Properties of Acids Taste sour pH < 7 Turn litmus red Colorless with phenolphthalein Neutralize bases React with metals to produce H 2 gas React with carbonates to produce CO 2, H 2 O, and a salt.

Properties of Bases Taste bitter pH > 7 Turn litmus blue Bright pink with phenolphthalein Neutralize acids Dissolve wool Feel slippery

Acid Base Definitions Originally recognized by properties like taste, feel, reactions with indicators

Arrenhius Definition Acids produce excess Hydrogen ions when added to water Bases produce excess Hydroxide ions when added to water Issues: – Very limited definition – Very few substances can actually be classified by this definition.

Bronsted-Lowry Definition Acids are proton victims, “donors” – The molecule loses an H + Bases are proton thieves, “acceptors” – Steal an H + from another molecule More frequently used

Conjugate base Ion that is formed when an acid donates a Hydrogen ion (proton) Examples:AcidConjugate base H 2 SO 4 HSO 4 1- HNO 3 NO 3 1- HC 2 H 3 O 2 C 2 H 3 O 2 1-

Conjugate base If original acid is a strong acid, the conjugate base is so weak that is does not behave as a base. – It behaves as a neutral species If original acid is a weak acid, the conjugate base behaves as a weak base (Important for equilibrium considerations later)

Conjugate acid Ion that is formed when a base accepts a Hydrogen ion Examples:BaseConjugate acid NaOHH 2 O NH 3 NH 4 1+

Conjugate acid If original base is a strong base, the conjugate acid is so weak that is does not behave as an acid. – It behaves as a neutral species If original base is a weak base, the conjugate acid behaves as a weak acid

Amphoteric Substances A species that can behave as either an acid or a base Water is the best example of an amphoteric substance

Strong Acids Acid that dissociates completely in water 100% of the sample breaks apart into ions Six strong acids: 1. HCl- Hydrochloric acid 2. HBr- Hydrobromic acid 3. HI- Hydroiodic acid 4. HNO 3 - Nitric acid 5. H 2 SO 4 - Sulfuric acid 6. HClO 4 - Perchloric acid *HClO 3 - Chloric acid is borderline

Strong Base Base that dissociates completely in water 100% of the sample breaks apart into ions Strong bases – Hydroxides of the metals in group 1A and 2A (not Be or Mg)

Weak acid or weak base Do NOT dissociate completely in water In water, establishes equilibrium between the molecular form and ionic form Any acid or base that is not a strong acid or base is weak Example: Acetic acid HC 2 H 3 O 2 + H 2 O  C 2 H 3 O H 3 O 1+

Autoionization of water The transfer of a hydrogen ion from one water molecule to another water molecule, – results in the formation of a hydroxide ion and a hydronium ion. Equation:2 H 2 O  H 3 O 1+ + OH 1- Equal amounts of hydroxide and hydronium are formed, – so water remains neutral.

pH system The pH of a system is an indication of the [H 3 O 1+ ]. While it is based on the autoionization of water, it works for all acid- base systems.

pH system Definitions: pH = -log [H 3 O 1+ ] pOH = -log [OH 1- ] pK w = -log K w Since K w = 1.0 x , pK w = -log (1.0 x ) = 14 K w = [H 3 O 1+ ] [OH -1 ]  pK w = pH + pOH = 14

pH Strong Acids and Bases [H 3 O 1+ ] = initial concentration of acid – To find the pH of a strong acid, use the initial concentration of the acid as the concentration of H 3 O 1+ [OH 1- ] = initial concentration of base pH (strong acid) = -log (initial conc.)