Curricular Competency Explanation:
Cover the following points. This will take the place of a lab write-up conclusion.
- What is a titration?
- What was a titration used for in this lab?
- What is the endpoint (or the equivalence point) of a titration?
- How do you know that you have reached the endpoint of the titration?
- What were your results?
A titration is a technique used to determine the concentration of a substance in a solution. Titration relies on a known chemical reaction between the chemical of unknown concentration (analyte), and chemical of known concentration (titrant). The analyte is a measured volume of the solution, with an unknown concentration, while the titrant’s concentration is known, and is added drop by drop from a burette into the analyte (which often sits in a Erlenmeyer flask or beaker). In this titration lab (20C: Acid-Base Titration), a titration was used by putting 10.00mL HCl (hydrochloric acid) of an unknown molarity into an Erlenmeyer flask, adding 3 drops of phenolphthalein to it, then adding 0.10M NaOH (sodium hydroxide) drop by drop from a burette above. Each time even the slightest bit of NaOH made contact with the solution, it turned pink in that area, hence why one of the instructions while adding the NaOH was to constantly swirl the Erlenmeyer flask (to mix it in, therefore getting rid of the colour). As NaOH gets added, each drop became more colourful than the previous, and stayed longer. the Goal was to add a measured amount of NaOH until the solution obtained a slightly pink hue around its surface. This is the ideal point where the titrant added is stoichiometrically equivalent to the amount of analyte (in other words, when the moles of acid is equal to the moles of base, resulting in complete neutralization). The endpoint is when the solution gains its slight tint, as the teacher told us it should be. After four trials, only two of them gained their tint perfectly (while trial 1 and 2’s solutions lost their transparencies too much). As for the questions after the lab, students were asked to find the moles of NaOH in the solution by averaging the volume of it used throughout the trials, then to find the moles of HCl in the solution, then to find its molarity, thus being able to tell us the molarity of the original container of HCl.
Core Competency Reflection:
As stated in the above lab, although I have been given instructions on what to do, there were no instructions on the pacing of the lab. Since multiple trials had to be done, me and my partner agreed to see to it that the table of all 4 trials on our paper are filled in. The problem was that we clearly were being too hasty to the point we were wasting time since the data from different trials were not allowed to be used if outside of 0.05ml of each other. We were about to make the same mistake on the third trial, but I decided that the first time was just to know what we were doing, the second one was a genuine mess up (as identifying mistakes is in my nature before I proceed), but as pressure was starting to weigh on me seen as how much time we messed up with, I decided to do the titrations but this time, follow my own instinct and not rush it. We originally continued adding drops or streamlining too much NaOH, thinking that the swirling would be able to remove all the colour, but we were wrong twice. Although it seems like basic problem solving, it feels good to be able to remind myself like with this lab, that taking a step back, identify areas needed to be changed, yet having the time to advocate for my goals and intentions is still something I am able to do, (and well within my nature) even when I feel under pressure. My partner seemed to want to speed up, and as compensation for speeding up to cause errors, it seemed as though he planned on asking a teacher for help identifying quick mistakes, thinking that they are easy enough to realize and fix instantly. Although he was correct about being able to resolve it quickly, doing the titration the correct (slow) way with only an hour took time and he had to leave for the next block (and the lab would apparently be closed once our class is done). I volunteered to stay behind if needed, which put him at ease, allowing us to get 2 accurate trials. Volunteering to do things no matter the difficulty is both within my personality as a responsibility as someone with several younger cousins and have had to entertain several kids before, and also as a cultural part of my identity being a volunteer at mosques. Throughout the whole time though, I was certain that we would not need to stay longer anyways, and I was correct, as spending time to play it safe and slow would result in better results, making less of a mess to clean up and would ensure we can follow steps precisely, removing time spent needing to think or ask for help; just read and do. That certainty does not come from a “positive” or “optimistic” part of my personality. This has nothing to do with being positive, negative, optimistic, or pessimistic. Just logical.
