Chemical Change Chapter 9 Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Section 9.1 Electrolytes and Solution Conductivity Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Goal 1 Distinguish among strong electrolytes, weak electrolytes, and nonelectrolytes. Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Electrical Conductivity Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

A substance that, when dissolved in water, Strong Electrolyte: A substance that, when dissolved in water, conducts electricity strongly Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

A substance that, when dissolved in water, Weak Electrolyte: A substance that, when dissolved in water, conducts electricity, but does so poorly Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

A substance that, when dissolved in water, Nonelectrolyte: A substance that, when dissolved in water, does not conduct electricity Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Conducting solutions contain ions The extent of conductivity is related to the concentration of ions in the solution Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Section 9.2 Solutions of Ionic Compounds Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Goal 2 Given the formula of an ionic compound (or its name), write the formula of the ions present when it is dissolved in water. Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

The ions are identified by separating the compound into its ions When an ionic compound dissolves in water, its solution consists of water molecules and ions The ions are identified by separating the compound into its ions NaCl(s) Na+(aq) + Cl–(aq) Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Na+(aq) + Cl–(aq) NaCl(s) Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

K2SO4(s) 2 K+(aq) + SO42–(aq) Polyatomic ions are treated in the same way in writing the formulas of ions in solution K2SO4(s) 2 K+(aq) + SO42–(aq) Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Section 9.3 Strong and Weak Acids Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Goal 3 Explain why the solution of an acid may be a good conductor or a poor conductor of electricity. Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Goal 4 Given the formula of a soluble acid (or its name), write the major and minor species present when it is dissolved in water. Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Acid: Hydrogen-bearing molecular compound made up of nonmetal elements that reacts with water to form a hydrated hydrogen ion and an anion HX H2O + H3O+ + X– > Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Acid solutions can be strong or weak electrolytes, depending on the extent to which the acid molecule ionizes in solution Strong acid: Ionizes almost completely HSt(aq) H+(aq) + St–(aq) Major species: ions Minor species: molecules Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

HWe(aq) H+(aq) + We–(aq) Weak acid: Ionizes very slightly HWe(aq) H+(aq) + We–(aq) Major species: molecules Minor species: ions Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Strong and weak acids at the macroscopic and particulate levels Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Seven Common Strong Acids HNO3 H2SO4 Two Well- Known Acids HBr HCl HI Three Group 7A/17 Acids HClO3 HClO4 Two Chlorine Oxyacids Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Identifying the Major Species in a Solution Ions are the major species in the solutions of two kinds of substances: All soluble ionic compounds The seven strong acids Neutral molecules are the major species in solutions of everything else, primarily: Weak acids Weak bases Water Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Section 9.4 Net Ionic Equations: What They Are and How to Write Them Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Consider the reaction of solutions of silver nitrate and sodium chloride What is the particulate-level composition of each solution before the reaction occurs? Silver nitrate solution: Silver ions, Ag+(aq) Nitrate ions, NO3–(aq) Water molecules Sodium chloride solution: Sodium ions, Na+(aq) Chloride ions, Cl–(aq) Water molecules Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

How are these represented in a conventional equation? AgNO3(aq) + NaCl(aq) The problem with this conventional representation is that it disguises the true composition of the solutions Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

To avoid this misrepresentation, we can write the formulas of the reactants as they actually occur in solution Ag+(aq) + NO3–(aq) + Na+(aq) + Cl–(aq) Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

We can perform a similar analysis with the products of the reaction Silver chloride precipitate: Solid silver chloride, AgCl(s) Sodium nitrate solution: Sodium ions, Na+(aq) Nitrate ions, NO3–(aq) Water molecules Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Conventional representation of products: AgCl(s) + NaNO3(aq) Products as they actually occur: AgCl(s) + Na+(aq) + NO3–(aq) Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Combining reactants and products: AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq) This is the conventional equation It is good for stoichiometry problems but lacks in revealing what really happens in solution Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Writing actual reactants and products: AgCl(s) + Na+(aq) + NO3–(aq) Ag+(aq) + NO3–(aq) + Na+(aq) + Cl–(aq) This is the total ionic equation It represents each species as it actually occurs in solution Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Note that some species appear as both reactant and product in the total ionic equation: Ag+(aq) + NO3–(aq) + Na+(aq) + Cl–(aq) AgCl(s) + Na+(aq) + NO3–(aq) NO3–(aq) is both reactant and product; Na+(aq) is both reactant and product Neither ion undergoes a chemical change Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

