Wednesday 2.9.11

Announcements: Instead of having 7 quizzes we'll only have 6. We took a quiz today, and we're taking another  quiz tomorrow
Homework: pg 32-34 due tomorrow, Web assigns, and text questions due before the test 2/15


Today we worked on part one of our lab. We did all of the following steps listed in the picture below. To sum it up, we basically just put copper (II) chloride in water and stirred it until  the copper (II) chloride dissolved. Then we massed the nails and recorded data. After that we put the nails in the solution. We will come back to doing the lab tomorrow.

After we finished part one of the lab, we took a quiz on limiting reactants. When we finished the quiz, we used the rest of the class time to work on our homework. (pg 32-34, mentioned in bold above)

Next Scriber: Maddy M.

2/7/11

Announcements: Study for upcoming quizzes. if you missed Friday's(2/4/11) quiz, make that up as soon as you can!

Homework: journal page 27 #2, 29, 30, & 31

Today we learned more about limiting reactants; what they are, how to find out which one is the limiting one between two reactants, and also, a little more on how to draw the reaction with the product and its excess.

A limiting factor is something that you only have a limited supply, and then have a greater amount of something(s) else, so you can only make a certain amount of the product.

To find the limiting factors, its exactly the same as Stoichiometry, you are just take it one step farther because you are searching for something different in the end. but as a review, you must convert two different reactants into one common reactant. So to start, you will sometimes or usually have one reactant in its state of mass, you then convert it into moles, followed by moles of the common reactants. Sometimes, from here you can convert to the mass, but it really depends on the following question. You then do the same thing to the second reactant, so you should have two equations in the end. Finally, you get your two usual outcomes, just like Stoich, but with those two answers you decide which one is smaller, and the reactant that you started that equation, with the smaller answer, is the limiting reactant.

Below is a picture of an example that shows this process with actual reactants.

Since 0.065 is smaller than 0.5, that makes O2 the limiting factor

Here are some more examples of limiting reactants we did in class.

For drawing out a limited reaction, you start with the equation you are given and the two reactants that you need to determined which is the limiting reactant. You draw out your given amounts of each, and then pair them up for the out come. Which ever one does not have excess, that is the limiting reactant.

This is a picture to help show a drawn out version of limiting reactants.

NEXT SCRIBER: Alyssa P

2/1/11

HAPPY TWO DAY SNOW DAY EVERYONE!

Announcements: There will be a quiz tomorrow reviewing Stoich with Density.
**Remember** If you get 100% on 5-7 quizzes, you will get extra credit points so study hard.

Homework: Finish page 23 and 24

In class we reviewed Stoich. Page 20, "Stoich 3" was our homework but it was kind of hard because it involved density. So in class we also started to learn Stoich with Density (page 23). Mr. Paek taught us how to convert using density like milliliters per grams. A good example of a tough problem that might be on the quiz is shown below (since I can't upload pictures, I just typed it up).


// = FRACTION BAR

EQUATION: C2H6O + 3O2 ---> 2CO2 + 3H2O

2. c) If the density of O2 is 0.00143 g/ml, what mass of ethanol will be needed to react with 950 ml of O2?

950 ml * .00143g of O2 // 1 ml of O2 * 1 mol of O2 // 32g of O2 * 1 mol of ethanol // 3 mol of O2 * 46g of ethanol// 1 mol of ethanol = .65g of ethanol


*** Things to remember:
1. If it says g/ml, that means you start with one of them (in ^^ that case, ML) and put the other unit (^^ Grams) on top.
2. Make sure your units always cancel out. If you have Grams on top, you have to have grams on bottom in the next one.
3. Use the equation to look at how many moles each unit will need to react with the one above or below it
4. Always write the elements name (for ex: 3 mols of >C2H6O<) after how many units it is, UNLESS you want to lose points on a quiz :)


You can refer back to previous posts for more examples on how to do normal stoich without density.