competency explanation
Titration is a lab technique used to determine the concentration of an unknown solution by gradually adding a solution of known concentration until a reaction occurs, often indicated by a color change. In this lab, we used titration to figure out the concentration of hydrochloric acid (HCl) by adding sodium hydroxide (NaOH). We set up a burette with NaOH and a flask with HCl and phenolphthalein. The goal was to find out how much NaOH we needed to add to completely react with the acid. The endpoint of the titration was reached when the solution turned a very faint pink that lasted for about 30 seconds. We knew we were close to the endpoint when the pink color didn’t disappear quickly. To avoid adding too much NaOH, we used half drops near the endpoint. If we added too much, the solution turned very pink. In our first test trial, we used 14.15mL of NaOH, starting with 2.56mL, we ended with a light pink shade, so we adjusted in the second trial. We used slower half drops and reached a better endpoint at 13.41 mL. In the third trial, we got 13.63mL, but the trials didnt agree within a +- 0.1 mL with each other. After adjusting, we got a better result with the right color on trial 4, 13.76mL and an average of 0.137M +- 1.7%.
core competency reflection
In this lab, I used communication and critical thinking skills. I worked closely with my partner and talked to my peers to make sure we were doing things correctly. I also asked a few questions to the teacher whenever i was unsure if our results were correct. I used critical thinking by looking at the data we collected and using it to draw conclusions. For example, after seeing the results from the first trial, and properly knowing how to do full/half drops I knew that for the second and third trials, we could pour 10.00 mL of NaOH into the HCl without worrying about the solution turning dark or having a misreading.
