Quiz 2

Chapter Goals 1

  • Properties of Aqueous Solutions of Acids and Bases

  • The Arrhenius Theory

  • The Hydronium Ion (Hydrated Hydrogen Ion)

  • The BrØnsted-Lowry Theory

  • The Autoionization of Water

  • Amphoterism

  • Strengths of Acids

Chapter Goals 2

  • Acid-Base Reactions in Aqueous Solutions

  • Acidic Salts and Basic Salts

  • The Lewis Theory

  • The Preparation of Acids

Properties of Aqueous Solutions of Acids and Bases 1

Aqueous Acidic Solutions

  • Taste: Sour taste.

  • Indicator Effect:

    • Acids turn blue litmus to red.

    • Acids turn bromothymol blue from blue to yellow.

  • Reaction with Metals:

    • React with metals to generate hydrogen gas, represented as H2(g).

Properties of Aqueous Solutions of Acids and Bases 2

Aqueous Acidic Solutions continued

  • Reactions:

    • React with metal oxides and hydroxides to form salts and water.

    • React with salts of weaker acids, resulting in the formation of the weaker acid and the salt of the stronger acid.

  • Electrical Conductivity:

    • Acidic aqueous solutions are capable of conducting electricity.

Properties of Aqueous Solutions of Acids and Bases 3

Aqueous Basic Solutions

  • Taste: Bitter taste.

  • Texture: Slippery feeling.

  • Indicator Effect:

    • Bases turn red litmus to blue.

    • Bases turn bromothymol blue from yellow to blue.

  • Reaction with Acids:

    • React with acids to form salts and water.

  • Electrical Conductivity:

    • Aqueous basic solutions also conduct electricity.

The Arrhenius Theory

Introduction

  • Originator: Svante Augustus Arrhenius presented this theory in 1884.

Definition of Acids

  • Definition: Acids are substances that contain hydrogen and produce H+ ions in aqueous solutions.

  • Examples: (not provided)

The Arrhenius Theory 2

Definition of Bases

  • Definition: Bases are substances that contain the hydroxyl (OH) group and produce hydroxide ions (OH-) in aqueous solutions.

  • Examples: (not provided)

The Arrhenius Theory 3

Neutralization Reactions

  • Definition: Neutralization reactions involve the combination of H+ (or H3O+) with OH- to form water (H2O).

  • Strong Acids: Strong acids are those that ionize 100% in water.

    • List of Strong Acids:

    • HCl

    • HBr

    • HI

    • H2SO4

    • HNO3

    • HClO4

    • HClO3

  • Strong Bases: Strong bases also ionize 100% in water.

    • List of Strong Bases:

    • LiOH

    • NaOH

    • KOH

    • RbOH

    • CsOH

    • Ca(OH)2

    • Sr(OH)2

    • Ba(OH)2

The BrØnsted-Lowry Theory 1

Introduction

  • Originators: J.N. BrØnsted and T.M. Lowry developed this theory in 1923.

Definitions

  • Acid: Defined as a proton donor (H+).

  • Base: Defined as a proton acceptor.

The BrØnsted-Lowry Theory 2

Acid-Base Reactions

  • Nature of Reactions: Acid-base reactions involve the transfer of a proton from an acid to a base.

  • Coordinate Covalent Bonds: These bonds are often formed in acid-base reactions.

The BrØnsted-Lowry Theory 3

Conjugate Acid-Base Pairs

  • Definition: Two species differing by a proton are called acid-base conjugate pairs.

    • Example Reaction:

    • Reaction: HNO3 + H2O → H3O+ + NO3–

    • Identify Reactants: Acid and base need to be identified.

    • Conjugate Base Identification: The species differing from the acid by a proton is the conjugate base.

The BrØnsted-Lowry Theory 4

Writing Conjugate Acid-Base Pairs

  • Standard format:

    • Example: HF + H₂O ⇒ H₃O⁺ + F⁻

    • Components: Acid (HF), base (H₂O), conjugate acid (H₃O⁺), conjugate base (F⁻).

The BrØnsted-Lowry Theory 5

Differences from Arrhenius Theory

  • Reaction Medium: Reactions do not have to occur in an aqueous solution.

  • Base Definition: Bases need not be hydroxides according to BrØnsted-Lowry.

The BrØnsted-Lowry Theory 6

Strength Comparison

  • Weak vs Strong Bases:

    • Example: NH3 is a weak base, suggesting NH4+ must be a strong acid as it can donate H+ to reform NH3.

