Acids and Bases Review

Acid Nomenclature

• Binary Acid:
  • Composed of hydrogen and one other element.
  • Named using the "hydro-" prefix, followed by the element's root name, the "-ic" suffix, and "acid".
  • Example: HCl is hydrochloric acid.
• Oxyacid:
  • An acid containing a polyatomic ion that includes oxygen.
  • If the polyatomic ion ends in "-ite," the acid name uses the "-ous" suffix.
  • If the polyatomic ion ends in "-ate," the acid name uses the "-ic" suffix.
  • The word "acid" is added at the end.
  • Examples:
    • HClO: hypochlorous acid (from ClO^- hypochlorite ion)
    • HClO2: chlorous acid (from ClO2^- chlorite ion)
    • HClO3: chloric acid (from ClO3^- chlorate ion)
    • HClO4: perchloric acid (from ClO4^- perchlorate ion)

Practice

• Name the following acids:
  • HF
  • H2SO4
  • HNO_3
  • H_2S
  • H2PO4

Definitions of Acid/Base

• [H^+] = concentration of H^+ ions, [ ] = concentration
  • Arrhenius Definition
    • Acid: A compound that increases the H^+ ion concentration in aqueous solution (H+ donor).
      • Example: HCl dissociates into H^+ and Cl^- in water.
    • Base: A compound that increases the OH^- ion concentration in aqueous solution (OH^- donor).
      • Example: NaOH dissociates into Na^+ and OH^- in water.
  • Neutralization: The reaction between an acid and a base to form a neutral product.
    • Neutralization of Arrhenius acids and bases forms salt and water (H_2O).
    • Example: HCl(aq) + NaOH(aq) \rightarrow NaCl(aq) + H_2O(l)
  • Limitations: Not all acids and bases fit the Arrhenius definition.
    • Example: NH3 in water forms a basic solution: NH3 + H2O \rightarrow NH4^+ + OH^-
  • Bronsted-Lowry Definition
    • Acid: A proton (H^+) donor.
      • A proton (H^+) is essentially a hydrogen atom without its electron.
    • Base: A proton acceptor.
      • Example: C6H6O + NH2^- \rightarrow C6H5O^- + NH3
        • C6H6O loses H^+ (proton donor) = acid
        • NH_2^- gains H^+ (proton acceptor) = base
  • Reversible Reactions: Many acid-base reactions are reversible.
    • Example: NH3 + H2O \rightleftharpoons NH_4^+ + OH^-
      • Forward reaction: NH3 is the base, H2O is the acid.
      • Reverse reaction: NH_4^+ is the acid, OH^- is the base.
    • Conjugate Acid/Base Pairs:
      • NH3/NH4^+ and H_2O/OH^-
      • NH3 is the base, NH4^+ is the conjugate acid.
      • H_2O is the acid, OH^- is the conjugate base.
  • Examples
    • Arrhenius acid/base
      • Ca(OH)2 + H2SO_4 \rightleftharpoons
    • Bronsted-Lowry acid/base
      • H3PO4 + H2O \rightleftharpoons H3O^+ + H2PO4^-
  • Water as Solvent
    • Water is a common solvent for acid/base reactions
    • Not all acid/base reactions involve water, H^+ , or OH^-
    • Not all acid/base reactions produce 2 products
  • Lewis Definition
    • Acid: Electron acceptor.
    • Base: Electron donor.
    • General reaction: A^+ + B^- \rightarrow A-B
      • A (acid) charge decreases (more negative).
      • B (base) charge increases (more positive).
    • Example: NH3 + BF3 \rightarrow BNH3F3

Autoionization of Water

• Many neutralization reactions are reversible
• H_2O \rightleftharpoons H^+ + OH^-
  • Water can separate into ions
  • Pure water contains \left[H^+\right] = 1 \times 10^{-7} M and \left[OH^-\right] = 1 \times 10^{-7} M
  • pH = 7 and pOH = 7
  • Formula: \left[H^+\right] = 10^{-pH}

pH Scale

• Measures the acidity or basicity of a solution in water.
  • Neutral: pH = 7
  • Acidic: pH < 7 (high H^+ concentration)
  • Basic: pH > 7 (low H^+ concentration)
    • The pH scale is generally considered to range from 0 to 14, but it can be < 0 or > 14.

Exponential Functions

• f(x) = 2^x = 1 \cdot 2^x
  • 2 = rate of growth (doubling each time)
  • x = number of times it grows by 2
  • 1 = initial amount (100% or 1).
• f(x) = how much something changes after x number of times.
  • f(0) = 1 \cdot 2^0 = 1 \cdot 1 = 1
    • Initial amount (100%) before any change.
  • f(1) = 1 \cdot 2^1 = 1 \cdot 2 = 2
    • Amount after doubling once.
  • f(2) = 1 \cdot 2^2 = 1 \cdot 4 = 4
    • Amount after doubling twice.
• Negative Exponents:
  • f(-1) = 1 \cdot 2^{-1} = \frac{1}{2^1} = \frac{1}{2}
    • Amount before it doubled once.
  • f(-2) = 1 \cdot 2^{-2} = \frac{1}{2^2} = \frac{1}{4}
    • Amount before it doubled twice.
  • f(-3) = 1 \cdot 2^{-3} = \frac{1}{2^3} = \frac{1}{8}
    • Amount before it doubled three times.

Logarithms

• Exponential function: b^x = y
  • b = base
• Logarithmic function: \log_b(y) = x
  • x and y are switched (inverse of exponential function).
• Meaning:
  • b^x = y
    • y = how much if it changes by rate ‘b’ for ‘x’ number of times
  • \log_b y = x
    • x = how many times it changes by rate ‘b’ to get to ‘y’

pH, pOH, and Concentration Calculations

• \left[H^+\right] = 10^{-pH}
• pH = -\log_{10}\left[H^+\right]
• \left[OH^-\right] = 10^{-pOH}
• pOH = -\log_{10}\left[OH^-\right]
• \left[H^+\right] \cdot \left[OH^-\right] = 10^{-14} M
• pH + pOH = 14

Practice Problems

• If the pH of a solution is 2.46, solve for:
  • \left[H^+\right]
  • pOH
  • \left[OH^-\right]
• If \left[OH^-\right] = 1.35 \times 10^{-5} M, solve for:
  • pH
  • \left[H^+\right]
  • pOH

pH Warmup