Correction to VSEPR Lab

The correction to the 2nd VSEPR lab has been made and is posted in the same place on the Events calendar as the original. The last slide was changed from sulfur monofluorine tetrahydride (SFH4) to iodine monofluorine tetrahydride (IFH4). Also, if the file for the Power Point becomes too large to send via email, please bring the file to me on a CD or a Flash drive. Please come and see me if you have any questions about the lab.

The question #5 from the Chapter 8 WebAssign has been removed due to difficulties completing the problem.

On Wednesday, you will be receiving an optional review assignment for the unit exam which will be this upcoming Friday, November 19th. I will try and have a podcast of the solutions posted so you can assess your comprehension of the material on the unit.

VSEPR Lab

You were given the VSEPR lab today in class. The lab will be due next Thursday, November 18th, 2010. The lab that you need to access is posted on the Events Calendar on the AP Chemistry web-site. VSEPR is an acronym for Valence Shell Electron Pair Repulsion. It is the repulsion of the electrons that create the geometric angles between the bonding and non-bonding ligands. Remember, non-bonding ligands repel more than bonding ligands. That is why the bond angles decrease as bonding ligands become non-bonding ligands within a particular type of parent geometry. Remember on the parent geometry trigonal bypyramidal, the equatorial bonding ligands transform to non-bonding ligands first because of the greater bond angles (120^o vs 90^0) allows for more space between the non-bonding ligands. (Non-bonding ligands repel more than bonding ligands.)

Molecular polarity - is a molecule symmetrical (same charge distribution all around the molecule) or asymmetrical (charge distribution is unequal around the molecule)? Symmetrical is a non-polar molecule and asymmetrical is polar. When you build your molecules, any difference in color for pipe cleaners used will cause the molecule to be asymmetrical, thus polar.

Please see me if you have any questions concerning the lab or concepts needed for the lab.

Take-Home-Quiz and Hybridization Recap

Below are two images of Power Point slides that have the questions that need to be answered for tomorrow, Friday, November 12th, 2010. Please have your solutions / answers to the problems ready to turn in at the beginning of class.

I would like to go through a quick recap of hybridization for bonding.

• A single bond always involves only a sigma bond. A sigma bond is between two hybridized orbitals or a hybridized orbital with a non-hybridized 1s orbital of a hydrogen atom.
• A double bond always involves a sigma bond and pi bond. The pi bond originates from two non-hybridized p orbitals overlapping.
• A triple bond always involves a sigma bond and two pi bonds.
• Ligands are either covalent bonds or non-bonding electron pairs. A single covalent bond, double covalent bond, or triple covalent bond are all considered one ligand.
• sp^3 hybridization is required when four ligands surround an atom. The hybridized orbitals can be used for sigma bonds or to hold non-bonding electron pairs.
• sp^2 hybridization is required when three ligands surround an atom. The hybridized orbitals can be used for sigma bonds or to hold non-bonding electron pairs.
• sp hybridization is required when two ligands surround an atom. The hybridized orbitals can be used for sigma bonds or to hold non-bonding electron pairs.

General Information

The WebAssign is up for chapter 8.

Do it for the band!

For those of you that were in class today and those of you that were not, this post has something for all of you. First, a VodCast showing the solution to the problem given in class on Thursday, October 21st has a link and file on today's date on the AP Chemistry calendar. You are asked to view the solution to problem #2 from the 2007 AP Chemistry Test Form B. To offer up extra incentive to view the Vodcast, there will be a quiz given the last 20 minutes of class on Monday, October 25th over the material covered on the 1999 and 2007 test. The topics covered will be the Bohr model of the atom and calculations associated with the Bohr model. The topic of bond energy will also be incorperated. To give those of you a little prize for reading the blog, any student that writes "YABBA-DABBA-DOO" across the top of his or her quiz will get extra credit on the quiz.

Also on the calendar is a link and file for the Power Point for Chapter 6 if you would like to download it. I would suggest that everyone read sections 4 through 8 of Chapter 6. Hopefully everyone has some recall of electron configurations from the 1st year course.

Finally, I want everyone on Saturday to celebrate the greatest of little known holidays. On Saturday, October (10th month of the year) 23rd, from 6.02 a.m. to 6.02 p.m., please join me in celebrating MOLE DAY!! We will have a belated celebration on Monday. I will bring treats to class. Have a good weekend.

Gravimetric-Titration Lab

So you can solve for a percent error / difference on your lab, the concentration of barium hydroxide was 0.0723 M. Also, in case you forgot to write down the molarity of the sulfuric acid solution, the concentration was 0.119 M. Your lab reports will be due on Tuesday, October 19th, 2010. Remember, on Monday, October 18th, you will be having a quiz over the analysis and calculations associated with the lab.

Calorimetry Solution and Two More Problems

Below are the two problems (Calorimetry #1 and #2) that I would liked solved before class tomorrow, Thursday, October 7th, 2010. Below the two problems is the calorimetry problem presented in class and the solution to that problem.