Classifying Acids and Bases

Acid and Base Theories  There are different ways of defining what an acid and base is 1. Arrhenius 2. Bronstead Lowry

1. Arrhenus acids and bases in solution  Arrhenius Acid: Chemical compound that increases concentration of hydrogen ions H+  Compounds containing hydrogen  H 2 SO 4  Arrhenius Base: Chemical compound that increases concentration of hydroxide ions (OH-)  Compounds contain hydroxides  NaOH

 Issue: Arrhenius acids/bases must be in solution, but scientists found that some substances acted as acids or bases when they were NOT in a water solution so the definition had to revised…  Not all acids have H, not all bases have OH

2. Bronstead-Lowry Acids and bases  Bronstead Lowry Acids: A molecule or ion that is a proton donor  Bronstead Lowry Bases: A molecule or ion that is a proton acceptor **Hydrogen is a proton!!

Bronstead Lowry Reactions  Acid + Base → conjugate base + conjugate acid  Conjugate Base: The remainder of an acid after H + is released  Conjugate Acid: The base formed by accepting a proton

Label the following molecules as acid, base, conjugate acid, conjugate base  Look at where the hydrogens are going!! HCl + H 2 O → Cl - + H 3 O + HNO 3 + OH - → H 2 O + NO 3 -

TypeAcidBase ArrheniusH+ donorOH- donor Bronsted-LowryProton (H+) donor Proton (H+) acceptor

Strong acids  STRONG acids and bases are considered to completely ionize in aqueous solution.  Good conductors of electricity  Strong acids (memorize) HCl, HBr, HI, HNO 3, H 2 SO 4, HClO 3

Strong bases  Strong bases: Group 1 and 2 metal Hydroxides (not Be or Mg)  EX: NaOH, Ba(OH) 2 Ca(OH) 2 LiOH, KOH…and NH 3

All other acids/bases are considered WEAK WEAK acids and bases only partially ionize in water (aqueous solution)

1. Monoprotic acids- acids donating 1 hydrogen Ex: HCl, HF, HNO 3 2. Diprotic acids- acids donating 2 hydrogens Ex: H 2 SO 4, H 2 CO 3 3. Triprotic acids- acids donating 3 hydrogens Ex: H 3 PO 4