Monday, February 28, 2011
Mon-Day 2
Physics - we reviewed the various rules for determining the magnetic force field lines that show the direction of force on a NEGATIVE charge/electron or the direction of force on a compass needle (where its north pole would point).
We then began some of the packet problems.
AP Chem- UNIT EXAM ON EQUILIBRIUM is on WEDNESDAY. STUDY EVERY PAGE OF NOTES. DO EVERY PRACTICE PROBLEM. REVIEW ALL TUTORIALS. If you do not do well on this exam, you will likely do worse on the upcoming, more challenging equilibrium unit exams.
Today, we continued some pH estimation problems, and saw that for STRONG ACIDS, the concentration given for the strong acid is EQUAL to the hydronium ion concentration at equilibrium because the strong acid is 100% ionized.
We discussed the TWO factors that determine acid strength:
1. The polarity of the H-X bond: the more polar, the more that the H is like H+, the stronger the acid.
2. The strength of the H-X bond: the stronger the bond, the more energy required to break the H+ ion from the shared electrons in the bond, the WEAKER the acid (HF is a good example of such an acid).
We discussed how, in oxoacids, the more electron-attracting/withdrawing O atoms that are attached to the central atom, the more POLAR the O-H bond is, thus the stronger the oxoacid.
We then began some of the packet problems.
AP Chem- UNIT EXAM ON EQUILIBRIUM is on WEDNESDAY. STUDY EVERY PAGE OF NOTES. DO EVERY PRACTICE PROBLEM. REVIEW ALL TUTORIALS. If you do not do well on this exam, you will likely do worse on the upcoming, more challenging equilibrium unit exams.
Today, we continued some pH estimation problems, and saw that for STRONG ACIDS, the concentration given for the strong acid is EQUAL to the hydronium ion concentration at equilibrium because the strong acid is 100% ionized.
We discussed the TWO factors that determine acid strength:
1. The polarity of the H-X bond: the more polar, the more that the H is like H+, the stronger the acid.
2. The strength of the H-X bond: the stronger the bond, the more energy required to break the H+ ion from the shared electrons in the bond, the WEAKER the acid (HF is a good example of such an acid).
We discussed how, in oxoacids, the more electron-attracting/withdrawing O atoms that are attached to the central atom, the more POLAR the O-H bond is, thus the stronger the oxoacid.
# posted by C @ 4:04 PM 
Monday, February 21, 2011
Winter Vacation!
Physics class average on parallel circuits was a 90, and the work shown on part II was a significant improvement from that on the series circuits exam. That's very good, and let's keep that streak going throughout the third quarter. :)
AP Chem assignment is now posted; be sure to also check out the descriptive chem help file, and all of the organic chem notes, tutorials, and tests - our tests will contain more and more organic naming and compounds built into the questions so, if you do not know the names, formulas and reactions, you won't be able to answer the questions.
There will also be some part II questions with answers posted.
AP Chem assignment is now posted; be sure to also check out the descriptive chem help file, and all of the organic chem notes, tutorials, and tests - our tests will contain more and more organic naming and compounds built into the questions so, if you do not know the names, formulas and reactions, you won't be able to answer the questions.
There will also be some part II questions with answers posted.
# posted by C @ 3:13 PM
Friday, February 18, 2011
Fri-Day 1
Physics - reviewed the various left-hand rules, focusing on loops of wire and solenoid coils of wire.
Those of you who took off on Friday will have to catch up with the notes on Blackboard, and at extra help.
AP Chem - we continued our acids/bases unit by learning how to quickly estimate pH and [H+]; these are just simple mathematical tricks that obviate the need for a calculator- this will be to your advantage on parts I and II of the AP exam.
Those of you who took off on Friday will have to catch up with the notes on Blackboard, and at extra help.
AP Chem - we continued our acids/bases unit by learning how to quickly estimate pH and [H+]; these are just simple mathematical tricks that obviate the need for a calculator- this will be to your advantage on parts I and II of the AP exam.
# posted by C @ 11:04 PM
Thursday, February 17, 2011
Thurs-Day 2
Physics - we discussed the various "left-hand rules" for determining the magnetic force field lines; in each rule, you align a part of your hand with the electric current, and the force line will be in some perpendicular direction from the current.
We drew the various force lines for each scenario, which would show the direction of the force on an ELECTRON placed in that force field.
AP Chem - we finished up the general equilibrium unit by doing two comprehensive problems:
we predicted and explained the Le Chat shifts for various stresses in a soluble salt (saturated solution) equilibrium, as well as a chemical equilibrium problem.
We confirmed the shift in the chemical equilibrium by comparing the initial reaction quotient, Q, with the equilibrium constant, K.
We the introduced our new unit on Acids and Bases.
We drew the various force lines for each scenario, which would show the direction of the force on an ELECTRON placed in that force field.
AP Chem - we finished up the general equilibrium unit by doing two comprehensive problems:
we predicted and explained the Le Chat shifts for various stresses in a soluble salt (saturated solution) equilibrium, as well as a chemical equilibrium problem.
We confirmed the shift in the chemical equilibrium by comparing the initial reaction quotient, Q, with the equilibrium constant, K.
We the introduced our new unit on Acids and Bases.
# posted by C @ 11:55 PM
Wednesday, February 16, 2011
Wednes-Day 1
Physics - Introduced the new unit on Magnetism, the other part of the "electromagnetic force"; magnetic forces are due to MOVING/SPINNING electrons/charges, whereas electric forces are due to STATIC/STATIONARY electrons/charges.
We saw how to draw the magnetic force field line around a bar magnet, using the mnemonic ANTS - Away from the North, and Towards the South!
We saw that magnetic force fields are caused by the unpaired electrons in atoms of a magnet, or by the moving electrons/current in a wire.
We finished up questions on the parallel circuits lab, and handed that in.
AP Chem - we applied Le Chatelier and explained via kinetics, solubility equilibria in which an undissolved salt is in equilibrium with its aqueous ions.
We showed that, using the equilibrium constant, Kc, we could predict the relative increase or decrease in ion concentrations EVEN IF we added a common ion to the solution.
We discussed how to predict an increase or decrease in solubility of a salt depending on whether it dissolves endothermically or exothermically.
We saw how to draw the magnetic force field line around a bar magnet, using the mnemonic ANTS - Away from the North, and Towards the South!
We saw that magnetic force fields are caused by the unpaired electrons in atoms of a magnet, or by the moving electrons/current in a wire.
We finished up questions on the parallel circuits lab, and handed that in.
AP Chem - we applied Le Chatelier and explained via kinetics, solubility equilibria in which an undissolved salt is in equilibrium with its aqueous ions.
We showed that, using the equilibrium constant, Kc, we could predict the relative increase or decrease in ion concentrations EVEN IF we added a common ion to the solution.
We discussed how to predict an increase or decrease in solubility of a salt depending on whether it dissolves endothermically or exothermically.
# posted by C @ 12:43 PM
Tuesday, February 15, 2011
Tues-Day 2
Physics - took the written response part of the Parallel Circuits exam.
Tomorrow, we begin the Magnetism unit!
AP Chem - discussed the Le Chatelier shift (or lack thereof) for each type of kinetic stress; we also discussed the addition of an inert gas to a system at constant T and V (no shift because the partial pressures of any gaseous reactants or products remain the same) as well as adding the inert gas at constant T and P (shift towards the side with more moles of gases).
We then discussed the EXPLANATION of Le Chat's simple rules via kinetic-molecular theory. These problems are much easier when you DRAW a picture of what is occurring in the reaction vessel before AND after the stress is applied; also, putting in effective collision rate numbers that are consistent with your picture leads you to the correct shift prediction.
Keep practicing the problems posted on Blackboard and be sure to go over the notes for the whole unit.
Tomorrow, we begin the Magnetism unit!
