Solutions to Day 3 and Day 4 of the AP Chemistry Test Review

• Please go the the Events Calendar. Under the date of Saturday, April 30th, 2011 are the solutions to the problems with $ signs for the day 3 and day 4 review for the AP Chemistry test review. I hope to have the Podcast solutions for remaining three problems that were optional to do from the day 4 and day 5 reviews posted under the date Sunday, May 1st, 2011 by tomorrow morning. Make sure that you are proficient at all of the types of problems reviewed last week, but especially equilibrium problems.
• As you review for the test, make sure that you review all of the problems from last week and all of the problems from the Friday morning review sessions. At the review session held at school this morning, I noticed a lot of people using review books for the AP Chemistry exam. That is great, but make sure that you use the old free response problems as study material also. The review books usually do not match the complexity of the old free response questions.
• On Monday morning, be at school by 7:30 a.m. Be at the auxiliary gym by 7:45 a.m. If you need to borrow a calculator or you think that you need batteries for your calculator, come by room #327 prior to the exam.
• The format of the test is first the multiple choice section then the free response section. You will have 90 minutes to answer 75 multiple choice questions. You will only be given a periodic table for the multiple choice exam. You will need to remember basic equations and do simple calculations without the aid of a calculator. You will have a list of equations and constants for the free response section of the test. You will have two parts to the free response section. Part (A) is the part of the free response test that calculators are allowed. You will have 55 minutes for part (A). Part (B) does not allow calculators and is when you answer conceptual questions. You will have 40 minutes to finish part (B). The multiple choice part of the test is worth 50% of your overall grade and the free response is the other 50%.
• Remember, you are not only studying for the AP Chemistry exam, but also for the final for the AP Chemistry class, which will count for 20% of your semester grade. The test will given over a total of three days. On Tuesday, May 3rd, you will take the multiple choice section of the final. On the AP multiple choice test, you get roughly 50 seconds per question. The multiple choice test for the final will be designed with 41 multiple choice questions to be completed in a 50 minute time frame. Wednesday, May 4th is a late start day, so no part of the test will be given. We will choose the class T-shirt that day. On Thursday, May 5th, the non-calculator portion of the free response part of the exam will be given. Time limitations of the real AP Chemistry test will be followed, so you will have 40 minutes that day to complete the exam. On Friday, May 6th, the calculator portion of the free response part of the exam will be given. You normally have 55 minutes for this part of the exam, but will only be given 50 minutes. I will remove parts of the original questions to make it fair terms of time. On Monday, May 9th, I am going to reserve that day for any make-up exams that need to be completed. If you have completed all exams, you will be released from class. Remember, I will curve the final and then add the extra credit that you have earned by coming to the early morning sessions and the practice exams. After studying for the real AP Chemistry exam, you should not need to day any more studying for the class final. I will make sure to choose questions that address material that we have covered extensively in class and during the review process.
• For the class final, you will have an equilibrium problem for the first part of the calculator portion of the free response section. Since we did not have a test over thermodynamics (entropy, enthalpy, Gibb's free energy) and electrochemistry, I will guarantee you questions on the free response part of the final exam covering those topics. I will also guarantee you a question covering chemical reactions like the once given on the day 3 review from the last week of class.
• Feel free to call me on my cell phone if you have any questions tomorrow as you study. You should all have my number. If not, call someone in class that may have it.

Day 4 In Class Problems Corrections and Clarifications

Below are partial solutions to the problems done in class.

• For the last question done in class,1998 #1 b) i), there was an error. We (I) forgot to square the value for the hydroxide concentration, thus the value for the zinc ion concentration was wrong. The correction is in the solution below. I caught the mistake with a student when we did the confirmation of "Q" when we plugged in the concentration values, so the lesson is always confirm your answers if you have the time.
• For part (d), 1996, there was some confusion. In the solution below, I showed how you could use Henderson-Hasselbalch to solve for the concentration of the conjugate base. Since both the pH and pKa are the same, subtracting pKa from pH would leave you with zero. To solve for "x", the inverse of log has to be performed. This would make the zero on one side of the equation "1" and possible to solve for.
• Part (d), 1996 can also be solved by knowing the concept that pH is equal to pKa when you are at the half-way point of a titration. That is when the amount of conjugate base is equal to the original acid. This ratio would be one. The log of 1 is zero, thus pH is equal to pKa. The problem gave the concentration and volume of the acid, so the millimoles of the acid at the equivalence point can be determined. For the problem, 10.0 millimoles of acid would be at the equivalence point. Therefore, half of 10.0 millimoles is 5.0 millimoles, which is the amount of NaOH that would be added to get the ratio of acid to conjugate base just right to have the desired pH.

The solutions for the day 3 problems will be on the Events Calendar tomorrow morning. Remember to finish the two problems on the day 4 packet for tomorrow that have $ signs by them. There are two extra problems, but those are optional to do. I probably will not have the Podcasts done for the two extra problems until Saturday. The last early morning review session is tomorrow at 6:30 am. We will be doing two problems during the session.

Solutions 2005 #8, 2005 (Form B) #2, and Molar Mass Determination

On the Events Calendar under today's date, Tuesday, April 26th, 2011 are Podcast solutions to the final two Electrochemstry Packet problems, 2005 Free-Response #8 and 2005 Free-Response (Form B) #2. I have also made a Podcast on how to solve for molar mass using a variety of different methods. This is meant to be a review for the AP Chemistry test and final test. There is no homework associated with this Podcast.

