Lecture 142/21/07

Metal hydrolysis Heavy metals as Lewis acids Fe(H 2 O) 6 3+ (aq) ⇆ Fe(H 2 O) 5 (OH) 2+ (aq) + H + (aq) Fe(H 2 O) 6 2+ (aq) ⇆ Fe(H 2 O) 5 (OH) + (aq) + H + (aq)

Amphoteric metals (Al 3+, Cr 3+, Zn 2+, Sn 4+ ) Al(H 2 O) 3 (OH) 3 (s) - insoluble Al(H 2 O) 3 (OH) 3 (s) + OH - → Al(H 2 O) 2 (OH) 4 - (aq) + H 2 O Al(H 2 O) 3 (OH) 3 (s) + H 3 O + → Al(H 2 O) 4 (OH) 2 + (aq) + H 2 O

Table 16-5, p.800

How does changing pH affect solubility? Mg(OH) 2 (s) ⇄ Mg 2+ (aq) + 2OH - (aq) CaCO 3 (s) ⇄ Ca 2+ (aq) + CO 3 2- (aq) AgCl (s) ⇄ Ag + (aq) + Cl - (aq)

Determine the maximum concentration of Mn 2+ in a solution with a pH = K sp = 4.6 x

Molecular structure and acid strength Why do some compounds donate H + and some don’t? All acidic H bonds are polar bonds

Binary Acids  Within group:  Across Row: Molecular structure and acid strength

H-O-Z HOClHOBrHOI KaKa 3.5 x x x electronegativityCl (3.0)Br (2.8)I (2.5) Oxoacids with different central atoms