Class Video
Click on the date below to view the lecture video. NOTE: It will take 30 seconds or so to load the video. If you are on a connection off campus, it may take longer. I recommend viewing the videos while you are on campus.
Video from Spring 2018
We continued our discussion on initial rates and rate laws in today's class. We determine the order for a reaction in a problem from the DCI workbook on page 7. We determined the order of each reactant, the rate constant and the units on the rate constant. Next we discussed the integrated rate laws for simple reactions that follow first order or second order kinetics. We discuss plotting data in graphs and what to look for in the plot and how to determine the rate constant from the slope of the graph. We ended class with discussion of half-lives for first and second order reactions. Right at the end of class Dr. Gelder shared some of his accumulated wisdom.
The video for this lecture is available between 18 hours and 36 hours following lecture.
The video for this lecture will be available between 18 hours and 36 hours following lecture.
The video for this lecture is available between 18 hours and 36 hours following lecture.
The video for this lecture will be available between 18 hours and 36 hours following lecture.In this class we began with a discussion of Exam III. We completed the practice balancing oxidation-reduction reactions using the half-reaction method. Next we looked at a Flash simulation and built several different examples of electrochemical cells. Many new words were introduced: electrode, anode, cathode, salt bridge, cell potential, and E°cell = E°cathode - E°anode. We also discussed the relationship between cell potential and thermodynamic favorability.Near the end of class the standard hydrogen electrode was introduced and we were using that information to generate the reduction potentials for other half-reactions.
In this class oxidation-reduction reactions were introduced. We discussed how we have already discussed some aspect of oxidation-reduction reactions. We looked at a set of oxidation-reduction reactions to discover identifiable characteristics of oxidation-reduction reactions. Presence of an element in its standard state in the reactants or products, or the loss or gain of oxygen atoms around another atom. Next we practiced balancing oxidation-reduction reactions in acidic and basic solution.
The video for this lecture is available.
The video for this lecture is available
We began with several clicker questions. Next we looked at two titration curves, one for a strong acid/strong base titration and then at a weak acid/strong base titration curve. Next we discussed calculating the pH of the solution after adding 5 mL of base past the end point. Then we began discussing calculations of weak acid/strong base titration. We did a calculation before adding any base, after adding some base and the last calculation was at the equivance point.
We began discussing how to calculate the pH of a common ion system: in this case the pH of a solution containing a weak base and its conjugate acid. Next we reviewed ALL of the types of pH calculations that we have been doing: strong acid, weak acid, strong base, weak base, salts (SA/SB, WA/SB and SA/WB) and common ion solution. Finally we started talking about titration curves, beginning with a strong acid/strong base titration.
In this class we discussed how to calculate the pH of salt (salt of a strong base/weak acid and a salt of a strong acid/weak base) solutions. Then we did an example of a weak acid and its salt (common ion).
The video for this lecture will be available between 18 hours and 36 hours following lecture.
ThClass began with a discussion of Exam II and some of the more difficult problems on Exam II. Next we continued with a disscuss ion acid-base equilibria. We reviewed Arrhenius acids and bases and Bronsted-Lowry acids and bases. We worked one of two types of problems in class. Given the initial concentration of an acid and the equilibrium constant we calculated the pH of the solution.
The video for this lecture will be available between 18 hours and 36 hours following lecture.
The video for this lecture will be available between 18 hours and 36 hours following lecture.
The video for this lecture will be available between 18 hours and 36 hours following lecture.We began with a clicker question on equilibrium constant expression for a particular reaction. We continued with a discussion of the equilibrium constants, the equilibrium expression and solving equilibrium problems using ICE tables. We discussed two different types of equilibrium problems; the first problem uses initial amounts and an equilibrium amount to complete the ICE table and calculate the equilibrium constant for the reaction; the second problem uses initial amounts and the equilibrium constant to calculate the equilibrium amounts of the reactants and products.
No class. This is a day off because students are taking evening exams.
