Acids & Bases

Aqueous solutions (aq) ~60% of the human body is water Most chemical reactions inside our body require water or occur in a water solution When a solid is dissolved in water, the water allows the solid atoms to move around and react easier

Properties of Acids Taste sour Turn blue litmus paper red solutions conduct electricity React with certain metals to produce hydrogen gas React with carbonates (CO3) to produce carbon dioxide

Properties of Bases Taste bitter Feel slippery Turn red litmus paper blue Produce solutions that conduct electricity

Arrhenius Definition Acid Base Substance that contains hydrogen and produces hydrogen ions (H+) in aqueous solutions HCl  H+ + Cl- Base Contains a hydroxide group (OH) and dissociates to produce hydroxide ions in aqueous solutions NaOH  Na+ + OH-

Practice Problem 1 Based on their formulas, which of the following compounds may be Arrhenius acids: CH4, SO2, H2S, Ca3(PO4)2 Explain your reasoning.

Bronsted-Lowry Definition Acid Hydrogen ion donor HCl + H2O  H30+ + Cl- Base Hydrogen ion acceptor NH3 + H2O  NH4+ + OH-

Acids, Bases or Neutral All water (aqueous) solutions contain hydrogen ions (H+) and hydroxide ions(OH-) The amounts of the two ions determine whether a solution is acidic, basic or neutral

Acidic solution Basic solution Neutral solution H+ > OH- OH- > H+ Neutral solution H+ = OH-

Acid – Base Reactions Special type of reaction that occurs in aqueous solutions (water) Acid and base are reactants Proton (H+) transfers from acid to base

Conjugate Acid- Base Pairs Two substances related to each other by the donating and accepting of a single hydrogen ion Example: HCl + H2O  H30+ + Cl-

Practice Problem 2 Determine the acid-base conjugate pairs for the following chemical reaction: H3PO4 + H2O  H3O+ + H2PO4-

Amphoretic Substances that can act as both an acid and a base Examples: Water HCl + H2O  H30+ + Cl- NH3 + H2O  NH4+ + OH-