acid: HCl Chloric acid: HClO3 “ous” “ite” “ic” “ate” Copyright © 2008 Pearson Prentice Hall, Inc. Copyright © 2008 Pearson Prentice Hall, Inc.

Examples Name the following acids HI HCN HNO3 H2PO4

Acids, Bases, and Neutralization Reactions Chapter 4: Reactions in Aqueous Solution 11/23/2018 Acids, Bases, and Neutralization Reactions Acid (Arrhenius): A substance that dissociates in water to produce hydrogen ions, H1+: H1+(aq) + A1-(aq) HA(aq) H1+(aq) + Cl1-(aq) HCl(aq) In water, acids produce hydronium ions, H3O1+: H3O1+(aq) + Cl1-(aq) HCl(aq) + H2O(aq) “HA” is a generic chemical formula for an acid. Hydrogen ions do not exist in water. They are attached to one or more water molecules (often in clusters). For convenience, we’ll write it as hydrogen ion instead of hydronium ion until a later chapter when a deeper look at acids and bases is undertaken. Copyright © 2008 Pearson Prentice Hall, Inc. Copyright © 2008 Pearson Prentice Hall, Inc.

Acids, Bases, and Neutralization Reactions Chapter 4: Reactions in Aqueous Solution 11/23/2018 Acids, Bases, and Neutralization Reactions Base (Arrhenius): A substance that dissociates in water to produce hydroxide ions, OH1-: M1+(aq) + OH1-(aq) MOH(aq) Na1+(aq) + OH1-(aq) NaOH(aq) Ammonia, commonly called “ammonium hydroxide” is a base: “M” is shorthand for a metal cation. It’s really not proper to call “aqueous ammonia” “ammonium hydroxide” even though it’s still commonly labeled as such (ordering chemicals, etc.). NH41+(aq) + OH1-(aq) NH3(aq) + H2O(aq) Copyright © 2008 Pearson Prentice Hall, Inc. Copyright © 2008 Pearson Prentice Hall, Inc.

Acids, Bases, and Neutralization Reactions Chapter 4: Reactions in Aqueous Solution 11/23/2018 Acids, Bases, and Neutralization Reactions Strong acids and strong bases are strong electrolytes. Weak acids and weak bases are weak electrolytes. Copyright © 2008 Pearson Prentice Hall, Inc. Copyright © 2008 Pearson Prentice Hall, Inc.

Acids, Bases, and Neutralization Reactions Chapter 4: Reactions in Aqueous Solution 11/23/2018 Acids, Bases, and Neutralization Reactions These acid-base neutralization reactions are double-replacement reactions just like the precipitation reactions: MA + HOH HA + MOH or Recall the original definition of an acid-base neutralization written earlier. While it looks goofy to write water as HOH, it can help students remember where the pieces came from: H (acid) and OH (base). It’s also easier to balance. MA + H2O HA + MOH Acid Base Salt Water Copyright © 2008 Pearson Prentice Hall, Inc. Copyright © 2008 Pearson Prentice Hall, Inc.

Acids, Bases, and Neutralization Reactions Chapter 4: Reactions in Aqueous Solution 11/23/2018 Acids, Bases, and Neutralization Reactions Write the molecular, ionic, and net ionic equations for the reaction of aqueous HBr and aqueous Ba(OH)2. 1. Write the chemical formulas of the products (use proper ionic rules for the salt). HBr(aq) + Ba(OH)2(aq) H2O + BaBr2 Acid Base Water Salt The order the products are written in is irrelevant. The products will be water and a salt. The salt is written using the rules for naming ionic compounds as previously used. Copyright © 2008 Pearson Prentice Hall, Inc. Copyright © 2008 Pearson Prentice Hall, Inc.

Acids, Bases, and Neutralization Reactions Chapter 4: Reactions in Aqueous Solution 11/23/2018 Acids, Bases, and Neutralization Reactions Write the molecular, ionic, and net ionic equations for the reaction of aqueous NaOH and aqueous HF. 1. Write the chemical formulas of the products (use proper ionic rules for the salt). HF(aq) + NaOH(aq) H2O + NaF Acid Base Water Salt Copyright © 2008 Pearson Prentice Hall, Inc. Copyright © 2008 Pearson Prentice Hall, Inc.