After two clicker questions we discussed the difference between ideal temperature change andthe ideal 'i' value (van't Hoff factor) for a solution as well as the experimental temperature change and the experimental 'i' value (van't Hoff factor) for a solution. For strong electrolytes differences between the ideal 'i' value (van't Hoff factor) for a solution and the experimental 'i' value (van't Hoff factor) for a solution are due to ion-pairing. Ion-pairing was discussed. Next we viewed a computer simulation of a chemical reaction and learned about how the reaction was reversible. Then we viewed several videos showing a reaction between Fe3+ and SCN- as a macroscopic example of a reversible reaction. We then performed several experiment using the computer simulation reaction and collected some data and invented the equilibrium constant for a chemical reaction.
University closed
University closed
We began class with a clickere question about mol fraction and weight percent. Next we continued our discussion of colligative properties. We did several sample problems using vapor pressure lowering ideas, then we discussed freezing point depression using the experimental data from BCE8 to develop the mathematical relationship between the change in freezing point and the molality of the solution. We did a sample calculation with freezing point depression and boiling point elevation. Near the end of class we used BCE9 to re-visit the idea that the change in freezing point, or boiling point, depends on the number of particles in the solution. So we have to know whether the solute is a strong, weak or non electrolyte.
After a clicker question over the solution process for an ionic compound dissolving in water we continued our discussion of using concentration definitions. We worked on several problems converting between different concentration expressions. Near the end of class we began a discussion of Colligative Properties: vapor pressure lowering, boiling point elevation, and freezing point depression.
In this class we began with several clicker questions about the first exam. We discussed several aspects of the exam, and grades as reported on the Personal Grades Page. Next we contined our discussion of the solution process to learn how to explain why mixing a solute and solvent might result in a heterogeneous or a homogeneous mixture. Near the end of class we started discussing solution concentration expressions: weight %, mol fraction, molality and molarity. We started doing a problem.
In this class we worked out a sample problem using the Clausius-Clapeyron equation that relates the vapor pressure and temperature for a pure liquid in equilibrium with its vapor. Next we started a discussion of solutions, solutes and solvents and how we predict with a particular solute and solvent, when mixed, could result in a heterogeneous or homogeneous solution.
We introduced vapor pressure and discussed the property ofa pure liquid in equilibrium with its vapor. We discussed how comparing the pressure exerted by a vapor, compared to the equilibrium vapor pressure allowed the determination of what phase or phases might be present in a container.
We discussed the boiling point activity from the beginning. We looked for connections between the substances and their boiling points. We saw that as the number of electrons, or the level of the valence electrons increased the boiling point for a nonpolar or a polar substance also increased. Intermolecular attractive forces that depend on the number or level of valence electrons are called London Dispersion forces. Next we looked at the boiling points of HF, H2O and NH3 who have the fewest number of electrons of their homologous series. We saw they have the highest boiling points, due to the strongest IMAF, hydrogen-bonding. We discussed the important structural feature of hydrogen-bonding and drew several examples of hydrogen-bonding interaction. We also looked at animation depicting LDf and hydrogen-bonding forces.
We continued our discussion of entropy and free energy. We worked a problem from a past exam that require us to think more deeply about how to solve the problem. We did not need to use any new mathematical equations but we had to think carefully about the data in the problem and how to answer the question. At the end of class an activity showing data of the boiling points of some different substances was distributed. The activity is available on your Personal Page.
We began class with a clicker question on formation reqactions, elements in their standard state forming one mole of product. Other reactions are also important because the first two questions on most CHEM 1515 exams are 1) predicting products and, 2) writing ionic and net ionic equations. We looked at the reactions in RPS.1 to see the types of equations that could appear. Next we discussed delta H, delta S and delta G of reaction. The mathematical equations that are used to calculate each value were written on the board and discussed. While it is not easy to predict the value of delta H for a reaction, students arre expected to be able to predict the sign of delta S, and support their claim with evidence. We need to take a 2 minute break half way through lecture to allow those who like to stand to allow blood flow.