AP Chem - discussed the Le Chatelier shift (or lack thereof) for each type of kinetic stress; we also discussed the addition of an inert gas to a system at constant T and V (no shift because the partial pressures of any gaseous reactants or products remain the same) as well as adding the inert gas at constant T and P (shift towards the side with more moles of gases).
We then discussed the EXPLANATION of Le Chat's simple rules via kinetic-molecular theory. These problems are much easier when you DRAW a picture of what is occurring in the reaction vessel before AND after the stress is applied; also, putting in effective collision rate numbers that are consistent with your picture leads you to the correct shift prediction.
Keep practicing the problems posted on Blackboard and be sure to go over the notes for the whole unit.
# posted by C @ 8:56 PM
Monday, February 14, 2011
Mon-Day 1
We then finished the parallel circuit construction and measurements activity.
AP Chem - we did several permutations of gas-solid equilibrium problems in which we either determined the equilibrium concentrations of reactants and products or we determined the equilibrium constant based on initial conditions and the stoichiometry of the reaction (which we organize all in one ICE table).
We saw the important case in which solids or liquids are added to equilibrium solid-gas mixtures; adding a solid or liquid (not the solvent) changes NOTHING because solids and liquids are not part of any equilibrium constant expression. The ONLY change, of course, is that you have/see more of the unreacted solid that you just added to the container.
We discussed the 3-STEP Le Chatelier method for predicting shifts in systems.
This explains nothing but it is very useful in predicting whether or not a given stress will make more or less of a desired (or undesirable) reactant or product.
We will give the REAL kinetics explanation of HOW stresses CAUSE shifts. Once you know the real deal, Le Chatelier is convenient but superfluous.
# posted by C @ 8:52 PM
Friday, February 11, 2011
Fri-Day 2
Physics - we finished up the parallel circuits unit by working on multiple choice problems, and worksheet 7 questions. The remainder of the packet answers are posted on Blackboard.
AP Chem - took the unit exam on Kinetics.
AP Chem - took the unit exam on Kinetics.
# posted by C @ 11:58 PM
Thursday, February 10, 2011
Thurs-Day 1
Physics- we did several parallel circuit problems in worksheet 6, determining the number of resistors required to get a particular Req. We saw that with each resistor connected in parallel, the net resistance of the circuit decreases (the opposite of a series circuit).
We then went through the initial setup of our more difficult parallel circuits lab.
AP Chem - solved equilibrium problems using the ICE table organizer.
We then went through the initial setup of our more difficult parallel circuits lab.
AP Chem - solved equilibrium problems using the ICE table organizer.
# posted by C @ 11:12 PM
Wednesday, February 9, 2011
Wednes-Day 2
Physics - continued with more parallel circuit problems; these problems involved switches, and calculations of individual circuit loop currents, as well as equivalent resistance and total current.
We continue to stress that each loop has the same potential difference as the total voltage of the battery; we also emphasize that each loop is completely independent of the others, and that Ohm's Law applies to each individual loop, as well as to the whole circuit, as long as the appropriate SUBSCRIPTS are used.
Do not use just generic V, I , and R in these calculations or you will make an error.
AP Chem - took the unit kinetics exam. I am already appalled at the number of students who showed NO WORK in trying to deduce the rate law from the data table! Every single problem that we did in class emphasized that you had to DIVIDE one experiment's rate law data by another, and then repeat the process for the other exponent. You CANNOT do these problems in your head on the AP exam; you must show detailed work/thought process on EVERY written response answer.
We continue to stress that each loop has the same potential difference as the total voltage of the battery; we also emphasize that each loop is completely independent of the others, and that Ohm's Law applies to each individual loop, as well as to the whole circuit, as long as the appropriate SUBSCRIPTS are used.
Do not use just generic V, I , and R in these calculations or you will make an error.
AP Chem - took the unit kinetics exam. I am already appalled at the number of students who showed NO WORK in trying to deduce the rate law from the data table! Every single problem that we did in class emphasized that you had to DIVIDE one experiment's rate law data by another, and then repeat the process for the other exponent. You CANNOT do these problems in your head on the AP exam; you must show detailed work/thought process on EVERY written response answer.
