Thoughst on Unit Test

Overall I didn't think this test was especially hard; but, like this quiz, was time consuming. It was only twelve question long but took me about 45-50 minutes to complete. Many of the question involved multiple equation inside the problem, like for finding the percent yield of a certain element given the formula, which takes about three equations to find out. Fingers crossed that I did well, which I feel like I did.

Here is a couple of was to study I found:

General Info
Sample Problems
Soft Schools Quiz

Last Lab and Percent Yield

Last Thursday we started on a three day lab that involved a reaction between iron and copper (II) chloride. On Friday we took the iron (a nail) out of the solution and some pretty cool but kinda nasty stuff had happened. Some copper was left in the bottom of the jar while iron off of the nail had dissolved into the liquid. The jar was then dumped of solution, rinsed, and left to dry. On Monday when we came back, we measured out the amount of copper in the jar. Using these measurements (weight of nail before and after reaction, weight of copper, and weight of jar) I was able to find the percent yield of the reaction was around 75%. The percent yield is the actual amount divided by the theoretical amount. This shows us how there was other stuff going on inside the reaction that we have no control of. More info on percent yield here.

          

First Day of the Lab

          

Last day of the Lab

Limiting Reagent

The second lecture my class had on stoichiometry was to find which reactant in a compound was the limiting reagent. In layman's terms, the limiting reagent is the compound that is totally used up in a chemical reaction, all other compounds are the excess reactants.

I find that this picture really helps explain exactly what is going on. Basically it shows that no matter how many tires there are, if their are only eight car bodies, only 8 cars can be made. The 16 extra tires is the excess reactant. This website shows the math and what is going on and links to a few practice problems.

Stoichiometry

Stoichiometry is a section of chemistry that involves using relationships between reactants and/or products in a chemical reaction to determine desired quantitative data. Basically this means math. It can be easily visually in a flow chart, where the compound is placed into moles, converted, and the converted compound is changed back into mass, volume, or number or partials. In class we only did conversion involving mass. The result of the conversion told us how much of amount of a species can be used to create a product in a chemical reaction.


Confused? Here is a Crash Course video that can help.

Metals Lab

Today we did a lab that involved taking six different metals and pouring chemicals on them to see of they react with each other, and it was pretty cool. Some of the metals started to bubble and smoke when they came into contact with each of the chemicals, and others dissolved into a puddle of goop. On of the metals that we used was calcium which turns out to be pretty reactive, and lead was not at all. Sadly I forgot to take a picture of the reactions at work but here what the one of calcium and water together looked like: