Question

Below is a Ksp Table of many common hydroxides used frequently in chemistry. If you were given a set of ions to convert to hydroxides, which 2 ions would be the easiest to separate? a) Cobalt and Iron b) Magnesium and Calcium c) Nickel and iron d) Cobalt and Calcium e) Copper and Zinc Circle the above pair and explain your reasoning: Al(OH)3 Cd(OH) Ca(OH)2 Cr(OH)3 CO(OH) 3 Co(OH)2 Cu(OH) 2 Fe(OH), Fe(OH) 2 Pb(OH)2 Mg(OH)2 Mn(OH) 2 Ni(OH) 2 Zn(OH)2 4x 1015 2 x 10 6x 106 7 x 1031 1x104 3 x 1016 2 x 1019 6x 1038 2 x 10" 4 x 10-15 2 x 10 11 2 x 1013 2 x 10-16 5 x 10-17 Below is a chart showing the solubility of two common barium molecules. If you wanted to get the best possible separation of these two chemicals how would you do it. If needed, use the back of this page to discuss two main factors involved. • Ba(NO3)2 Ba(OH)2 Barium Detailed Solubilty plot y 1.628 R=0.9804 Solubility (mass %) y 0.2145x + 4,1065 R = 0.9986 40 50 60 70 80 Temperature (°C) 90 100 8.50 10 20 30

Answer 1

Cobal and calcium can be easily separated as the K_sp values for Co(OH)₃ is 10^-43 and that of Ca(OH)2 is 6X10^-6, this shows that the K_sp of Co(OH)₃ is much much less and so it will precipitate first.

The chart shows the solubility of two barium salts, and it clearly shows that with the rise in temperature the solubilities are increasing but for Ba(HO)2 the rise is sharp, so the substance which has less solubility will be precipitated first, so, at temperature of about 30⁰ C, Ba(NO₃)₂ will be precipitated first. To precipitate we shuld add dilute nitric acid in salts of barium