Acidic Nature of Highly Charged Metal Ions Quiz

Please complete the quiz below for tomorrow, Tuesday, March 15th, 2011. All "highly" charged (+2 or >) metal ions in an aqueous solution are acidic in nature. This is due to the metal being able to hybridize its outer orbitals (sp^3; sp^3d; sp^3d^2) and act as a Lewis Acid (electron pair acceptor). The waters are good Lewis Bases (electon pair donors) with the two non-bonding electron pairs attached to the oxygen of the water molecule. The highly charged metal ion will cause the shared electron between oxygen and hydrogen to be much closer to the oxygen, thus making the ability of a hydrogen to leave the complex ion much better.

The complex ion in the question, hexaaqua aluminum ion, would be octahedral in shape with six ligands (waters) surrounding the central aluminum ion. The hybridization of the aluminum ion would be sp^3d^2. The question asks that you write a dissociation reaction for the I.C.E table, so make sure to show Al(H2O)6^+3 losing a proton and show the resulting conjugate base.

Beginning of Chapter 16

The WebAssignment for Chapter 16 is ready to go. I would advise that you print off a copy of the assignment because I am going to use problems from WebAssign as my focus for discussion in class. The WebAssignment is quite large, so you would be wise to constantly work on the assignment so you are not overwhelmed at the end of the Chapter. We will finish Chapter 16 prior to spring break. I have also posted the Power Point for Chapter 16 on the Events Calendar of the class website under the date of March 1st, 2001. You may download it and print it off if you choose.

Chapter 15 Equilibrium Test

Tomorrow is the test over Chapter 15, Equilibrium. The test will be all written and consist of six questions. Some of the questions will have multiple parts. You will be given the list of equations and a periodic table supplied for the AP Chemistry exam. Below is a list of what you should know for the test and a key to the LeChatelier's Worksheet.

Know how to perform all calculations from the lab. This includes absorbance to concentration calculations, I.C.E. table set-up, and "k"(equilibrium) calculations using the data from the I.C.E. table.

For all I.C.E. table values, remember that simple stoichiometry must be followed. An example would be the relationship for a balanced equation shown below.
2A + B <--> 3C
A change of "C" would be three times larger than a change in "B". A change in "A" would be twice as large as the change in "B". A change of two "A" would be equivalent of a change of three "C".
Know how to use the equation for converting a k>p to a k>eq and vise versa.

Know how to predict the shift of a system at equilibrium by stressing the system. Remember, LeChatlier's Principle states that a system will try to re-establish equilibrium by partially undoing the stress caused to it. You will have to visually show this like you did on the LeChatelier's worksheet and also be able to discuss what the system must do to re-establish equilibrium.

If you are given a problem where there are no products initially, the shift must occur to the product side to create products.

If you are given a problem where both reactants and products are present initially, you must first determine the reaction quotient, Q, to determine the shift of the reaction. The shift must cause the value of "Q" to eventually equal k>eq.

A right shift would cause you to add "x" to the product side and subtract "x" from the reactant side. A left shift would cause you to subtract "x" form the product side and to add "x" to the reactant side.

You must always keep all "x" values; therefore use of the quadradic equation may be a must OR always first look for easy squares. What is meant by "easy squares" the values of both products and reactants can have their square roots found before doing the hard math of a quadradic equation. Look at the quiz from this past weekend as an example of this.

Use the hand out from today as a guide / reason for disregarding subtraction "x" once the equilibrium values have been placed in an equilibrium expression. If the k>eq value and the initial concentrations differ by a magnitude of 10^5 or more, it is permissible to disregard subtracting "x" in the equilibrium equation to solve for "x". "x" must still be used to determine equilibrium concentration / partial pressure values.

If solving for equilibrium concentrations of reactants and products, be sure to place the values back in the equilibrium expression to confirm that the concentrations equal the equilibrium value given in the problem.

Equilibrium Reaction Quiz

Please complete the quiz below and have ready to turn in on Monday morning, February 28th, 2011. Please have the worksheet on LeChatelier's Principle completed for Monday also. The test for Chapter 15 will be on Tuesday, March 1st, 2011. All WebAssign work needs to be done before the test is taken. The due date is Tuesday, March 1st, 2011 at 10:15 a.m. Most of Monday will be spent reviewing for the Chapter 15 test. Finally, your Equilibrium Lab write-up is due Monday. The test on Tuesday will contain questions and problems that pertain to the lab, so know how and why you did particular calculations.

Results of the Reaction Rate Test and the Kinetics Lab Write-Up

The results for the reaction rate test were o.k. The total point value for the test was 37 points. The average for the exam was a 25.38 / 37 - (68.59%) and the median was a 26.5 / 37 - (71.6%). I added a 2.25 point curve to everyone's raw score. The grades have already been added to Infinite Campus. Below is a breakdown of the scores.

# of scores/percentage/letter grade
3 / 98.0% / A+
2 / 89.9% / A-
2 / 87.2% / B+
1 / 81.1% / B-
5 / 79.1% / C+
2 / 76.4% / C
2 / 73.6% / C
2 / 70.9% / C-
2 / 68.2% / D+
1 / 65.5% / D
1 / 62.8% / D-
1 / 52.o% / F
1 / 35.8% / F
1 / 22.3% / F

Kinetic Lab Report
Use the lab report procedure that was given to you at the beginning of the year. The entire lab report must be typed. If you do not have it, I will give a short summary of the report format and special points that I will be looking for in this lab.

• Purpose: Why did you do the lab. What was being studied.
• Theory: Please do a good job on this for this lab. Discuss all of the concepts being studied by this lab. Points of discussion should be rate of reaction (what is it), concentration affects on rate, temperature affects on rate. Discuss collision / molecular theory when discussing concentration and temperature affects on rates. Discuss activation energy and what was done to determine it.
• DO NOT RE-WRITE THE PROCEDURE! I know what you did.
• Data Table: Re-Create the data table from the hand-out. Make sure to include units and report time in just seconds.
• Analysis: Show all regression data (including "r" squared) to support which order the reaction is and which order the reaction is not. Once the order has been determined, make sure to report the rate law constants with the correct units for each trial. Show the calculations using the modified Arrhenius equation to determine the activation energy.
• Sources of Experimental Error: Please do a good job on this. Give at least one SEE of substance that could alter your results. Please state what the SEE(s) are and HOW it / they can affect the results.
• Conclusion: State if results matched theory. Did the reaction rate alter the way that it should by changing concentration and temperature. All results of the lab should be touched upon. Also, discuss any alterations to the lab that would improve the results.

Chapter 21 and 14 Test

Tomorrow (Friday, February 11th, 2011) is the test covering nuclear chemistry (Chapter 21) and kinetics / reaction rates (Chapter 14). You have a total of three work packets covering all the material from the two chapters. Solutions to all three packets have been posted on the Events Calendar in the forms of PodCasts. The test will be 13 multiple choice questions (all but one from old AP Chemistry exams) and two free response questions (also from old AP Chemistry exams). You will be able to use a periodic table and equations sheet from the AP Chemistry exam and a calculator on all parts of the exam. Below are some highlights of what you should pay special attention to as you prepare for the exam.

• Make sure that you KNOW the nuclear decay products of alpha, beta, and gamma particles. Know how each would be represented.
• Be able to write a balanced nuclear decay emissions reaction. Make sure that you know how to balance the atomic numbers and atomic mass numbers of the parent and daughter isotopes.
• Know that all nuclear decay rates are first-order. A first-order integrated rate law applications can be used. Original isotope amounts, final isotope amounts, rate constants, and time (including half life time) can be solved for.
• Know how to determine rate order from concentration and time data. This is the integrated rate law which will require you to determine which mathematical relationship ([X] vs time OR ln[X] vs time OR 1/[X] vs time) gives the straightest line.
• The slope of the integrated rate law graph is the rate constant. All rate law constants are positive in value. Zero and first order integrated rate laws have a negative sign in front of the "k" value because of the negative slopes of each graph.
• Each order of reaction has its own units. Look at the packet given in class that summarizes rate law constant units.
• Know how to write an overall rate law.
• Remember, the sum of all of the orders of reactants is the overall rate order. Example: A reactant that is first order and another reactant that is second order will have an overall rate order of 3. An example for the units for the rate constant would be L^2/mol^2 x seconds.
• Know the differential method for determining orders of reactants and rate laws.
• **Be aware of the method for determining order of reactants that was presented in class with the 1997 Free Response question from work packet #2. Once one order is found, that order can be used in subsequent ratios of experiments. Thereby, cancelling concentrations of the reactant that has the known order is not necessary.
• Know how to determine the overall enthalpy (energy) of a reaction and the activation energy from a graph.
• Know that a catalyst lowers the activation energy needed to form an activated complex.
• A catalyst can be used in a reaction to form an intermediate, but is released in subsequent steps of a mechanism, therefore never consumed in the reation. A catalyst used in such a way is a homogeneous (same state of matter as reactant) catalyst. The intermediate is a substance that is later consumed in a later step of the mechanism.
• A heterogeneous catalyst (different state of matter than the reactants) usually controls the orientation of one of the reactants. This means that fewer collisions between molecules will result in the correct orientation for the reaction to occur. Fewer collisions needed for the reaction to occur results in a lower activation energy.
• For a reaction to occur, the particles must strike with: (1) sufficient energy and (2) the correct orientation.
• Know the theories behind why reaction rates change. A change in temperature changes the rate of collisions. Fewer collisions means a slower rate of reaction. More collisions means a faster rate of reaction. Temperature changes alter the value of the rate constant for a reaction.
• Changing the concentrations of reactants changes rate without changing the rate constant. A higher concentration means more collisions will happen between reactants, thus the rate of the reaction will go up. The reverse is true for a decrease in concentration. Fewer molecules, less chance of having a collision. The analogy of being in the hall at school during passing period (high probablility of bumping into someone) creating a high reaction rate OR being in the hall at school during a period (very low probability of bumping into someone) creating a low reaction rate is good when thinking about this concept.
• Be able to solve for any variable from any integrated rate law. (zero, 1st, 2nd)
• A change in concentration of a zero order reactant has NO EFFECT on the rate of reaction. A doubling of a concentration of a 1st order reaction doubles the rate of reaction, the halfing of a concentration of a 1st order reaction cuts the rate in half, etc. Doubling the concentration of a second order reactant will quadruple the reaction rate. Halfing the concentration of a second order reactant will cut the rate by 1/4th.
• The sum of all of the reactants and products of all of the steps of a mechanism must equal the balanced equation. Intermediates and catalysts must cancel out.
• The rate determining step of a mechanism is the slow step in a mechanism. The rate determining step must contain all or parts of the reactants that are part of the rate law.
• Reactants in a fast step can be part of the rate law if they are DIRECTLY responsible for making an intermediate that is consumed in a rate determining (slow) step of a mechanism.
• Know the concept of how the Arrhenius equation can be used to determine the activation energy of a reaction.

Remember, tomorrow morning (Friday, February 11th, 2011) is a review day for the AP Chemistry exam. Also, the rate lab performed today (Thursday, February 10th, 2011) will be a formal lab write-up that will be due Monday, February 14th, 2011. See me before the test if you have any final questions.

Chapter 13 Test

On Monday, January 24th, 2010 the Chapter 13 Test will be given in class. The test will consist of 21 multiple choice questions and three free response questions. Please make sure to go over the practice exam given out last week in class. A solutions guide is supplied on the Events Calendar under the date January 18th. You will be supplied with an equations sheet and periodic table from the AP Chemistry exam. Please look over the highlights below of what you should have committed to memory before the exam.

Know the now BIG FIVE solubility rules.

1. All nitrate ionic compounds are soluble.
2. All alkali ion (group 1A of the periodic table) ionic compounds are soluble.
3. All ammonium (NH4^+1) ionic compounds are soluble.
4. All chloride (Cl^-1), bromide (Br^-1), and iodide (I^-1) ionic compounds are soluble except for silver ion (Ag^+1) and lead (II) ion (Pb^+2) compounds.
5. All acetate (C2H3O2^-1 OR CH3COO^-1) ionic compounds are soluble except for silver ion (Ag^+1) and mercury (I) ion (Hg^+1) compounds.

Knowledge of the solubility rules can be applied in a number of different ways. If a compound does not fit the solubility of one of the rules above, assume the substance to be insoluble (solid forms).

For spectrophotometry (light absorbance) to be applicable for concentration determination, remember that the solution must be colored. A good rule of thumb is if a compound contains a transition metal, it is colored. (The exceptions to this rule being silver and zinc.)

Study hard. This is the first test of the semester, so it will be a major portion of your grade.