Definitions of acids and bases

Arrhenius Definition Acids – substances that produce H+ ions in solution. Ex: HCl, H2SO4, HBr Bases – subtances that produce OH- ions in solution Ex: NaOH, Mg(OH)2, LiOH

Bronsted Lowry Definition Acid – proton (H+) donors, they give H+ ions to a base. Base – proton (H+) acceptors, they accept H+ ions from an acid Form conjugate acid/base pairs Ex: NH3 + H2O  NH4+ + OH-

Practice 1. Which of the following are Arrhenius acids? Circle all that meet the definition. H2S NaOH KCl Ba(OH)2 HClO3 Li2CO3 HF H2O 2. Which of the following are Arrhenius bases? Circle all that meet the definition.

Practice 3. In the following equation, what are the acids? HCl + H2O  H3O+ + Cl- 4. In the following equation, what are the bases? H2PO4- + H2O  H3PO4 + OH-

The pH and pOH scales

pH scale Measures the amount of H+ in a solution. Scale used to measure whether a substance is an acid or a base. Lower numbers are acids. Higher numbers are bases

Examples Which of the following pH values represents the strongest acid? A) 12.0 B) 9.0 C) 2.0 D) 7.0 Which of the following pH values represents the weakest base?

pOH scale pH + pOH = 14 Measures the amount of OH- in a solution. The pH and pOH scales are related by the following equation. pH + pOH = 14 Ex: What is the pOH of a solution if its pH is 4? Is it an acid, base, or neutral? Ex: What is the pH of a solution if the pOH is 9?

Strong Acids/Bases Completely dissociate (break apart) in water. Excellent conductors of electricity. Highly corrosive. Some common strong acids -HCl, H2SO4, HClO4 Some common strong bases – NaOH HA H+ A-

Neutralization HCl + NaOH  NaCl + H2O When a strong acid and a strong base are mixed together, it has 2 products: A neutral salt Water Ex: HCl + NaOH  NaCl + H2O strong acid strong base salt water