Chapter 15, Problem 123QRT

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.