Chapter 9

Chapter 9 Overview

• Learning Changes Everything.®

• Prepared by: Andrea Leonard, University of Louisiana at Lafayette

• Copyright 2022 © McGraw Hill LLC.

Symbols in Chemical Equations

• Symbol Meanings:

  • +: separates reactants/products

  • →: "yields" or "produces"

  • ⇌: equilibrium arrow

  • (g): gaseous state

  • (s): solid state

  • (aq): aqueous (dissolved in water)

  • Δ: indicates heat applied

Arrhenius Acids and Bases

• Arrhenius Acid: Provides H+ in water (e.g., HNO3 → H+ + NO3-)

• Arrhenius Base: Provides OH- in water (e.g., KOH → K+ + OH-)

Brønsted Acids and Bases

• Brønsted Acid: Donates a proton (H+)

• Brønsted Base: Accepts a proton (H+)

• Example: HNO2 + H2O ⇌ H3O+ + NO2-

Conjugate Acids and Bases

• Conjugate Acid: Species formed when a Brønsted base accepts a proton.

• Conjugate Base: Species remaining when a Brønsted acid donates a proton.

Self-Ionization of Water

• Equal Concentrations: In pure water: [H3O+] = [OH-] = 1.0×10–7 M

• Neutral Solution: pH 7, equal amounts of H3O+ and OH-.

pH Concept

• pH: Negative logarithm of H+ concentration.

  • Formula: pH = -log[H3O+]

• Neutral pH: 7

• Acidic: pH < 7; Basic: pH > 7

Acid-Base Strengths

• Strong Acids/Bases: Completely ionize in solution.

• Weak Acids/Bases: Partially ionize in solution.

Buffers

• Definition: Solutions that resist pH changes; usually a mix of acid and its salt (e.g., carbonic acid and bicarbonate).

Molarity and Osmolarity

• Molarity (M): Moles of solute per liter of solution.

  • Example: 0.134 moles in 0.250 L = 0.536 M

• Osmolarity (mOsm): osmoles of solute per liter of solvent.

Tonicity

• Hypertonic: Higher osmolarity.

• Isotonic: Equal osmolarity.

• Hypotonic: Lower osmolarity.

Calculating Osmolarity

• Example Calculation:

  • 1.008 mol of glucose in 4 L of water = 0.252 mOsm.

  • 114.5 g of KCl in 3.6 L of solution = (number of particles based osmolarity calculation).