CH 10 - Acids and Bases and Equilibrium (1)

Definition of Acids and Bases

  • Acid: Derived from the Latin word acidus, meaning "sour".

  • Base: Opposes the properties of an acid, often defined as a substance that can accept protons (H⁺).

Bronsted-Lowry Acids and Bases

  • Bronsted-Lowry Acid: A substance that donates H⁺ ions.

  • Bronsted-Lowry Base: A substance that accepts H⁺ ions.

Conjugate Acid-Base Pairs

  • Every acid-base reaction involves pairs of conjugate acids and bases related by the gain or loss of a proton (H⁺).

  • Example: In the reaction between NH₃ and H₂O, NH₃ is the base and H₂O is the acid, forming the conjugate acid H₃O⁺ and conjugate base OH⁻.

Strong Acids to Memorize

  • Hydrochloric Acid (HCl)

  • Hydrobromic Acid (HBr)

  • Hydroiodic Acid (HI)

  • Sulfuric Acid (H₂SO₄)

  • Perchloric Acid (HClO₄)

  • Nitric Acid (HNO₃)

Le Châtelier’s Principle

  • States that when a system at equilibrium is subjected to a stress, the system shifts in a direction that counteracts the stress.

Ionic Product Constant of Water

  • ext{The relationship is represented as:} Kw=[H3O+][OH−]=1.0imes10−14K_w = [H_3O^+][OH^-] = 1.0 imes 10^{-14}

  • Neutral Solution: If   [H3O+]=[OH−][H_3O^+] = [OH^-]

  • Acidic Solution: If   [H_3O^+] > [OH^-]

  • Basic Solution: If   [OH^-] > [H_3O^+]

pH Definition and Calculations

  • pH: A measure of how acidic or basic a solution is, defined as   pH=−extlog[H3O+]pH = - ext{log}[H_3O^+]

  • To calculate pH from known   [H3O+][H_3O^+]:   pH=−extlog[H3O+]pH = - ext{log}[H_3O^+]

  • To find   [H3O+][H_3O^+] from pH:   [H3O+]=10−pH[H_3O^+] = 10^{-pH}

Buffer Solutions

  • Components of Buffers: Typically consist of a weak acid and its conjugate base, or a weak base and its conjugate acid.

  • How Buffers Work: Buffers maintain a relatively constant pH when small amounts of an acid or base are added by neutralizing the added acids or bases.