Monday, April 11, 2011

Today, class begin with Mr. H putting up the answers to a reading sheet that was a due a few days ago. It was Reading Sheet 12.1 the answers are as follows:
1.
F
T
T
T
F
F
F
2. b
3.e
4.c
5.d
6.a

As Mr. H explained the contents of the reading sheet, we took down the answers. The 12.1 reading and Mr. H's class discussion provided a basic overview on equations and reactions that are at a state of equilibrium. It was brief overview and discussion that allowed us to complete the lab where we were flipping over red and gray cards in an attempt to reach equilibrium. Now that we were able to sufficiently understand why what happened in the lab we were able to construct the graph and answers the questions on the back. The next 10 min. of class were spent constructing our graphs and answering the questions on the back.

After, we moved into our packet to a discussion on calculation the Kp and Kc expressions of a chemical equation. To construct the expression for Kp you have to take the partial pressure of the products over the partial pressures of the reactants on the bottom. Also, whenever there was an aqueous solution in the equation you are supposed to replace the partial pressure with its concentration. Three basic rules or principles were all that was needed to write express the Kp for gas phase systems.
1). Products always come over reactants in the fraction.
2). Raise the partial pressures of the gases to their coefficient in the balanced chemical equation.
3). When calculation the expressions exclude any liquids or gases.

The following picture shows the answers to the practice problems we did:


Sorry it is sideways.

Remembering those three rules, Mr. H guided us through the process of calculating the Kp constant as we did some problems as a class and most of the packet page(pg. 11) individually. We then moved on to calculating the Kc constant which you needed to follow the three rules for as well. The only difference is that to the equation is the concentration of the products multiplied by each other over the concentrations of reactants. As stated before, the same rules apply.

On page 12 these are the answers to the two problems we did:

1. Kc=[NO2]^2/[N2O4]
2. Kc=[Pb2+]x[S2-]/1

Mr. H ended class by informing us about a change in the grading scale. Homework will no only be worth 5% of our grades. The 15% previously dedicated to homework will be based on small quizzes like the one we received on Friday. Two webassign assignments for homework. A reading sheet due on Thursday and a 40 QUESTION WEBASSIGN due next monday before the test. Mr. H highly advised beginning it to prevent procrastinating.