Unit Exam reflection

I was so glad that the exam was postponed to Tuesday because it gave me more time to study. I'd been studying from the weekend anyways, but the more time I get, the more confident I feel. To study for this exam, I mostly did a lot of practice problems. I used all the problems from schoology as well as from the textbook. I also used some external resources (listen in Stoichiometry summary post). I am trying my hardest on this unit exam because it is our last chance to raise grades before the final exam. I also know I need to learn this unit well because I'm sure that we will be using this for the remainder of the course. I can tell that things are only getting harder from here.

Stoichiometry Summary

I thought this unit was pretty simple in comparison to the last few units because this unit was more of an application of all the previous knowledge that we had and really the only new things we learned were the processes to solve certain problems. All the problems mostly consisted of the same basic process of starting with a balanced equation and went from converting to moles, to using the balanced equation ratio and then converting back to grams if necessary.

We can use the above process to find the mass or moles of any reactant or product in the balanced chemical equation if we are given a mass of a product or reactant to begin with. 

Example: What number of moles of O2 would be produced by the decomposition of 13 grams of water.

More practice: 

• http://www.chemistry.wustl.edu/~coursedev/Online%20tutorials/Plink/Stoichiometry/stoichset.htm
• http://science.widener.edu/svb/tutorial/genstoichiometrycsn7.html

Limiting Reagent

Limiting reagent- the reactant that is completely used up when a reaction is run to completion

To find the limiting reagent we can run both reactions to find the amount of one product and the reactant that produces the least amount of product is the limiting reagent. 

We can then use that to figure out how much product will actually be created (which will be the product created with the calculation of the limiting reagent)

Practice: 

• http://www.chemistry.wustl.edu/~coursedev/Online%20tutorials/Plink/limreag/probsetlr.htm
• helpful link that explains the concept and gives examples: http://chemwiki.ucdavis.edu/Analytical_Chemistry/Chemical_Reactions/Limiting_Reagents

Percent Yield

Theoretical yield- the maximum amount of a given product that canbe formed when the limiting reagent is comopletely consumed

Percent yield- the actual yield of a product as the percentage of the theoretical yield

Practice: 

• http://tmlimitingreagents.weebly.com/percentage-yield-and-actual-yield-practice-problems.html

Copper (II) Chloride and Iron lab

I felt pretty confident with the pre-lab quiz for this unit. Actually, when I was solving the problem I was kind of scared but that was because it was pretty easy and straightforward. It was very similar to a lot of the problems on the weekly quiz so I thought the pre-lab quiz was another great opportunity to practice for the unit exam.

 When we poured the water into the CuCl2 it kind of changed colors which was really cool. Then, when we put the iron nail into the solution, we immediately saw a color change in the nail which was cool because we could already see the reaction taking place.

When we came in for the second day of the lab, there was a dramatic change and that really helped me see the chemical reaction occurring. The process for the second day of the lab was very tedious and we had to be really careful not to pour out copper when we were trying to take the water and the hydrochloric acid out of the solution. However, I understand why it is so important to not wash away any of the copper because the final mass is what will help us determine the charge of the iron that reacted with the chloride. If we wash away too much of the copper on accident, we will get a smaller mass which will give us a different percent yield which will indicate the incorrect charge of the iron.

Weekly Quiz 12/8

I thought this quiz was deceptively simple. I felt like all the problems were really similar, which I know Mrs. Frankenberg said that the processes in this unit are all very similar and have the same basic approach but it still worried me. I think I understand this unit better because I understand the calculations we are making and why we use the certain processes and methods. The math in this unit is also a lot simpler but I can see how we're connecting all the information from all the previous units. Whenever we are told that we will be tested on any of the past units I always panic but now I see how every unit uses knowledge from previous units and we're tested on those anyways. Finally, I'm concerned for how long I took to take this quiz because it took me a good portion of the class to actually complete the quiz so I hope I will be prepared enough to finish the Unit exam in time.

Metals Lab

For this pre-lab quiz, I was confused at first because of the wording of the question because we hadn't really talked about those kinds of problems in class before. However, we already knew the answer, I just didn't realize how simple it actually was. The lab was also really cool because some of the reactions were really noticeable and had really weird reactions. Again, it was a good hands on experience for actually seeing the actual application of what we'd been learning in class. This lab was also not as long as the last two labs which is always a good thing so we didn't have to rush so I was actually able to enjoy this lab and thoroughly observe it without being rushed. After the lab, calculating the net ionic reactions was also really good practice and it definitely helped me because before I started, I had no idea what I was doing, but towards the end I was pretty confident in what I was doing.