I expect the solution to be purple pink because phenolphthalein turns purple/pink when the solutions pH is greater than 7. If the concentration of the HCl is greater than the equivalent point, then the solution will be transparent/clear. 7. Suppose you titrated a sample of acetic acid (monoprotic acid) with a 0.125 M solution of NaOH. Given the data in the table below, what is the concentration of the acetic acid solution? Show all work including units to receive full credit. Volume of 0.125 M NaOH dispensed 22.40 mL Volume of acetic acid solution used 15.00 mL Volume of water added to the HCl solution 15.00 mL 0.125M*22.40mL= 2.8mmol of NaOH 2.8mmol/15mL=.18667M
Conclusions: Your conclusion should include the following: 1. What did you learn from this experiment? Base your conclusions on experimental observations. 2. A proper conclusion connects the experiment (data, observations, and calculations) results back to key principle(s) stated in the background section. This should be 2-3 paragraphs. Write your conclusion below. The purpose of this lab was to try and pinpoint the exact moment when a solution (in this case the HCl) reaches titration. The indicator for this experiment was phenolphthalein. This indicator is colorless when it is in the presence of an acid and when it is in the presence of a base it turns pink/purple. Phenolphthalein was a perfect indicator for this experiment because it changes color when the pH becomes close to the equivalence point. When the solution becomes basic (meaning it has a pH greater than 7) the phenolphthalein turns purple/pink. One very important thing in this experiment was the monitoring of the titrator, adding the titrator too fast would cause me to miss the exact point of titration so it was imperative that I take my time adding the NaOH (the titrator/titrant) to the analyte (the HCl). My data shows that the exact point of titration is not easy to pinpoint but being patient when adding the titrator helps. In experiment one, I found my coarse titration point to be approximately when 11.45ml of the NaOH was added to the solution. In this experiment I was holding the knob to release the titrator without caring how much I was adding and simply waiting for the color to change, but because the titration point is very sensitive in order to try and record my fine titration I had to redo this experiment a few times. In my trial 1 for my fine titration I found that the solution’s color became basic/
turned pink purple when 11.35ml of the titrator was added and in trial two titration was reached once 11.30ml of the titrator was added. I was fascinated by the power that the indicator (phenolphthalein) holds in the titration process. I wanted to see for myself what would happen if the indicator was left out would the solutions color change at all and based on my results of the solution remaining clear I was able to conclude that the indicator is indeed the game changer for the analyte. I added the complete 50mL of NaCl to the HCl and absolutely nothing about the color of the solution was altered.
- Fall '09