© University of South Carolina Board of Trustees pH  K a The pH of a M solution of HNO 2 is Calculate K a for the acid.

© University of South Carolina Board of Trustees K a  pH Calculate the pH of a M CH 3 COOH (acetic acid) solution. K a = 1.80 x10 −5.

© University of South Carolina Board of Trustees Chapt. 15 Acids and Bases Sec. 6 Weak Bases

© University of South Carolina Board of Trustees Strong vs Weak Strong Acids HA + H 2 O  A − (aq) + H 3 O + (aq) 0% goes to completion Weak Acids HA + H 2 O  A − (aq) + H 3 O + (aq) 99+%partial ionization equilibrium Strong Bases BOH  B + (aq) + OH − (aq) 0% goes to completion Weak Bases B + H 2 O  BH + (aq) + OH − (aq) 99+% or BOH  B + (aq) + OH − (aq)

© University of South Carolina Board of Trustees Define K a and K b HA (aq) + H 2 O (l)  A − (l) + H 3 O + (aq) B (aq) + H 2 O (l)  HB + (l) + OH − (aq) no solvent acid on left 1 mole acid base on left 1 mole base

© University of South Carolina Board of Trustees K b  pH Calculate the pH of a solution of M methylamine (CH 3 NH 2 ), if K b = 4.4 x10 −4 M.

© University of South Carolina Board of Trustees Chapt. 15 Acids and Bases Sec. 6 Weak Acid-Base Conjugates

Acid / Base vs Conjugate © University of South Carolina Board of Trustees Good Acid  Poor Conj. Base Poor Acid  Good Conj. Base K a K b = K w

© University of South Carolina Board of Trustees K a K b = K w

Acid / Base vs Conjugate © University of South Carolina Board of Trustees Strong Acid  Spectator Ion Good Acid  Poor Conj. Base Poor Acid  Good Conj. Base Spectator Ion  Strong Conj. Base K a K b = K w

© University of South Carolina Board of Trustees Spectator Ions (Memorize) No Effect on pH Conjugate of Strong Acid or Strong Base Strong acids  Cl −, I −, Br −, ClO 4 −, NO 3 −Strong acids  Cl −, I −, Br −, ClO 4 −, NO 3 − Strong bases  Li +, Na +, K +, Rb +, Cs + Mg 2+, Ca 2+, Sr 2+, Ba 2+Strong bases  Li +, Na +, K +, Rb +, Cs + Mg 2+, Ca 2+, Sr 2+, Ba 2+

© University of South Carolina Board of Trustees Student Example For each compound, is an aqueous solution acidic (pH 7)? Ca(NO 3 ) 2 Ca(NO 2 ) 2 NH 4 Br Li(HCOO) (CH 3 NH 3 )I (cocaine·H)Cl neutral basic acidic cocaine