Lisa McGaw taught the first class of the semester and began in Chapter 17 Free Energy and Thermodynamics with a review of delta H˚(enthalpy) for chemical reactions. She began with the investigation of a chemical reaction between sodium bicarbonate and acetic acid. The rection occurred so we can conclude that the reaction is thermodynamically favored. The baggie got cold as the reaction proceeded indicating that the delta H for the reaction is positive, endothermic. That the reaction ocurred means the entropy must also be positive. Lisa continued with a discussion of the new thermodynamic terms: entropy (delta S) and free energy (delta G). We discussed q(heat) and enthalpy and how to calculate both. Enthalpy and heat are related to the first law of thermodynamics. Following the discussion of enthalpy and heat she discussed a new thermodynamic term, called entropy. We defined entropy in terms of the dispersal of position and energy in a system. We discussed the concept of dispersal for the solid, liquid and gaseous phase. Substances in the gas phase have more dispersion in terms of position and energy, compared to solids.
This was the first lecture of the semester and we discussed the structure of the course, grading, and the class web site. Checkout the PowerPoint for Tuesday's class on the Assignment Page Week 1.
Video from Spring 2017
This was the first lecture of the semester and we discussed the structure of the course, grading, and the class web site. Checkout the PowerPoint for Tuesday's class on the Assignment Page Week 1.
We began class with a clicker question on formation reactions (very important). After the clicker question we began in Chapter 17 Free Energy and Thermodynamics with a review of delta H˚(enthalpy) for chemical reactions. We discussed q(heat) and enthalpy and how to calculate both. Enthalp and heat are related to the first law of thermodynamics. Following the discussion of enthalp and heat we discussed a new thermodynamic term, called entropy. We defined entropy in terms of the dispersal of position and energy in a system. We discussed the concept of dispersal for the solid, liquid and gaseous phase. Substances in the gas phase have more dispersion in terms of position and energy, compared to solids.
Again we began with a clicker question on calculating the delta S˚ for a balanced chemical equation. We continued our discussion on entropy discussing how we can predict the sign of the entropy change for a chemical reaction. We also discussed how to explain such a preduiction. Next we did a very qualitative discussion of the delta S of the universe, which we referred to as delta G (free energy) as a measure of whether a reaction is thermodynamically favored or not. If delta G for a reaction is negative, the reaction is thermodynamically favored. If delta G for a reaction is positive, the reaction is thermodynamically favored. We discussed the mathematical relationship delta G = delta H - T*delta S and how delta G depends on temperature.
We finished our discussion of the 2nd and 3rd law of thermodynamics and began a discussion on intermolecular attractive forces.
Be began class with a clicker question to see how many remember how to determine whether a compound is polar or not polar. Next we looked a boiling point data to look for patterns that we might understand in terms of intermolecular attractive forces. We discussed three intermolecular attractive forces: hydrogen bond force, dipole dipole forces and London dispersion forces also know as LDF. We looked at some cool simulations and movies that provided dynamic views of the different types of intermolecular attractive forces. We discussed predicting which IMAF are present in a particular compound and we discussed how to explain why a particular substance might have a higher boiling point compared to another substance.
We began class with two clicker questions identifying intermolecular attractive forces in compounds. Next several students asked followup questions on intermolecular attractive forces. Following those questions we began a discussion of vapor pressure, and pressure due to vapor.
Be began class with a clicker question to provide some suggestsion of where resources were for Exam I. Next we discussed to the ACA and discussed one of the questions on calculating the temperature for a liquid given the vapor pressure. We used the Clausius-Clapeyron equation. Next we started a new chapter on solutions. We began a discussion, based on the BCE, about what properties of the compoenents of a mixture were important for determining whether a solution would result. We discussed the polarity of the components and the type(s) of intermolecular attractive forces. We then looked at some simulations to determine how to think about the solution process. We discussed the thermodynamics of the ssolution process in terms of free energy, enthalpy and entropy, delta G = delta H - T*delta S .
