Chemical Composition Test Reflection

After taking the unit test today, I believe it is safe to say that I am smiling on the outside, but feeling pain on the inside. I studied a lot for this test, and even then, I don't think it was enough to prepare me for today. The majority of the questions were moderately easy, but I didn't get a chance to double-check them, so I pray to the chemistry gods that they were correct. The rest of the test, I was either confused on the wording, completely blanked on how to solve them, or simply didn't know how to do them. I guessed on roughly five of the questions which isn't too bad, I guess. We'll see though...

https://raymcdonald.wordpress.com/2011/11/09/caste-your-anxious-moments-on-jesus/

Throughout this unit, the majority of the concepts were not difficult at all, I guess just applying those concepts on the test was what made it so difficult. I am definitely going to need to review this chapter for the final exam. This is probably the first chemistry exam/quiz that I have not felt fairly confident in my answers. I'm really hoping that I did decent on it.

Formula of a Chloride Lab

I think with all this practice, these empirical formulas are becoming easier and easier to solve. Today's pre-lab quiz was really simple, and I was stoked that we were able to confer with our partners. It allowed me to catch some simple calculation errors that would've maybe given be the incorrect answer. However, I think the concept of finding empirical formulas is very simple. I just need to practice and memorize some more. The lab we did today was similar to Monday's lab, except this time, we heated zinc and hydrochloric acid. After a couple minutes on the hot plate, the zinc would dissolve into the acid, as shown in this picture.

The resulting product was a solid resembling table salt. 

Like the Formula of a Hydrate lab, we took the masses of the beaker, beaker plus zinc, and beaker plus zinc/acid. These masses would be used at the end to calculate the empirical formula of zinc chloride.

Overall, this lab was interesting. The only thing I absolutely despised was the SMELL of the chlorine gas. It smelled kind of like metal, but VERY pungent metal. Looking forward to future labs.

Empirical Formulas

Today's lesson was pretty simple, but chockful of tedious types of problems. We finally learned what empirical formulas are, as many empirical problems were on the pretest which I did not understand at all. However, after the lesson today, I am now aware that they are really simple. Empirical formulas are simply the lowest whole number ratio of the elements in a compound. For example, H2O is an empirical formula as the numbers of elements cannot be reduced any further. On the other hand, N2O4 is not an empirical, rather a molecular formula because it can be reduced. When it is reduced to NO2, it becomes an empirical formula. So, pretty straightforward. We also learned how to find the empirical formula of a compound using a given mass or percent of an element in that compound. 

Here are some empirical formulas practice websites: Chemistry.about and SoftSchools

Bozeman Science also has a video that contains some empirical formula lessons.

I am looking forward to our lab tomorrow. Hopefully, I will be able to look over the lab and my notes tomorrow and a bit tonight as I have not had much time due to having to stay at school until after 8 p.m for the fall play tech week. BTW,  everyone should come to the play!! Opening night is tomorrow at 7 p.m, and tickets are 5$. I'd love to see some of my chem pals support drama club!

Formula of a Hydrate Lab

On Monday, we had our pre-lab quiz for the copper sulfate hyrdate lab. To my relief, my partner and I both passed! I had been stressing over it for the entire day, so I was very glad to have passed. We first took the mass of the test tube and then the mass of the test tube and the copper sulfate. Next, we used the bunsen burner to heat the substance until it turned white, indicating that it had changed into an anhydrous salt. Apparently, we were supposed to take the exact number that was shown on the scale, but instead, we rounded the mass numbers to the nearest thousandths as that was what was on the lab paper. This led to a large percentage of error when we calculated for "n" of the hydrate based on our mass numbers. It was actually 14%! We went back and tried to recall the exact numbers that were on the scale. We also had to reweigh some of the items to get the accurate mass reading. When we re-calculated for "n" with our more accurate mass numbers, we still got about 14% error. Our last option was to heat the substance some more, making it much more whiter. This led to a decrease in the mass of the test tube plus the anhydrous salt. With THIS new mass number, "n" was much closer to the needed value of 5, giving us only a 1% error!

Final thoughts on the lab: I believed it was a pretty interesting lab; It was super cool to watch the blue gradually turn into white as the water evaporated. Hopefully, next time we will remember to use the whole mass reading on the scales to prevent errors.

Hydrates and Anhydrous Salts

On Friday, we learned about hydrates and anhydrous salts and how to solve conversion problems with them. I believe that these past couple conversion lessons are pretty easy with a lot of practice. It is however difficult to remember all of these rules and formulas for various types of problems, but I just need some more practice. The big picture idea for this lesson is that hydrates are substances that contain water molecules, and anhydrous salts are substances that previously contained water molecules. When water is removed from the hydrate, the anhydrous salt is what is left over. ChemTeam  contains some good practice problems for figuring out the formula for a hydrate.

http://fphoto.photoshelter.com/gallery/Compounds/G0000P8DRfn82fkA/C0000AGiG6IN5fGI

We have a pre-lab quiz coming up on Monday which I am extremely anxious about. I have been studying quite a bit, but I am worried that a question will completely throw me off, and I won't be able to participate like during the Aspirin Lab. I will be practicing those hydrate problems to become more efficient at doing them in order to use my time wisely during the pre-lab quiz. The lab looks very interesting, and I very much hope I will be able to participate. Fingers crossed.

First Lessons on the Mole

Today and Wednesday were lecture days. After being so confused while taking the pre-test, I was surprised to learn how fairly simple these first couple concepts are. It is mainly converting moles into various units and vice versa for both elements and compounds. Doing more practice will definitely make me more efficient at doing these sorts of problems. This site, Chemistry.wustl.edu, looks very helpful. I believe I have stated before that one of my favorite chemistry videos to watch are Bozeman videos; this one corresponds to the Mole lesson. Another video of his that is very detailed and easy to follow is this one explaining mole conversions.

http://t-shirtguru.com/2013/01/31/mole-problems-t-shirt-mentalfloss/

At first, I was a bit confused since I thought that moles and molecules were the same things, but in reality, moles are just a unit of measuring particle amount. Moles can either be of atoms of an element or molecules of a compound. Additionally, it will be crucial to memorize those polyatomic ions and nomenclature rules. I will definitely be reviewing those as making a naming mistake leads to wrong answers.

Chemical Composition Pre-Test

Today we took our unit pretest on chemical composition. The test contained questions regarding density and molecules. I was uber confused on the questions asking how many molecules in a specific mass or volume. Some questions I tried and re-tried calculating, but it didn't work, so I just guessed. This unit seems to be one of the harder units. I hope those confusing concepts will be made clear after the lectures. One concept I had not ever heard of were empirical formulas.

http://jencrazyscience.blogspot.com/2012/09/chemical-composition-of-earth.html

I am very curious as to what and how to calculate problems according to molecular mass. I also need to review the poly-atomic ions. Additionally, I am also very interested as to what the project/lab will be for this unit.