Phenolphthalein has a pKa of 9.7. It is colorless in its acid form and pink in its basic form. For each of the following pH values, determine whether [In-] > [HIn] and predict the color of a phenolphthalein solution: a. pH = 2.0 b. pH = 5.0 c. pH = 8.0 d. pH = 11.0

Verified step by step guidance

1. <insert step 1: Understand the relationship between pH, pKa, and the color change of phenolphthalein. Phenolphthalein changes color based on the ratio of its ionized form [In^-] to its non-ionized form [HIn].>
2. <insert step 2: Use the Henderson-Hasselbalch equation: pH = pKa + log([In^-]/[HIn]). This equation helps determine the ratio of [In^-] to [HIn] at a given pH.>
3. <insert step 3: For each pH value, compare it to the pKa of phenolphthalein (9.7) to determine the dominant form. If pH > pKa, [In^-] > [HIn]; if pH < pKa, [HIn] > [In^-].>
4. <insert step 4: a. For pH = 2.0, since 2.0 < 9.7, [HIn] > [In^-], so the solution is colorless.>
5. <insert step 5: b. For pH = 5.0, since 5.0 < 9.7, [HIn] > [In^-], so the solution is colorless.>