# posted by C @ 2:31 PM
Tuesday, February 8, 2011
Tues-Day 1
Physics - we did all of Circuits 5 on parallel circuits, and then we set up series circuits, and determined that each resistor in the circuit obeyed Ohm's Law.
AP Chem - started with a review of equilibrium constant expressions in terms of concentrations or in terms of partial pressures of gases (if any).
Large K values indicate that the PRODUCTS are "favored" at EQUILIBRIUM.
Small K values indicate that the REACTANTS are "favored" at EQUILIBRIUM.
We saw that, when the equation stoichiometric coefficients are multiplied by a given factor, x, that the resulting equilibrium constant is taken to that EXPONENT, x.
When the products and reactants are written in reverse, the resulting K is the RECIPROCAL of the original K.
We also showed how to combine the equilibrium constants from several reactions; addition of reactions causes the MULTIPLICATION of the respective equilibrium constants to get the NET equilibrium constant for the overall reaction.
We discussed "REACTION QUOTIENT" which is the same EXPRESSION as K , HOWEVER, the quantities plugged in to the expression are NOT the equilibrium concentrations! The quantities plugged into the expression are the INITIAL concentrations.
By comparing K with Q, one can determine whether the reaction will proceed towards either forming more reactants or more products as equilibrium is approached.
AP Chem - started with a review of equilibrium constant expressions in terms of concentrations or in terms of partial pressures of gases (if any).
Large K values indicate that the PRODUCTS are "favored" at EQUILIBRIUM.
Small K values indicate that the REACTANTS are "favored" at EQUILIBRIUM.
We saw that, when the equation stoichiometric coefficients are multiplied by a given factor, x, that the resulting equilibrium constant is taken to that EXPONENT, x.
When the products and reactants are written in reverse, the resulting K is the RECIPROCAL of the original K.
We also showed how to combine the equilibrium constants from several reactions; addition of reactions causes the MULTIPLICATION of the respective equilibrium constants to get the NET equilibrium constant for the overall reaction.
We discussed "REACTION QUOTIENT" which is the same EXPRESSION as K , HOWEVER, the quantities plugged in to the expression are NOT the equilibrium concentrations! The quantities plugged into the expression are the INITIAL concentrations.
By comparing K with Q, one can determine whether the reaction will proceed towards either forming more reactants or more products as equilibrium is approached.
# posted by C @ 11:18 PM
Monday, February 7, 2011
Mon-Day 2
Physics - introduced a different type of circuit: the parallel circuit, and examined how the current gets split at each parallel branch in the circuit. The circuit basically consists of two or more completely independent loops that are connected to the voltage source as if each was the only part of the circuit.
The difficult calculation is getting the overall equivalent resistance of the circuit, which decreases with each resistor added in parallel.
AP Chem -
Kinetics exam on Wednesday.
Expect the following question types:
Complete explanation of HOW each factor that can affect the rate of a reaction does so:
Explanation must be in terms of collision frequency, fraction of particles with proper orientation for an effective collision, fraction of molecules that meet or exceed the activation energy for an effective collision, and overall effective collision frequency. You should use made up numbers in your explanation.
Calculation of rate of reaction (from graphs or data) from rate of appearance or disappearance of products or reactants, respectively.
Determination of rate law, order of reaction overall, and for each reactant, from data table and from graphed data.
Assessing the plausibility of reaction mechanisms, after the rate law has been experimentally determined, and relating the rate law to the mechanism.
Determination and explanation of catalysts and intermediates in reaction mechanisms.
Explanation/determination of catalysts and intermediates on energy/enthalpy diagrams.
Time-dependent rate law calculations from data tables, graphs, or time/concentration data.
Using the two versions of the Arrhenius equation to determine activation energy or rate constant at a second temperature, given graphs or data table of rate constant vs. inverse temperature, or given appropriate data.