We discussed the first exam and asked a number of clicker questions about the exam. Next we discussed the solution process in terms of the change in enthalpy and the change in entropy. There is a different in the terms that make up the enthalpy factor in liquid-liquid solutions and solid/liquid solutions. We discussed these differents. Differentiation was made between using rules to predict whether a solution would form upon mixing two components, and the thermodynamic explanation for why a heterogeneous or homogeneous mixture is observed.
We began with a review of Thursday's discussion of the solution process through a clicker question. Next we discussed four different concentration expressions: weight percent, mol fraction, molality and molarity. We discussed several questions converting between different concentration expressions for the same solution. Near the end of class we began a discussion of colligative properties. Colligative properties are properties of solutions that depend on the number of particles. We discussed vapor pressure and discussed vapor pressure lowering in terms of the change in entropy.
We began with a clicker questions on concentration expressions. We discussed vapor pressure lowering and boiling point elevation and freezing point depression. We discussed vapor pressure lowering in terms of the entropy change experienced by a pure liquid to vapor
After a clicker question we looked at some additional data measuring the freezing point of solutions of ionic compounds and found that the depression in freezing point was greater for strong electrolytes compared to non-electrolytes. We discussed ideal freezing points and experimental freezing points. We modified the equation to calculate the freezing point lowering, ∆Tf = ikfm and ∆Tb = ikbm. We discussed ion-pairing and how it can explain the difference between an ideal freezing point and an experimental freezing point.
After a clicker question we took a conceptual approach to understanding properties of reversible reactions. We looked at several videos that showed the reaction between Fe(NO3)3(aq) and KSCN(aq) to form the complex ion FeSCN2+(aq). Then we investigated the reaction between R(g) and BG(g). We constructed ICE tables to track the initial amounts of reactants and products and the final amounts of reactants and products. From that information we were able to calculate the Change amounts of the reactants and products. Next we consider several experiments and discovered that the final amounts in a reversible reaction produced a constant that was called the equilibrium constant.
After several clicker questions reviewing solution questions we worked on questions in the During Class Inventions workbook beginning on page 31. We discussed equilibrium expressions and did several problems practicing calculating the magnitude of the equilibrium constant for a reaction given the initial amounts of all species and one equilibrium amount. Next we looked at a new type of equilibrium problem where we are given the initial amounts of all species and the equilibrium constant and we calculated the equilibrium amounts.
We discussed the results of Exam II and several clicker questions were answered. We then continued our discussion of gas phase equilibria doing calculations. The type of problems we focused on involved calculating the equilibrium amounts of reactants and products given the initial amounts and the magnitude of the equilibrium constant. Depending on the problem we ended up using the quadratic equation to solve the problem(s). Next we discussed Le Chatelier's principle. We reviewed the BCEs for 2/28/17 and 3/2/17 to see how changing the amounts of reactant or products, changing the temperature or changing the volume/pressure of a reaction at equilibrium will cause a shift in the position of equilibrium.
We began with some review of gas phase equilibria problems, no calculations, just some setup type problems as clicker questions. Next we did some straightforward Le Chatelier's principle clicker questions. Next I reviewed Le Chatelier's principle, but when into more dept when considering volume changes and temperature changes, so be sure to look over the DCI questions. Near the end of class we started discussing strong acids, weak acids, strong bases and weak bases. Everyone needs to be able to look at the formula of an acid or a base and know if the substance is strong or weak, acid or base. That will be critical! I just started describing Arrhenius acids when class time ran out.
Following several clicker questions we discussed Arrhenius definition and Bonsted-Lowry definitions of acids and bases. We calculated the pH for a strong acid and a strong base. Near the end of class we looked at data that would allow us to calculate the magnitude of the equilibrium constant for a weak acid or a weak base.
Due to technical difficulties there is no video for class on Tuesday, March 21, 2017. Scroll down to Thursday, March 3, 2016 and also Tuesday, March 8, 2016 for a video of classes taught in 2016 that would contain content similar to what was covered in this class.
