Oxidation Numbers

The rules for determining oxidation numbers are:

• Each atom in a pure element has an oxidation number of zero.
• For monatomic (metal cations) ions, the oxidation number is equal to the charge on the ion.
• Fluorine always has an oxidation number of -1 in compounds with all other elements.
• Cl, Br, and I always have an oxidation number of -1 in compounds, except when combined with oxygen or fluorine.
• The oxidation number of H is +1 except in compounds with metals (hydrides) when H is -1
• The oxidation number of O is -2 except in peroxides when O is -1
• The algebraic sum of the oxidation number for the atoms in a neutral compound must be zero. In a polyatomic ion, the sum must be equal the ion charge.

Remember:

• Oxidation numbers can be fractions
• Oxidation numbers and charges are not the same thing, nor are they written the same
• +2 is oxidation 
• 2+ is charge

Oxidation Number Practice Quiz
More information

Chemistry Lab

Last week we did a lab that involved mixing different chemicals together and observing any reactions taking place. Overall, it was a simple lab, but it was cool to see the different reactions happening. After our data was collected, we found the molecular and complete ionic formulas of each of the successful reactions. Below are pictures of all of the reactions. As you can see, some combinations of chemicals had no change, some caused a slight color change, and some caused a drastic color change.

Molecular vs Empirical Formulas

During this unit, we learned to differentiate between molecular and empirical formulas. We learned that empirical formulas are the lowest whole number ratio of elements in a compound while molecular formulas are the whole number multiple of the empirical formula. Remember the empirical and molecular formulas of a compound can be the same. Here are some websites that go more in depth.

Molecular vs. Empirical Formulas

How to find Molecular Formula

How to Find Empirical Formula

Practice Quiz

Finally Made it into Lab!

So today, my partner and I both passed the pre-lab quiz for the first time all year. This means we got to complete our first lab! As for our class overall, there were four total lab partnerships that passed. That is quadruple our original record. The lab was about figuring how to find the formula of a chloride. We did this by measuring the mass of the empty beaker, the beaker with the piece of zinc, and the beaker with the zinc chloride compound. The first picture shows the piece of zinc in the HCl in the early stages of heating, so the zinc has not dissolved much yet. The second picture shows the end product after heating the zinc and HCl. The third picture shows my calculations to how I determined the formula of the chloride.

Well That Was Rough...

Yesterday we took our first quiz for this unit, and it was rough. During the quiz, I could tell that I was forgetting to look for a lot of things, such as the diatomics, so I was not expecting to get a good score.  Quiz grades were entered in the gradebook this morning and I was not surprised. On the brightside, it was only 17 questions, so it did not completely cause my grade to plummet, but that means that with few questions, each missed question dramatically affected the quiz score. Hopefully the unit test next week will go better, I just need to review. Below are some helpful links.

The Seven Diatomics

Different Diatomic Acronyms

Solving Problems Using Moles

Yesterday in class we learned how to solve problems using moles as a unit of measurement. Basically, this lesson was an exapansion on dimensional analysis, a skill which we learned last unit. The picture below serves as a guidance to find the right answer when converting between grams, moles, representative particles, and/or the volume of gasses.

Pretest

Today we took the prestest for our new unit. While taking the test, I barely knew any of the material. Usually during pretests, I can gather a vague idea of what is going on, but this time I could not figure out almost anything. My score of a 31% reflects these thoughts of unfamiliarity with this unit's content. It looks like the unit is a lot of calculating numbers, which is fairly easy, so I hope this unit is not that hard.

Last Meal Project

While completing my Last Meal Project, I referred to the charts below to help me. After converting the imperial unit to the metric measurement, I used dimensional analysis as explained a few posts back.

Last Meal Project Party

On Friday, we finished our week off with everyone bringing in one of their recipes from the Last Meal Project we had completed. It was nice to have an hour to relax and eat the food everyone brought in to share. The only downside was the majority of people brought in desserts, so you could not taste everything without getting sick. I think I only got to eat maybe a third of the projects brought in. Out of the ones I had the opportunity to try, they were very good, and I assume the rest were tasty too. I feel like the dishes that stood out the most were the ones that were not desserts. For example, I tried some pasta salad, sushi, and a couple different dips that I enjoyed very much. I am not saying that any of the desserts did not stand out, however. One of the desserts brought in were doughnuts that looked like monsters. They even had the plastic fangs in the middle! Also, the Reese's cupcakes with a peanut butter cup in the center and the Ande's Mint cupcakes were among my favorite desserts. It was nice to see all of the effort my fellow classmates put into their projects. The picture below shows two of the cupcake dishes brought in.

Test Grade Anticipation

On Thursday we took our unit test and I feel like I did somewhat well. A lot of the test was over the last section we learned, so it was still fresh in my mind. It was mostly just calculating numbers which I find easy. The most difficult part was remembering to round the answer to the correct number of significant figures, but the test was multiple choice, so I feel like I caught any mistakes I made while calculating. I was hoping the grade would be in now, but they are unfortunately not. This weekend was a busy weekend, so I expect them to be in this week because it should not be as hectic. I feel like I got a decent grade, but I guess we will have to wait and see.