If you run out, you will need to standardize more of these solutions . If NaOH has been added with a buret, its volume V NaOH , is known and the concentration of NaOH is found using Equations 7 and 8. The color change occurs over the pH range of 8.0-9.8 and actual color will depend on the concentration. Because the color is so intense, only a very small amount of indicator is added so that it only slightly affects the equilibrium. The endpoint is taken at the first stable pink color.
Indicators always react with one of the reagents.
The titrated form of the indicator is intensely red, so the solution turns red as NaOH is added beyond the equivalence point. The titration is stopped at the end point, which is slightly beyond the equivalence point. Obtain a sample of pure KHP from the dispensing area. Using a rough balance, shake about 2 grams into a clean, dry, weighing bottle. Do NOT insert anything into the dispensing bottles of KHP .