Video will be available approximately 18 hours after class is finished.
We discussed the titration of a strong acid with a strong base. We did several calculations at various points along the titration curve
We discussed the titration of a weak acid with a strong base. We did several calculations at various points along the titration curve.
Introduced buffer solutions (common ion) by defining buffers and doing several calculations. We calculated the pH of a buffer and then calculated the pH after adding a small amount of a strong acid to the buffer. We also calculated the change in pH of water after adding a small amount of a strong acid.
We began with a discussion of the exam, and then continued with buffers. The discussion focused on what happens if the amount of strong acid or strong base that is added to the buffer results in 'destroying' the buffer. While we did not do any calculations you have those kind of calculations on Problem Set 11. We also discussed how to prepare a buffer solution. We discussed the optimum concentrations for the componenets of a buffer and how to determine which reagents work for a buffer of a particular pH. Near the end of class .
Video will be available approximately 18 hours after class is finished.
Video will be available approximately 18 hours after class is finished.
Video will be available approximately 18 hours after class is finished.
Video will be available approximately 18 hours after class is finished.
Video will be available approximately 18 hours after class is finished.
Video will be available approximately 18 hours after class is finished.
We discussed the ACA from Thursday's class (4/27/17) and the BCE to clear up some errors. Next we discussed the temperature dependence of the rate of a reaction. We talked about reaction coordinate diagrams and how increasing temperature increased the speed of particles which translated to more collisions, and more collision with sufficient energy (the activation energy) to be effective. We discussed the relationship between the rate constant, activation energy and temperature: ln(k2/k1) = -Ea/R(1/T2 - 1/T1). Be sure to review the DCI workbook for sample problems using this relationship on pages 19 - 21. Next we re-visited mechanism of chemical reactions in more detail and related the mechanism to the experimental rate law and the overall balanced chemical equation. Again review the DCI workbokk for examples of these types of problems, pages 23 - 26.
Video will be available approximately 18 hours after class is finished.
Here is a review for Exam 1 from CHEM 1515 Spring 2008. I recommend pausing the video after each question is read, and trying to answer the question, then listen to the 'Expert's' answer.
Here is a review for Exam 2 from CHEM 1515 Spring 2008 .I recommend pausing the video after each question is read, and trying to answer the question, then listen to the 'Expert's' answer.
Here is a review for Exam 3 from CHEM 1515 Spring 2008 .I recommend pausing the video after each question is read, and trying to answer the question, then listen to the 'Expert's' answer.
Video from Spring 2016
This was the first lecture of the semester and we discussed the structure of the course, grading, and the class web site. Checkout the PowerPoint for Tuesday's class on the Assignment Page Week 1.
We began our discussing on Chapter 17 with a brief review of ethalpy, exothermic reactions and endothermic reactions and calculation the enthalpy change for a chedmical reaction. Next we talked about entropy. We discussed the important criteria for entropy in terms of physical state of a substance. We discussed the entropy change for a chemical reaction and how to predict whether the sign of the change in entropy is positive or negative. We discussed the term dispersal and how it is important for understanding entropy and entropy change. At the end of class we looked at the mathematical equation for calculating the change in entropy for a chemical reaction.
We will continue our discussion of Chapter 17. We began with a discussion of the ACA from Thursday, January 14th class. In particular we talked about the important of formation reactions, and my expectation that students are able to write the formation reaction (with phases) for any compound I ask! We also talked about predicting the sign of the 
S° for a reaction. What is most important is being able to explain the sign of S°. Explaining is important. Check out the lecture to see what kind of an explanation I will expect. We practiced predicting S° for a few reactions. Next we calculated the S° of the universe, and related thatto G° for a reaction. We are finished with PS#1. Next we will discuss Chapter 11, checkout BCE#3 for an idea of what we will be covering, and what prior knowledge is needed.