Examples Predict the product and write a molecular equation, ionic equation and net ionic equation for the following reactions K2CO3(aq) + NiCl2(aq)  H2NO3(aq) + LiOH(aq)  HCN(aq) + Mg(OH)2

Oxidation-Reduction (Redox) Reactions Chapter 4: Reactions in Aqueous Solution 11/23/2018 Oxidation-Reduction (Redox) Reactions Rusting of iron: an oxidation of Fe 2Fe2O3(s) 4Fe(s) + 3O2(g) Manufacture of iron: a reduction of Fe 4Fe(s) + 3CO2(g) 2Fe2O3(s) + 3C(s) Copyright © 2008 Pearson Prentice Hall, Inc. Copyright © 2008 Pearson Prentice Hall, Inc.

Oxidation-Reduction (Redox) Reactions Chapter 4: Reactions in Aqueous Solution 11/23/2018 Oxidation-Reduction (Redox) Reactions Oxidation Number (State): A value which indicates whether an atom is neutral, electron-rich, or electron-poor. Rules for Assigning Oxidation Numbers An atom in its elemental state has an oxidation number of 0. Na H2 Br2 S Ne Oxidation number 0 Copyright © 2008 Pearson Prentice Hall, Inc. Copyright © 2008 Pearson Prentice Hall, Inc.

Oxidation-Reduction (Redox) Reactions Chapter 4: Reactions in Aqueous Solution 11/23/2018 Oxidation-Reduction (Redox) Reactions A monatomic ion has an oxidation number identical to its charge. Na1+ +1 Ca2+ +2 Al3+ +3 Cl1- -1 O2- -2 This is why charges are supposed to be written as “1-”. The corresponding oxidation number is written “-1”. Copyright © 2008 Pearson Prentice Hall, Inc. Copyright © 2008 Pearson Prentice Hall, Inc.

Oxidation-Reduction (Redox) Reactions Chapter 4: Reactions in Aqueous Solution 11/23/2018 Oxidation-Reduction (Redox) Reactions An atom in a polyatomic ion or in a molecular compound usually has the same oxidation number it would have if it were a monatomic ion. Hydrogen can be either +1 or -1. H O 1- H Ca +1 -2 -1 +2 -1 Oxygen usually has an oxidation number of -2. H O H O O H H bonded to a nonmetal has an oxidation number of +1. H bonded to a metal has an oxidation number of -1. In peroxides, O22-, oxygen has an oxidation number of -1. +1 -2 +1 +1 -1 -1 +1 Copyright © 2008 Pearson Prentice Hall, Inc. Copyright © 2008 Pearson Prentice Hall, Inc.

Oxidation-Reduction (Redox) Reactions Chapter 4: Reactions in Aqueous Solution 11/23/2018 Oxidation-Reduction (Redox) Reactions Halogens usually have an oxidation number of -1. 3. H Cl Cl O +1 -1 +1 -2 +1 A major exception is when the halogen is bonded to oxygen. Copyright © 2008 Pearson Prentice Hall, Inc. Copyright © 2008 Pearson Prentice Hall, Inc.

Oxidation-Reduction (Redox) Reactions Chapter 4: Reactions in Aqueous Solution 11/23/2018 Oxidation-Reduction (Redox) Reactions The sum of the oxidation numbers is 0 for a neutral compound and is equal to the net charge for a polyatomic ion. 2(+1) + x + 3(-2) = 0 (net charge) H2SO3 x = +4 +1 x -2 Cr2O72- 2(x) + 7(-2) = -2 (net charge) x = +6 x -2 Copyright © 2008 Pearson Prentice Hall, Inc. Copyright © 2008 Pearson Prentice Hall, Inc.

Example Determine the oxidation number for each atom in the following compounds/molecules SrBr2 CCl4 SO42-

Identifying Redox Reactions Chapter 4: Reactions in Aqueous Solution 11/23/2018 Identifying Redox Reactions Oxidizing Agent Causes oxidation Gains one or more electrons Undergoes reduction Oxidation number of atom decreases Reducing Agent Causes reduction Loses one or more electrons Undergoes oxidation Oxidation number of atom increases An “agent” causes something to happen. Copyright © 2008 Pearson Prentice Hall, Inc. Copyright © 2008 Pearson Prentice Hall, Inc.

Identifying Redox Reactions Chapter 4: Reactions in Aqueous Solution 11/23/2018 Identifying Redox Reactions Oxidizing Agent 2Fe2 3O2(g) + 4Fe(s) O3 (s) +3 oxidation reduction -2 Reducing Agent Copyright © 2008 Pearson Prentice Hall, Inc. Copyright © 2008 Pearson Prentice Hall, Inc.

