summary L2 Acid Base and Titration

Units of Concentration

  • A solution consists of a solute (substance dissolved) and a solvent (medium). Concentration = ratio of solute to solvent.

Percent Concentration

  • % (w/w), % (w/v), % (v/v):

    • % (w/w) = % Concentration x 100 (mass solute / mass solution)

    • % (w/v) = % Concentration x 100 (mass solute / volume solution)

    • % (v/v) = % Concentration x 100 (volume solute / volume solution)

Parts per Million and Billion

  • ppm = mass solute / volume solution x 10^6

  • ppb = mass solute / volume solution x 10^9

  • ng/L for ppt (parts per trillion).

Molarity and Molar Mass

  • Molarity (M) = moles of solute / L of solution;

  • Molar mass = grams/mole of a substance;

  • Calculate molar mass by summing individual element masses.

Solution Preparation

  • To prepare a stock solution: g = M x L x molar mass.

Dilutions

  • Dilution formula: C1V1 = C2V2; where C1 is stock concentration, C2 is diluted concentration, V1 is stock volume, and V2 is final volume.

Acid and Base Definitions

  • Arrhenius: Acid increases [H3O+], Base increases [OH-].

  • Brønsted-Lowry: Acid donates protons, Base accepts protons.

  • Lewis: Acid accepts electron pairs, Base donates electron pairs.

Strong vs Weak Acids and Bases

  • Strong acids ionize completely (e.g., HCl); weak acids partially ionize (e.g., HF).

  • Strong bases (e.g., NaOH) completely dissociate; weak bases (e.g., NH3) do not.

Conjugate Acids and Bases

  • Conjugate pairs: Acids donate protons; conjugate bases are what remains after donation.

Acid Strength

  • Ka used to express strength; strong acids have large Ka values.

Water's Ionization

  • Auto-ionization: 2H2O ⇌ H3O+ + OH-; Kw = [H3O+][OH-] = 1.0 x 10^-14 at 25°C.

pH Scale

  • pH = -log[H+];

  • Acidic: pH < 7, Neutral: pH = 7, Basic: pH > 7.

Titration and Neutralization

  • Titration determines concentration using standard solutions; equivalence point occurs when [H+] = [OH-].

  • Neutralization reaction: Acid + Base → Salt + Water.

Titration Problems

  • Use stoichiometry or the formula aM2V2 = bM1V1 to solve titration issues.

  • Typical examples involve finding unknown concentrations by balancing acid-base reactions.