Initially discussed next week's laboratory covering Survival Organic Chemistry. Be sure to do the pre-lab questions for the experiment BEFORE coming to your laboratory class (that means before the recitation class also). I discussed graphing calculators were OK for CHEM 1515 exams. We did an entropy clicker question and I left you with a question based on the clicker question. On the clicker question you were asked to calculate the Sf° given Hf° and Gf° for CH3NH2. The correct answer for the Sf° for CH3NH2 was -189 J mol-1 K-1. In class I then asked everyone to calculate S° CH3NH2. You are welcome to use a table of Thermodynamic values posted on our class web site. Next we reviewed the ACA from Tuesday's class. We completed our discussion on the 2nd and 3rd law of thermodynamics and continued in a new chpater on Liquids. This chapter began with intermolecular attractive forces. We discussed the BCE and introduced the three important intermolecular attractive forces: hydrogen-bonding, London Dispersion forces and dipole-dipole forces.
We continued our discussion on intermolecular attractive forces discussing dipole-dipole forces. We discussed a process that was important to follow to determine the nature and strength of the intermolecular attractive forces for a particular substance. We also discussed how to answer a question about comparing boiling points of two different substances. Near the end of class we introduce vapor pressure an important property of liquids. We talked about how vapor pressure is measured and what vapor pressure is in terms of a definition.
We reviewed the ACA and part of the BCE associated with vapor pressure of liquids and distinquished between the pressure due to the vapor and the equilibrium vapor pressure. The pressure due to the vapor can never exceed the equilibrium vapor pressure for a liquid at a given temperature. Also if the pressure due to the vapor is less than the equilibrium vapor pressure, omnly gas (vapor) can be present. Next we looked at how the vapor pressure changes with temperature and discovered a linear relationship between ln (vp) and 1/T(K). Be sure to check out the DCI for this class on your Personal Assignment page to see how to solve these types of problems.
We started Chapter 12 Solutions. We began with several animations showing the formation of solutions and we discussed (from the BCE) homogeneous and hetergeneous mixtures, specifically how to predict whether a mixture of two substances will form a homogeneous or heterogeneous mixture. The rule is based on polarity and intermolecular attractive forces. When the IMAF are the same a homogeneous mixture is produced, if they are different a heterogneous mixture is formed. Rules help us predict, but to explain a deeper understanding is required. For a molecular solute and molecular solvent we discussed ∆G˚ = ∆H˚ - T∆S˚. The ∆H˚ term is made up of three parts ∆Hsolute-solute, ∆Hsolvent-solvent and ∆Hsolute-solvent. When the heat released in ∆Hsolute-solvent is greater than the sum of ∆Hsolute-solute and ∆Hsolvent-solvent the ∆H term is exothermic. ∆S is always (for our purposes) positive. So when ∆H is negative and ∆S is positive it is thermodynamically favored to form a homogeneous mixture. Right at the end of class concentration expressions were introduced: molarity, molality, mol fraction and weight percent.
We reviewed the ACA and the BCE. Everyone demonstrated their ability to correctly predict the polarity of a compound and whether a mixture of two substance would be homogeneous or heterogeneous. So we continued our discussion of the solution process in the case of an ionic solute added to water. We still consider ∆G˚ = ∆H˚ - T∆S˚. However, the ∆H˚ term is made up of two parts ∆Hlattice energy(solute-solute)and ∆Hhydration energy (∆Hsolvent-solvent and ∆Hsolute-solvent). Heat is released in ∆Hhydration energyand heat is absorbed in ∆Hlattice energy. Whether the ∆H term is exothermic or not depends on the values of the lattice energy and the hydration energy. ∆S is always (for our purposes) positive. So when ∆H is negative and ∆S is positive it is thermodynamically favored to form a homogeneous mixture. Next we discussed molarity, molality, mol fraction and weight percent and did several sample calculations.