Knowledge of any graphical representation of any order rate law.
We reviewed equilibrium constant expressions in terms of concentrations or in terms of partial pressures of gases (if any).
Large K values indicate that the PRODUCTS are "favored" at EQUILIBRIUM.
Small K values indicate that the REACTANTS are "favored" at EQUILIBRIUM.
We saw that, when the equation stoichiometric coefficients are multiplied by a given factor, x, that the resulting equilibrium constant is taken to that EXPONENT, x.
When the products and reactants are written in reverse, the resulting K is
the RECIPROCAL of the original K.
We also showed how to combine the equilibrium constants from several reactions; addition of reactions causes the MULTIPLICATION of the respective equilibrium constants to get the NET equilibrium constant for the overall reaction.
The difficult calculation is getting the overall equivalent resistance of the circuit, which decreases with each resistor added in parallel.
AP Chem -
Kinetics exam on Wednesday.
Expect the following question types:
Complete explanation of HOW each factor that can affect the rate of a reaction does so:
Explanation must be in terms of collision frequency, fraction of particles with proper orientation for an effective collision, fraction of molecules that meet or exceed the activation energy for an effective collision, and overall effective collision frequency. You should use made up numbers in your explanation.
Calculation of rate of reaction (from graphs or data) from rate of appearance or disappearance of products or reactants, respectively.
Determination of rate law, order of reaction overall, and for each reactant, from data table and from graphed data.
Assessing the plausibility of reaction mechanisms, after the rate law has been experimentally determined, and relating the rate law to the mechanism.
Determination and explanation of catalysts and intermediates in reaction mechanisms.
Explanation/determination of catalysts and intermediates on energy/enthalpy diagrams.
Time-dependent rate law calculations from data tables, graphs, or time/concentration data.
Using the two versions of the Arrhenius equation to determine activation energy or rate constant at a second temperature, given graphs or data table of rate constant vs. inverse temperature, or given appropriate data.
Knowledge of any graphical representation of any order rate law.
We reviewed equilibrium constant expressions in terms of concentrations or in terms of partial pressures of gases (if any).
Large K values indicate that the PRODUCTS are "favored" at EQUILIBRIUM.
Small K values indicate that the REACTANTS are "favored" at EQUILIBRIUM.
We saw that, when the equation stoichiometric coefficients are multiplied by a given factor, x, that the resulting equilibrium constant is taken to that EXPONENT, x.
When the products and reactants are written in reverse, the resulting K is
the RECIPROCAL of the original K.
We also showed how to combine the equilibrium constants from several reactions; addition of reactions causes the MULTIPLICATION of the respective equilibrium constants to get the NET equilibrium constant for the overall reaction.
# posted by C @ 6:38 PM
Friday, February 4, 2011
Fri-Day 1
Physics - took the written response part of the series circuits exam.
AP Chem - went over another descriptive chem reaction - redox involving strong oxidizers , the dichromate ion, and the permanganate ion.
We then began our new unit on Equilibrium.
We showed and described physical and chemical equilibrium, saw the basis of the law of chemical equilibrium, how the discoverers of the relationship between equilibrium concentrations at a given temperature and the balanced equation coefficients made their finding.
We noted the two common equilibrium constant expressions in terms of equilibrium concentrations and in terms of equilibrium partial pressures.
AP Chem - went over another descriptive chem reaction - redox involving strong oxidizers , the dichromate ion, and the permanganate ion.
We then began our new unit on Equilibrium.
We showed and described physical and chemical equilibrium, saw the basis of the law of chemical equilibrium, how the discoverers of the relationship between equilibrium concentrations at a given temperature and the balanced equation coefficients made their finding.
We noted the two common equilibrium constant expressions in terms of equilibrium concentrations and in terms of equilibrium partial pressures.
# posted by C @ 11:02 PM
Thursday, February 3, 2011
Thurs-Day 2
Snow Delay Day - nothing.
