Experiment 11: Unknown Analysis

This day has been awesome. No, in fact, this whole week had been a blast. Despite all my awkwardness and everything, I can say that I enjoyed these past few days because, well, it was amazing. I would surely like to rattle off about how this week went, but due to time constraints, I'll just be sharing about one relevant thing that transpired today - the unknown analysis.

I have a Chem 16 class every Wednesdays and Fridays at 7 AM. Last night I went home by 10 PM from the tambayan. I tried to finalize the assignment for chemistry and to be more productive, but I was so tired my eyes wouldn't stay open. I had no choice but to sleep. I awoke by half-past one (which was an hour late from the time I set in the alarm), did the assignment, prepared for the experiment, and slept at 4 AM. I set the alarm to 5:30 AM, but I was stunned when I awoke (after turning off the snooze numerous times), that it was already 6:30 AM, for goodness's sake. It was the first time that I had woken up that late. Good thing, I was able to leave the dormitory by 5 minutes to 7 AM. Our professor was a bit late, so I was safe. However, I was beginning to be very frantic by then. Today is Unknown Analysis day, and although I had prepared by scanning the manual and so, I was still terrified. I want to love chemistry, it's super cool, so much so that I initially planned to major in materials physics. But heck, it can be very difficult, and to someone who went to college with zero knowledge in the subject, it was even worse. I know I suck in this subject; good thing I passed the first exam with satisfactory results.

Okay. The experiment was a joke. After performing the cation test, I was able to limit my choices between zinc and calcium, since precipitate formed upon addition of NaOH. Upon performing the confirmatory test, formation of precipitate occurred again so I was certain I got Zinc. For the anion test, there was no visible reaction upon the addition of barium nitrate, so sulfate, phosphate, and carbonate were ruled out. After performing another test, it all went down to SCN and nitrate. God, I didn't want to perform the brown ring experiment. My solution looked weird; I mean, I didn't really achieve the colors that SCN or nitrate was supposed to have. However, I thought the solution looked peach (which it was supposed to be if it had SCN) and the toluene layer was colorless so I assumed thiocyanate was present. I approached my professor and was about to have my first guess...

...And he told me I got both guesses wrong.

I had never felt so inadequate in my life. I tried the elimination tests again for cation, and was able to rule out Ammonium. In the end, after several trials, I went to our professor and convinced him that there was zinc in my solution.

"Sir, precipitate formed upon addition of ammonia, so it's zinc. Precipitate also formed upon adding NaOH."

He surveyed my test tube and said, "Add some excess ammonia and observe whether the precipitate will dissolve."

It did. It must mean that there really is some zinc present. Fast forward, it turned out that there was some confusion involved. He said that he never told me zinc wasn't there. I replied that he said both of my guesses were wrong, so of course zinc was. Our professor admitted the existence of zinc and I felt so cheated since I repeated everything just to be sure.

The next problem would be the anion. If it weren't SCN, it had to be nitrate. I knew this, and yet I repeated the elimination and confirmatory tests because I didn't want to perform the brown ring experiment (the 18 M sulfuric acid sounded so menacing). But I was left with no choice so I performed it using my solution which already had the toluene layer, as was advised by my classmate. I was so ecstatic that the brown ring appeared, but in the end the process was wrong and I should have used a fresh solution. Sadly, upon doing so, nothing appeared.

I lamented this to our professor and he told me to repeat the experiment. Obviously, there really was nitrate on my solution. I just had to show him some proof. I repeated everything, to no avail. He must have pitied me because he said that there was indeed nitrate, but I was still lacking one more ion. I knew what it was all of a sudden, and I realized how cunningly our professor had chosen the other ion.

"Calcium," I said. He smiled and confirmed it. I was supposed to receive 15 points, but I only got 12. I'm not complaining.