Chapter 34, Problem 1ASA

You are given four different aqueous solutions and told that they each contain NaOH, Na2CO3, NaHCO3, or a mixture of these solutes. You do some experiments and gather these data about the samples. Sample A: Phenolphthalein is colorless in the solution. Sample B: The sample was titrated with HCl until the pink color of phenolphthalein disappeared, then methyl orange was added. The solution became pink. Methyl orange changes color from pH 3.01 (red) to pH 4.4 (orange). Sample C: Equal volumes of the sample were titrated with standardized acid. Using phenolphthalein as an indicator required 15.26 mL of standardized acid to change the phenolphthalein color. The other sample required 17.90 mL for a color change using methyl orange as the indicator. Sample D: Two equal volumes of the sample were titrated with standardized HCl. Using phenolphthalein as the indicator, it took 15.00 mL of acid to reach the equivalence point; using methyl orange as the indicator required 30.00 mL HCl to achieve neutralization. Identify the solute in each of the solutions.

A solution contains Ca2+ and Pb2+ ions, both at a concentration of 0.010 M. You wish to separate the two ions from each other as completely as possible by precipitating one but not the other using aqueous Na2SO4 as the precipitating agent. (a) Which will precipitate first as sodium sulfate is added, CaSO4 or PbSO4? (b) What will be the concentration of the first ion that precipitates (Ca2+ or Pb2+) when the second, more soluble salt begins to precipitate?

You have a solution that contains AgNO3, Pb(NO3)2, and Cu(NO3)2. Devise a separation method that results in having Ag+ in one test tube, Pb2+ in another, and Cu2+ in a third test tube. Use solubility guidelines and Ksp and Kf values.