Example Identify each of the following as 1) oxidation or 2) reduction. __A. Sn(s) Sn4+(aq) + 4e− __B. Fe3+(aq) + 1e− Fe2+(aq) __C. Cl2(g) + 2e− 2Cl-(aq)

Writing Oxidation and Reduction Reactions Write the separate half oxidation and reduction reactions for the following equation. 2Cs(s) + F2(g) 2CsF(s) 3 Na(l) + AlCl3(l) 3  NaCl(l) + Al(l)

The Activity Series of the Elements Chapter 4: Reactions in Aqueous Solution 11/23/2018 The Activity Series of the Elements Cu2+(aq) + 2Ag(s) Cu(s) + 2Ag1+(g) Which one of these reactions will occur? 2Ag1+(aq) + Cu(s) 2Ag(s) + Cu2+(g) These are net ionic equations. The spectator ions (nitrate, for one example) are not involved in the main reaction. Copyright © 2008 Pearson Prentice Hall, Inc. Copyright © 2008 Pearson Prentice Hall, Inc.

The Activity Series of the Elements Chemistry: McMurry and Fay, 6th Edition Chapter 4: Reactions in Aqueous Solution 11/23/2018 6:54:02 AM The Activity Series of the Elements Fe2+(aq) + Cu(s) Fe(s) + Cu2+(aq) This is a net ionic equation. The spectator ions (nitrate, for one example) are not involved in the main reaction. © 2012 Pearson Education, Inc. Copyright © 2011 Pearson Prentice Hall, Inc.

The Activity Series of the Elements Chemistry: McMurry and Fay, 6th Edition Chapter 4: Reactions in Aqueous Solution 11/23/2018 6:54:02 AM The Activity Series of the Elements Elements that are higher up in the table are more likely to be oxidized. Thus, any element higher in the activity series will reduce the ion of any element lower in the activity series. © 2012 Pearson Education, Inc. Copyright © 2011 Pearson Prentice Hall, Inc.

The Activity Series of the Elements Chapter 4: Reactions in Aqueous Solution 11/23/2018 The Activity Series of the Elements Cu2+(aq) + 2Ag(s) Cu(s) + 2Ag1+(g) Which one of these reactions will occur? 2Ag1+(aq) + Cu(s) 2Ag(s) + Cu2+(g) This is a nice one to do as a demonstration. Place a coil of copper wire in a solution of silver nitrate at the beginning of lecture or lab and show it to the students. Show it again at the end of the period. Copyright © 2008 Pearson Prentice Hall, Inc. Copyright © 2008 Pearson Prentice Hall, Inc.

Example Predict whether the following redox reactions will occurred or not. If so, predict the products Zn(s) + FeCl2(aq)  Ni(s) + Mg(NO3)2(aq) 

Chapter 4: Reactions in Aqueous Solution Redox Titrations 11/23/2018 Titration: A procedure for determining the concentration of a solution by allowing a carefully measured volume to react with a solution of another substance (the standard solution) whose concentration is known. 5H2C2O4(aq) + 2MnO41-(aq) + 6H1+(aq) 10CO2(g) + 2Mn2+(aq) + 8H2O(l) If the unknown concentration is the potassium permanganate solution, MnO41-, it can be slowly added to a known amount of oxalic acid, H2C2O4, until a faint purple color persists. The net ionic equation is shown. Potassium permanganate is dark purple. As it’s added to a solution of oxalic acid, the permanganate reacts to form Mn2+ and remains colorless (dilute solutions of Mn2+ are colored but it can be difficult to see). When a slight excess of permanganate is added, the solution turns faint purple. Copyright © 2008 Pearson Prentice Hall, Inc. Copyright © 2008 Pearson Prentice Hall, Inc.

Chapter 4: Reactions in Aqueous Solution 11/23/2018 Redox Titrations A solution is prepared with 0.2585 g of oxalic acid, H2C2O4. 22.35 mL of an unknown solution of potassium permanganate are needed to titrate the solution. What is the concentration of the potassium permanganate solution? 5H2C2O4(aq) + 2MnO41-(aq) + 6H1+(aq) 10CO2(g) + 2Mn2+(aq) + 8H2O(l) Copyright © 2008 Pearson Prentice Hall, Inc. Copyright © 2008 Pearson Prentice Hall, Inc.

Calculation Set up Mass of H2C2O4 Moles of H2C2O4 Moles of KMnO4 Molarity of KMnO4 Mole Ratio Molar Mass of H2C2O4 Molarity of KMnO4

Example A 0.0484M standard solution of potassium permanganate was titrated against 25.00mL of an iron (II) sulfate solution. The equivalence point, as indicated by a faint pink color, was reached when 15.50mL of potassium permanganate solution had been added. Calculate the concentration of the iron (II) sulfate solution