# posted by C @ 11:01 PM
Wednesday, February 2, 2011
Wednes-Day 1
Physics - took the multiple choice part of our series circuits exam
AP Chem - discussed how and why catalysts work, heterogenous vs. homogeneous catalysts (just a definition); we then did two kinetics review problems in which we used a table of experimental data to determine the rate law of the reaction, and then we assessed the plausibility of proposed mechanisms for the reaction.
We also reviewed the IMFA/Colligative Properties exam, a very important test on which I saw the most unbelievable errors.
AP Chem - discussed how and why catalysts work, heterogenous vs. homogeneous catalysts (just a definition); we then did two kinetics review problems in which we used a table of experimental data to determine the rate law of the reaction, and then we assessed the plausibility of proposed mechanisms for the reaction.
We also reviewed the IMFA/Colligative Properties exam, a very important test on which I saw the most unbelievable errors.
# posted by C @ 11:42 PM
Tuesday, February 1, 2011
Tues-Day 2
Physics - completed the problems in Circuits 3; this gave us further practice relating resistance, current, voltage, energy, and power.
We also did another "number of electrons passing a point in the circuit" in a given amount of time (you can use either of the two formulas); the key is getting the charge, q, in Coulomb's by multiplying the current, I, by the time, t, first.
We did a resistance problem, given constant temperature, we need the resistivity of the wire/material, the length of the wire, and the cross-sectional area of the wire. The resistivities of various metals AT 20 degrees Celsius are given in the reference table. However, the resistivity (and thus resistance) of a metal will INCREASE with increasing temperature because the electrons will crash more frequently into more rapidly vibrating/higher temperature atoms, and thus be slowed down i.e. resistance will increase.
AP Chem - did two more examples of kinetics problems from mechanism to predicted rate law to check for consistency with experimental rate law. A proposed mechanism must pass BOTH the balanced equation requirement, and the consistency with experimental (rate law) requirement.
We noted that catalyst can appear in rate law equations even though catalysts do not appear in the net balanced equation. Catalysts are NOT spectators, they DO participate in the reaction pathway.
In contrast, intermediates that appear in a rate determining step would have to be substituted for in a rate law because there is no way to manipulate intermediate concentrations in a beaker at the start of the reaction (i.e. initial conditions).
In 10/11, we added to common redox reactions to our descriptive chemistry arsenal: those involving acidified solutions of dichromate ion or of permanganate ion (will introduce this in 4/5 tomorrow).
We began to go over some of the unbelievable misconceptions, and test-taking errors in order to improve your performance on all future tests.
We also did another "number of electrons passing a point in the circuit" in a given amount of time (you can use either of the two formulas); the key is getting the charge, q, in Coulomb's by multiplying the current, I, by the time, t, first.
We did a resistance problem, given constant temperature, we need the resistivity of the wire/material, the length of the wire, and the cross-sectional area of the wire. The resistivities of various metals AT 20 degrees Celsius are given in the reference table. However, the resistivity (and thus resistance) of a metal will INCREASE with increasing temperature because the electrons will crash more frequently into more rapidly vibrating/higher temperature atoms, and thus be slowed down i.e. resistance will increase.
AP Chem - did two more examples of kinetics problems from mechanism to predicted rate law to check for consistency with experimental rate law. A proposed mechanism must pass BOTH the balanced equation requirement, and the consistency with experimental (rate law) requirement.
We noted that catalyst can appear in rate law equations even though catalysts do not appear in the net balanced equation. Catalysts are NOT spectators, they DO participate in the reaction pathway.
In contrast, intermediates that appear in a rate determining step would have to be substituted for in a rate law because there is no way to manipulate intermediate concentrations in a beaker at the start of the reaction (i.e. initial conditions).
In 10/11, we added to common redox reactions to our descriptive chemistry arsenal: those involving acidified solutions of dichromate ion or of permanganate ion (will introduce this in 4/5 tomorrow).
We began to go over some of the unbelievable misconceptions, and test-taking errors in order to improve your performance on all future tests.
# posted by C @ 2:24 PM
