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.

Quiz Reflection

Today I finally took the weekly quiz from last week. It was not that difficult nor that time consuming as there were not too many calculation problems. The quiz consisted mostly of concept and graph reading questions. This was one of the few quizzes/tests in which I actually had time to spare upon completing it.

http://www.gmlcpa.com/its-a-wrap-tax-season-2014/

Although the calculation portion of the quiz was pretty straightforward and not complicated, I suspect that the calculation problems on the test tomorrow will be a bit more detailed and complex. This means more practice for me :)

Some helpful links for studying:

http://www.nclark.net/MolarityPractice.pdf

https://www.youtube.com/watch?v=SXf9rDnVFao

https://chemistry11mrstandring.wikispaces.com/Stoichiometry+Calculations+Involving+Molar+Concentration

https://www.youtube.com/watch?v=KVZ_KS45rVg

http://chemcollective.org/activities/tutorials/stoich/solution_stoi

http://www.brainstretch.net/introChem/molesToMolarity/molarity/molarity.htm

Murder Lab Investigation, Day Two

Day Two consisted of weighing the dry filter paper that contained the solid from the reaction. The solid was a pea green powder.

After weighing the filter paper, we subtracted this mass from the mass of just the filter paper to figure out the mass of the solid. Then, we calculated the molarity of this substance and found out that it was roughly 0.07 M. To figure out the identity of the unknown substance, we knew that it must have been silver nitrate because when silver nitrate combines with sodium carbonate, it should make a solid, which is exactly what happened in lab. The 0.07 molarity matched Mr. Green's description, as he was found with traces of silver nitrate with a molarity between 0.05 and 0.15 M.

Murder Lab Investigation, Day One

The murder investigation lab seemed to be a very interesting lab. I love the idea of solving a a mystery while incorporating chemistry into it. It gives a taste of what forensic investigators do in reality. Today's task was combining an unknown solution with sodium carbonate in a beaker. Both reactants were clear, but when combined, the product was a milky white substance.

Then, we poured this substance into a funnel with filter paper inside an empty Erlenmeyer flask to collect any solid. While letting the liquid drip down into the flask, I noticed there was a sand-like substance forming inside the liquid, showing that the reaction definitely produced a solid. Thus, it can be inferred that the unknown substance is silver nitrate, due to the fact that it should produce a solid when reacted with sodium carbonate based on solubility rules.

Molarity

Unfortunately, these past few days in chemistry have been a bit of a whirlwind as I was absent from class Thursday and Friday for a field trip, which by the way I had a great time on! However, it was frustrating to be in utter confusion regarding what we learned in class. Today, I received some notes from my peers and learned molarity on my own and within a small group. It is not that complicated, and many molarity problems can be solved using commen sense, rather than using stoich. I still need to learn about dilutions and look over the aqueous solutions packet from last week.