We began with a quick review of molarity, molality, mole fraction and weight percent. We next talked about ionic solids dissolving in water in terms of ∆G˚ = ∆H˚ - T∆S˚. Next we started talking about Colligative properties, that is how the addition of a nonvolatile solute affects vapor pressure above the solution, the freezing point of the solution and the boiling point of the solution. Vapor pressure lowering was introduced by looking at data for the vapor pressure of the solvent above a solution. We then did several sample problems using vapor pressure. Next we looked at the BCE and talked about data that was collected for the freezing point after adding some solute to water. We looked at the pattern in the data to determine the relationship between ∆T and molality. We came up with the equation ∆Tf = kfm.
We began by doing a question where we calculated the freezing point and the boiling point for a particular solution. Then we did a similar clicker question of the same type. Next we looked at some additional data measuring the freezing point of solutions of ionic compounds and found that the depression in freezing point was greater for strong electrolytes compared to non-electrolytes. We discussed ideal freezing points and experimental freezing points. We modified the equation to calculate the freezing point lowering, ∆Tf = ikfm and ∆Tb = ikbm.
We began with a clicker question on colligative properties asking about which solution has the higher boiling point. So we discussed the question. Next we reviewed the ACA for class on Thursday, February 11th. Halfway through the lecture I talked about how to access the Java applets that we will use this semester. I bulleted the steps that have to be followed. So we started a new chapter by looking at a particulate level simulation of the reaction: R + BG --> RG + B. We saw that the reaction is reversible. We next looked at the same reaction but using a different view where we viewed a chart recording that showed the initial amounts of the reaction and then how the reaction proceeded to a state where there is no further change. We did several experiments where we given initial amounts, and we predicted the ending amounts. We ended class with data from four experiments.
We continued with Tuesday discussion of the four experiments and we calculated the equilibrium constant for the reaction of R + BG --> RG + B. We then looked at the reaction, Fe3+ + SCN- --> FeSCN2+. We saw how the reaction behaves as an example of a reversible reaction. The characteristics are 1) there are appreciable amounts of all species in solution; 2) the reaction is dynamic in that is occuring in both directions; 3) that from a macroscopic level it appears to have stopped, but at the particulate level it is still ongoing in both directions.
We began with a clicker question on writing equilibrium constant expression that 81% of students got correct. We next looked at the ACA for last Thursday's class and discussed a particular problem. In the problem we were given the initial amounts and one equilibrium amount and asked to determine the other equilibrium amounts and the equilibrium constant for the reaction. We worked throught that example and then we looked at the second type of equilibrium problem where we are given the initial amounts and the equilibrium constant and we are asked to calculate the equilibrium amounts of all species. We discussed the two basic types of calculations that we do for equilibrium problems.
The non-equilibrium reaction quotient and its importance in determining the direction of a chemical reaction was introduced. We began class with a discussion of Le Chatelier's Principle, if a stress is imposed on a system at equilibrium, the reaction will proceed in a direction to relieve the stress and to re-establish equilibrium. We did several examples of how changes in concentration, pressure/volume and temperature can shift a reaction.
We began class with a discussion of the relationship between free energy and the equilibrium constant, G˚ = -RT ln K. We did a sample calculation. Next we started a new Chapter on Acids and Bases. The Arrhenius definition of an acid and a base was introduced along with the Bronsted-Lowry definition of an acid and a base. I introduced Kw = 1 x 10-14 = [H+][OH-] and pH = - log [H+]. We did a few calculations with these relationships.
We did several clicker questions over the 2nd hour exam and then did some pH and [H+] calculations. We then looked at the BCE where we had performed an experiment to measure the pH of several solutions of acids and bases. We calculated the equilibrium constant for a weak acid and a weak base. Next we calculated the equilibrium concentration for 0.200 M benzoic acid solution. Both of these problems are like problems on PS#9.
We began class with a discussion strong acids, weak acids, strong bases and weak bases. Based on the ACA students were having difficulty calculating pH so we practiced calculating the pH for a strong acid and a weak acid. Next we started talking about the acid-base properties of salts.
