1. The problem statement, all variables and given/known data Methyl red has the following structure [not listed here on this post] Ka = 5.0 * 10 E -5 It undergoes a color change from red to yellow as a solution gets more basic. Calculate an approximate pH range for which the methyl red is useful. What is the color change and the pH at the color change when a weak acid is titrated with a strong base using methyl red as an indicator? For which of these two types of titrations is methyl red a possible indicator? 2. Relevant equations Henderson Hasselbalch equation 3. The attempt at a solution OK. I tried to figure this problem out, but I have no idea if I am right or not. If anybody could check, that would be great. Thanks. For the approximate pH range: For the pH range, I took the pH range to be within range of pKa plus/minus 1. So did: -log(5.0 * 10E-6) and then I added and subtracted 1. I got the answer to be [4.30, 6.30] For the weak acid with strong base titrated: Color changes from red to yellow. Then, the pH at the color change will be [second bullet] pH = pKa + log( [In-] / [HIn] ) = -log (5.0 E -6) + log ( 1/10 ) = 4.30 For the weak base titrated with strong acid: Color change: yellow to red pH? I did the same thing as in the previous step only my log expression had log(10/1) . I got my pH to be 6.30. For which of these two types of titrations is methyl red a possible indicator? The methyl red is a possible indicator for the weak base and strong acid titration. Any input on whether my solutions are right or not are greatly appreciated. Thanks in advance!