Unit Test

I have heard countless stories of how the acid base unit test is THE most difficult test of the year, and I arrived to school last Thursday fearing for my life. However... honestly, it wasn't that bad. I'd even go to say that the last unit test on aqueous solutions was a bit more difficult than this one. A good chunk of this unit test was basic vocab, essentially textbook comprehension questions. The other portion consisted of math, which were really not terrible at all. There were maybe one or two which I simply could not figure out how to do, but other than that, the rest of the test went by in a breeze. I'm really thankful that I survived that unit test, and I hope my grade will reflect my thoughts on it.

http://www.illini-nation.com/this-illini-season-really-isnt-that-bad/

Some links I used to study and will be using for the final:
http://www.chemtutor.com/acid.htm#math
https://www.khanacademy.org/science/chemistry/acid-base-equilibrium/titrations/v/titration-calculation-example

Unknown Acid Lab

This week, we've been working on another titration lab that is pretty much identical to last week's Acetic Acid lab. The only thing that's changed is that we're not using acetic acid, rather an unknown acid. We still titrated the unknown acid with NaOH, just like the acetic acid lab. Another thing that's been added to this lab is that we have to heat the solution as the unknown acid does not dissolve as easily as acetic acid. It's pretty neat seeing the solution turn into a mini tornado when the magnetic thingamajig is added to the flask and spins due to the magnet in the heater.

One frustrating thing about this lab is that we can't seem to get a good percent error like last lab where we got less than 1% error! The first trial of this lab gave us a 16% error, which is definitely not preferred, and the second trial gave us a 7% error, which is still not the best. Hopefully, tomorrow my lab partner and I can get at least less than 5% error.

Solution being stirred

Titration Lab

This week, we've been working on a new lab. The purpose of the lab is to standardize a solution of NaOH with KHP, and then, use that solution's molarity to determine the percentage of acetic acid is in vinegar. To start, we filled the buret with NaOH, and measured out some KHP on a weigh boat. We transfered the KHP to a flask, and filled it with water to make a solution of 75 mL. Next, we added three drops of phenolphthalein to act as a color indicator for the endpoint. Lastly, we slowly drained the NaOH solution into the flask until the solution reached a permanent pink color. This was the hard part as we never knew exactly when to stop, but then again, we couldn't go too slowly as we needed to finish within a class period. Although, I thought I sometimes went too overboard with the NaOH, we ended up getting a 0.85% error! All in all, I enjoyed this lab and watching the clear liquid turn into a bright pink in a matter of drops.

The buret filled with NaOH

KPH

KHP solution ready to be titrated

The solution turns pink where the base hits it, but then soon disappears

The endpoint has been reached!

Acids & Bases Weekly Quiz

Today's quiz proved to be quite a relief. All throughout the day, I had been stressing over this quiz as I had not done so well on the last unit test. Thankfully, when it came down to actually taking it, it was pretty much half as hard as I thought it would be. I had no trouble answering any of the questions, and I had time to double (and for some, triple) check my answers. These are the kinds of quizzes I thank the chemistry gods for blessing upon me. I have a good feeling about this one.

https://memecrunch.com/meme/DEZ5/phew

Hopefully, the rest of the unit won't get much harder than what we've learned so far, but I'm probably jinxing myself. 

Here are some of the links I used to study with which may come in handy for the unit test:

https://www.youtube.com/watch?v=Xeuyc55LqiY

https://www.youtube.com/watch?v=l5fk7HPmo5g

http://www.chemteam.info/AcidBase/AcidBase-Problems&Video.html

First Lessons on Acid-Base

We started our new unit on acids & bases on Wednesday. So far, the majority of the lessons are not very complex nor difficult to understand. I may just need to study some of the vocab again. Wednesday's lecture consisted of identifying the differences between acids and bases, strong vs. weak, and Arrhenius vs Bronsted-Lowry acids. This was probably the most difficult out of the two lectures we've had so far as it was very vocab-packed, and there are some rules that need to be memorized in order to identify what type of acid or base a substance is. Today's lecture was more math based in that we had. It was basic math and involved a simple formula to find the M of either H or OH ions in a reaction. Overall, these two lessons have not been difficult, and I am hoping that the rest of the unit will not be super bad (but it probably will).

A good summary of what we learned:
http://www.chem.wisc.edu/deptfiles/genchem/sstutorial/Text12/Tx121/tx121.html

Vitamin C Lab

On Monday and Tuesday, we performed the Vitamin C lab. My pre lab question was a math one, and it really wasn't hard at all. You just needed to know the formula of calculating concentration by dividing the drops of iodine needed to reach the endpoint of the sample over the drops of iodine needed to reach the endpoint of the standard. The actual lab consisted of measuring the number of drops of iodine were needed to reach the endpoint (when the solution turned permanently blue) of various fruit juices: pear, apple, grapefruit, v8. We then compared these numbers to the number of drops needed to reach the endpoint of a standard Vitamin C solution, made by a dissolved 500mg Vitamin C tablet in 500mL of water. We performed 3 trials while everyone else mostly performed 2 trials. This was to make sure we were being extra accurate, but when we actually looked back at our data for the trials, it seemed as if that extra trial just threw the average off. For example, the standard solution had endpoints of 39, then 27, and finally in the 3rd trial, it had an endpoint of 55. So, it totally threw off the average of the endpoint of the solution. This was probably due to the fact that we did the third trial on the second day of lab, when we had a new standard made. The standard was most likely much different than the standard from day one, throwing our number off.

Making the standard: mini tornado!

Clear solution of  juice

Some iodine has been added and the solution turns blue for a second
before disappearing back to clear

Endpoint has been reached!

Finally, we compared the numbers to figure out which juice had the highest concentration. The more drops of endpoint, the higher the concentration that solution would have. The lineup from most concentrated to least was Vitamin C standard, apple juice, v8 Golden Goodness, and finally, pear nectar.

Overall, this lab was pretty interesting to watch the color of solutions change. It did grow tedious for the solutions (Vitamin C standard) that took a large number of drops for it to turn blue. I enjoyed this lab and look forward to the future labs of this unit.