    • Comparison with NaOH: NaOH fully ionizes 100% in water, making it a strong base.

The Autoionization of Water

Concept

  • Nature of Autoionization: Water autoionizes to a very limited extent.

    • Concentration Equation: [H3O+] = [OH–] ≈ 1.0 x 10^-7 M

  • Connection: This autoionization principle underpins the pH scale discussed in Chapter 18.

Amphoterism

Dual Behavior

  • Definition: Species that can function as both acids and bases are termed amphoteric.

  • Proton Transfer Reactions: Those that can act as either an acid or base in proton transfer reactions are termed amphiprotic.

Strengths of Acids 1

Factors Influencing Strength

  • Binary Acids: Acid strength increases as the H-X bond strength decreases.

  • Periodic Trend of Bond Strength:

    • HF > HCl > HBr > HI (Strongest bond to weakest bond)

    • Acid Strength Trend: HF < HCl < HBr < HI (Weakest acid to strongest acid)

Strengths of Acids 2

Ranking Acids and Bases

  • BrØnsted-Lowry Theory Application: Enables construction of relative rankings for acid and base strengths and their conjugate partners.

Strengths of Acids 3

General Strength Assessment

  • All Acids/Bases Ranked: This analysis is possible for virtually all acids and bases and their conjugate pairs.

  • Example Table:

    • Acid-Base Pairs:

    • HCIO is 100% ionized in dilute aqueous solution.

    • HI with negligible base strength in water.

    • HBr, HNO3, HF with respective conjugate bases like Br⁻, NO3⁻, F⁻.

    • NH4+ reacts completely with water forming OH– and cannot exist unassociated in aqueous solution.

Strengths of Acids 4

Ternary Acids Strength

  • Ternary Acid Strength Factors:

    • Increases with:

    • An increasing number of O atoms on the central atom.

    • An increasing oxidation state of the central atom.

  • Principle Explanation: Additional O atoms increase the oxidation state of the central atom by 2 for each atom added.

Acid-Base Reactions in Aqueous Solutions

Types of Reactions

  • Reactions Possible: Four combinations exist:

    • Strong acids with strong bases.

    • Weak acids with strong bases.

    • Strong acids with weak bases.

    • Weak acids with weak bases.

  • Example Review: Each type of acid-base reaction will be explored.

The Lewis Theory

Introduction

  • Example of Lewis Acid-Base Reaction:

    • Reaction: NH3 + H2O → NH₄⁺ + OH⁻

    • Here, NH3 acts as a base and H2O acts as an acid.

The Lewis Theory 2

Examples of Lewis Acids

  • Example: BF3 is an established strong Lewis acid.

  • Specific Reaction Involvement: Analyze BF3 interaction with NH3 (additional details noted in supplemental material).

The Preparation of Acids 1

Binary Acid Preparation

  • General Reaction: Binary acids are produced through the reaction of nonmetallic elements with hydrogen gas.

    • Reaction Example: H2(g) + Cl2(g) → 2HCl(g) (requires UV light for reaction to occur).

The Preparation of Acids 2

Volatile Acids

  • Production Method: Prepared by reacting salts with nonvolatile acids like sulfuric or phosphoric acid.

    • Specific Examples:

    • NaCl(s) + H2SO4(conc.) → NaHSO4(s) + HCl(g)

    • NaF(s) + H2SO4(conc.) → NaHSO4(s) + HF(g)

The Preparation of Acids 3

Preparing HBr and HI

  • Reaction Requirement: Use phosphoric acid for the production of these acids.

    • Example Reactions:

    • NaBr(s) + H3PO4(conc.) → NaH2PO4(s) + HBr(g)

    • NaI(s) + H3PO4(conc.) → NaH2PO4(s) + HI(g)

The Preparation of Acids 4

Ternary Acids

  • Preparation Method: Ternary acids are formed by the reaction of nonmetal oxides (acid anhydrides) with water.

    • Reaction Examples:

    • SO2(g) + H2O(l) → H2SO3(aq)

    • N2O5(g) + H2O(l) → 2 HNO3(aq)

  • Combined Reactions: Nonmetal halides and oxyhalides can yield both binary and ternary acids upon reaction with water.

    • Specific Reaction Examples:

    • PCl5(s) + 4 H2O(l) → H3PO4(aq) + 5 HCl(aq)

    • POCl3(l) + 3 H2O(l) → H3PO4(aq) + 3 HCl(aq)