Solution to All of 2005 #2 and Part (d) of 2004 #2

Below are the solutions to problem 2005 Free-Response Form A #2 and part (d) of 2004 Free-Response Form B #2. I really botched part (d) today in class, so I wanted to make sure that everyone saw the simplest and correct way to solve the problem. I am pleading temporary insanity for making the problem way harder than it had to be. Please finish 2006 Free-Response Form a #3 and 1993 Free-Response #2 for tomorrow. They will be checked for credit. Also have the Electrochemistry Packet complete and ready to turn in tomorrow for credit.

Electrochem Solutions 2001 #7; 1996 #7, and 1998 #8

On the Events Calendar on the date Saturday, 4/23/2011 are three solution Podcasts for problems in the Electrochemistry Work Packet. Two of the solutions, 2001 #7 and 1996 #7, are assigned homework problems. The third solution, 1998 #8 was done in class. I did a Podcast for the 1998 #8 problem because we went through the problem rather quick in class. I wanted to give you more time to look at the problem because there are multiple ways to answer parts of the problem. I addressed all potential ways of answering the questions within the Podcast. The rest of the problems in the Electrochemistry work packet are due on Tuesday, April 26th, 2011. You are required to do all of the problems outside of class that have a $ sign next to them.

Balancing Redox Reactions Quiz and Announcements

The quiz to completed for tomorrow, Tuesday, April 19th, 2011 is below. This is review from last fall and notes on how to balance a complex redox reaction were part of the notes package given out today in class. Please remember this week is another opportunity to take a practice AP Chemistry Exam. The test will be from 1999 and the opportunities to take it are Thursday night (4/21) from 7:00 pm to 9:00 pm OR Friday after school (4/22) from 2:30 pm to 4:30 pm OR Saturday morning (9:00 am to 11:00 am). Also, the solutions to the final two problems (1992 #3 and 2009 (B) #5) from the Chapter 19 work packet have been posted on the Events Calendar under today's date (Monday, April 18). I will be collecting the packet tomorrow to check for completion of work.

2004 (Form A and B) Free-Response Questions #2 and #7 Solutions

The solutions to the 2004 Free-Response Questions (#'s 2 and 7) from the Chapter 19 work packet are posted on the Events Calendar under the date Friday, April 15th, 2011. The homework for the weekend is 1992 Free-Response #3 and 2009 Free-Response Form B #5.

1999 Free-Response Question #6 Solution

Go to Events Calendar to view the PodCast for the solution to the 1999 Free-Response problem #6. It is posted under the date, Thursday, April 14th, 2011. Tomorrow morning (Friday, April 15th) at 6:30 a.m. is another review session for the AP Chemistry exam. Also, for homework tonight from the Chapter 19 work packet, complete problems 2004 Free-Response #2 and 2004 Free-Response (Form B) #7.

Solutions to WebAssign Problems and Some Reminders.

Remember, tomorrow your Chapter 17 Take-Home-Test is due. There is a reason that I showed you the presentation on Kidney Stones on Friday. That is to convey to you the idea that acids increase the solubility of non-soluble (or low Ksp) solids. Keep this in mind for a question on the exam. Also, the Chapter 17 WebAssign is due tomorrow. On the Events Calendar are two solutions to problems on WebAssign. One is for the pH determination during a strong acid / strong base titration. This is posted under the date, Saturday, April 10th and is for WebAssign #8. The second solution is for the pH at the equivalence point of a weak acid / strong base titration. This is for #10 on WebAssign. The Ksp for calcium hydroxide lab is also due tomorrow.

Completed Solution - #3 Ksp Packet

Below is the finished solution to #3 from the Ksp packet. We started #3 in class, but ran out of time. The "Q" was larger than the Ksp value given, so a precipitate will form when the two solutions are placed together. Because a precipitate will form, the B.C.E. table will be used. Notice in the B.C.E. table, the two to one ratio of fluoride ion to barium ion is taken into account by dividing the 1.100 moles of fluoride ion (the limiting reactant) by two. This is also repeated for the formation of the precipitate barium fluoride. When solving for "x" in the Ksp problem, adding "x" to the barium initial concentration was not taken into account because the disparity between the Ksp value and initial concentration of barium ion was large. The percentage between the two was 0.4%. Notice how a confirmation was done at the end of the problem to ensure that the problem was done correctly. A podcast was made showing the solution to #4 of the Ksp packet. The solution can be found on the Events Calendar of the class website under the date April 4th.. Please finish #5 for tomorrow.

Titration / pH Determination Problem Solution

In class on Friday, April 1st, a solution to WebAssign problem #9 was started. It is a difficult problem, so I made a Podcast showing a solution to the problem. The file can be found on the class Events Calendar under the date, Sunday, May 3rd. Also, #8 from WebAssign is similiar to to #9, but not as complicated. Number 8 only deals with a strong acid and a strong base in the titration. Number 9 deals with a weak base and strong acid in the titration. Therefore; #9 involves equilibrium and the Hendereson-Hasselbalch equation. Make sure to complete the quiz on the previous post for class on Monday, May 4th. Have a good weekend.

Buffer Quiz

Below is the quiz for making a buffer that needs to be completed for Monday, April 4th. Also, look back to the blog for information about a solution to WebAssign #9. It is a pretty difficult problem, so I am going to do a podcast on the best way to do the problem. Have a good weekend.