Use the solubility-product constant for Cr(OH)₃ (K_sp = 6.7 × 10^-31) and the formation constant for Cr(OH)₄ from Table 17.1 to determine the concentration of Cr(OH)₄ in a solution that is buffered at pH = 10.0 and is in equilibrium with solid Cr(OH)₃.

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Formation Constants for Some Metal Complex lons in Water at 25 °C Complex Ion K; Equilibrium Equation Ag(NH3),* Ag(CN)2 Ag(S,O3),3- CdBr,- Ag" (aq) + 2 NH3(aq) = Ag(NH3)2*(aq) Ag*(aq) + 2 CN (aq) Ag(CN)2 (aq) Ag*(ag) + 2 S203 (aq) = Ag(S,03)2 (aq) Cd2+(aq) + 4Br (aq) Cr*(aq) + 4OH (aq) Cr(OH), (aq) Co2+(aq) + 4 SCN (aq) Cu2+(aq) + 4 NH3(aq) Cu2+(aq) + 4 CN (aq) = 2+(aq)+6 NH3(aq) 1.7 X 107 Ag(NH3),*(aq) 1 × 1021 2.9 x 1013 Ag(S,O3)2 (aq) 5 x 103 CdBr, (aq) Cr(OH)4 8 X 1029 Co(SCN),- Cu(NH3),+ Cu(CN), Ni(NH3),+ Fe(CN),- Fe(CN), 1 x 103 5 x 1012 1X 1025 Co(SCN), (aq) Cu(NH3),*(aq) Cu(CN), (aq) 2+ 2- Ni²* (aq) + 6 NH3(aq) = Ni(NH3),*(aq) Fe"(aq) + 6 CN (aq) = Fe(CN3), (aq) Fe (aq) + 6 CN (aq) 1.2 X 10° 1 X 1035 1 X 1042 4- 3- = Fe(CN), (aq)