If we eliminate these non-reacting spectator ions, Ag+(aq) + NO3–(aq) + Na+(aq) + Cl–(aq) AgCl(s) + Na+(aq) + NO3–(aq) What remains is the net ionic equation: Ag+(aq) + Cl–(aq) AgCl(s) Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

A net ionic equation describes what happens in a chemical change Aqueous silver ion reacts with aqueous chloride ion to yield solid silver chloride A net ionic equation ignores non-reacting species: Sodium ion Nitrate ion Water molecules Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

How to write a net ionic equation Procedure: How to write a net ionic equation 1. Write the conventional equation. Include state symbols. 2. Write the total ionic equation. Solids, liquids, and gases do not ionize. Aqueous compounds may ionize: A. Ionic compounds and strong acids ionize B. Weak acids do not ionize 3. Write the net ionic equation. Eliminate the spectators. Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Section 9.7 Double-Replacement Precipitation Reactions Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Goal 7 Predict whether a precipitate will form when known solutions are combined; if a precipitate forms, write the net ionic equation. (Reference to a solubility table or solubility rules may or may not be allowed.) Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Goal 8 Given the product of a precipitation reaction, write the net ionic equation. Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Precipitation Reactions Double-Replacement Precipitation Reactions Reactants: Reaction type: Equation type: Products: Solutions of two ionic compounds or a solution of an ionic compound and an acid solution Double-replacement precipitation AX + BY AY + BX Precipitate of ionic compound and second ionic compound or acid Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Example: Calcium nitrate and potassium sulfate solutions are combined. Write the net ionic equation. Ca(NO3)2(aq) + K2SO4(aq) CaSO4( ) + KNO3( ) 2 Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Conventional equation: Ca(NO3)2(aq) + K2SO4(aq) CaSO4(s) + KNO3(aq) 2 Total ionic equation: Ca2+(aq) + 2 NO3–(aq) + 2 K+(aq) + SO42–(aq) CaSO4(s) + 2 K+(aq) + 2 NO3–(aq) Net ionic equation: Ca2+(aq) + SO42–(aq) CaSO4(s) Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Section 9.8 Double-Replacement Molecule-Formation Reactions Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Goal 9 Given reactants that yield a molecular product, write the net ionic equation. Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Ion Combinations That Form Molecules The reaction of an acid often leads to an ion combination that yields a molecular product, typically water or a weak acid Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Neutralization Reactions Double-Replacement Neutralization Reactions Reactants: Reaction type: Equation type: Products: Acid (HX) and a hydroxide base (MOH) Double-replacement neutralization HX + MOH H2O + HX Water and a salt (MX) (an ionic compound) Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Write the net ionic equation for Example: Write the net ionic equation for the reaction of solutions of hydrobromic acid and sodium benzoate (benzoate ion, C7H5O2–). Conventional equation: HBr(aq) + NaC7H5O2(aq) HC7H5O2(aq) + NaBr(aq) HC7H5O2 is a weak acid NaBr: Group 1A salts are soluble Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Conventional equation: HBr(aq) + NaC7H5O2(aq) HC7H5O2(aq) + NaBr(aq) Total ionic equation: H+(aq) + Br–(aq) + Na+(aq) + C7H5O2–(aq) HC7H5O2(aq) + Na+(aq) + Br–(aq) Net ionic equation: H+(aq) + C7H5O2–(aq) HC7H5O2(aq) Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Section 9.9 Double-Replacement Reactions That Form Unstable Products Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Goal 10 Given reactants that form H2CO3, H2SO3, or “NH4OH” by ion combination, write the net ionic equation for the reaction. Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Three common unstable products: H2CO3(aq) H2O(l) + CO2(g) H2SO3(aq) H2O(l) + SO2(aq) “NH4OH” NH3(aq) + H2O(l) Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Write the net ionic equation for the Example: Write the net ionic equation for the reaction that occurs when hydrochloric acid and sodium sulfite solutions are combined. Conventional equation: 2 HCl(aq) + Na2SO3(aq) H2SO3( ) + NaCl( ) aq H2O(l) + SO2(aq) Group 1A salts are soluble Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

Conventional equation: 2 HCl(aq) + Na2SO3(aq) H2O(l) + SO2(aq) + 2 NaCl(aq) Total ionic equation: 2 H+(aq) + 2 Cl–(aq) + 2 Na+(aq) + SO32–(aq) H2O(l) + SO2(aq) + 2 Na+(aq) + 2 Cl–(aq) Net ionic equation: 2 H+(aq) + SO32–(aq) H2O(l) + SO2(aq) Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.