Unit Test

On Friday, we had our unit test for this unit. I feel like I did not completely fail it, but I do not think I did extremely well. I did many practice problems to review things such as molarity, solubility curves, and mass percent to prepare for the test, but I still had issues with some of the questions. I hope I did somewhat well because I do not want to start off the semester with a really bad grade in the class.

Murder Mystery Lab

   In this lab, we used our knowledge of molarity to determine who killed Miss Scarlet and with what. We were told that the substance that killed her was either silver nitrate or potassium iodide. We were also given a list of suspects that all had one of those two solutions in their possession, but with different molarities.We were also given sodium chloride and sodium carbonate to test with the unknown solution to determine its identity.

  Before we got into lab, we had to see which of the two options for the unknown substance (the substance used to kill Miss Scarlet) would react with which indicator, if any. For this we used our knowledge of double replacement reactions and solubility rules. The calculations for this step are shown below.

   When we tested the unknown substance with sodium chloride, the solution turned white, indicating a reaction. This meant that the unknown substance was silver nitrate. Then, we mixed 10 mL of silver nitatrate with 20 mL of .100M sodium chloride. The solution is pictured below.

   We then used filter paper (which we took the initial mass of) and filtered the solution into a separate beaker. We gave the filter paper a day to dry then took the final mass of it. We subtracted the initial mass from the final mass to find the mass of the precipitate. The calculations for this are shown below.

   We took this to find the molarity of the silver nitrate, which was .09M. This placed the murder substance in between the molarities of .05 and .15 which was listed in the suspect description of...

Helpful links that may help to understand this lab:

Solubility Rules

Double Replacement Reactions

How to Find Molarity

Weekly Quiz

We recently took our quiz over this current unit, aqueous solutions. The quiz was 24, so you could miss a couple of questions and still get a decent grade. The first two questions on the quiz were over limiting reagents which I forgot how to do. This freaked me out because I thought the rest of the quiz was going to involve them, but luckily, it did not. Today I got my quiz back and worked through those first two problems so I can do them if they appear on the test, which I assume they will. The rest of the quiz did not go horribly wrong. I did not get a fabulous grade, but I am fairly pleased with it. Hopefully I can do just as good if not better on the unit test Friday. 

Limiting Reagents Review

Limiting Reagent Review Video