We discussed the steps we must follow for solving questions like, "Calculate the pH of 0.100 M ------." We had to identify the formula as that of a strong acid, weak acid, strong base or weak base; next we wrote the balanced chemical equation that described how the substance behaved, then write the equilibrium expressions and find or calculate K. Next we continued our discussion of salts. We classified salts as SA/SB, SA/WB, or WA/SB. We learned how to write the chemical equation that describes how the cation (SA/WB salt) or anion (WA/SB salt) behaves as an acid or base. We then learned how to calculate the equilibrium constant for the reaction since the K is not in the table of weak acid or weak base K's.
We began class with a discussion over strong acids, weak acids, strong bases and weak bases and salts (SA/SB salts, SA/WB salts and WA/SB salts). We then discussed common ion acid-base chemistry. A common ion is a solution that contains a weak acid and it salt (or its conjugate base), a solution with a weak base and its salt (or its conjugate acid), a solution of a strong acid and a weak acid, or a solution of a strong base and a weak base. We did several examples of common ion solution pH calculations. The interesting thing about common ion solutions is that there is the possiblility (in the first two cases) to use eith of two chemical equations to calculate the pH of the solution. Near the end of class we looked at neutralization reactions and discussed how to claculate the magnitude of the equilibrium constant for several types of neutralization reactions.
We tslked about the nine different types of pH calculations we have been doing and then dicussed neutralization reactions. Neutralization reactions have large equilibrium constants which means they go to completion. This meeans that when we set up an ICE table for a neutralization reaction we do not have to use 'x' in the Change row. We simply determine the limiting reagent in the Initial Row and use that in the CHange Row. After completing the ICE table for the neutralization reaction we can determine which of the nine systems the solution is and then proceed to calculate the pH of the solution. We did that for two types of neutralization reactions in class. the neutralization reaction of a strong acid and a strong base and the neutrlaization reaction for a weak acid and a strong base. To help with the problem set 10 and 11 I recommend printing out the DCI that we covered this week. Example problems are completely worked out for both of these neutralization reactions.
We reviewed neutralization reactions and titration curve and then started a discussion of buffers. We began a buffer calculation by calculating the pH of a buffer solution before adding any strong acid or strong base.
We completed the sample buffer calculation started on Tuesday, March 29th by adding a strong acid to the buffer. Then we added a strong base to the buffer solution and did that calculation. We also discussed how to identify the conjugate acid-base pair that could be used to make a buffer of a specified pH and what the concentrations of the buffer should be.
We discussed the BCE for today's class and introduced oxidation-reduction reacrtions. We identified two patterns that are common to many oxidation-reduction reactions: 1) the formation or the disappearance of a substance in it elemental form (comparing reactants to products); 2) an increase or decrease in the number of oxygen atoms (comparing reactants to products) around an atom in a compound. Balancing oxidation-reduction reaction in acidic and basic solutions was covered.
We looked at the ACA and the BCE to discuss oxidation-reduction reactions in more detail. Since redox reactions involve the transfer of electrons we looked at electrochemical cells that are constructed to take advantage of a thermodynamically favored redox reaction. By separating the oxidation and reduction half-reactions electrons can be used to do work.
We looked at the ACA and the BCE in terms of how to use a table of standard reduction potentials. We practiced calculating Eo (cell potentials) for redox reactions. We discussed the SRP table in terms of the laboratory activity during the week of April 4th. We also discussed how to calculate the change in free energy and the equilibrium constant for redox reactions.
We reviewed the ACA and the BCE in terms of how to use the Nernst equation. We determined Q, the number of electrons transferred so we can calculate Ecell. Near the end of class we discussed what half-reactions would occur in an electrolytic cell. Specifically we discussed the difference in the half-reactions if a molten salt is electrolyzed as opposed to an aqueous salt.
We began Chemical Kinetics today by considering a reaction and discussing a number of quantities we could determine just given the chemical equation. Following that discussion we looked at the chemical equation in a completely different way. This discussion lead us to talking about mechanisms of chemical reactions and a variety of new terms. We discussed the rate of a chemical reaction and reviewed how to determine the initial rate. We then considered the rate law for a chemical reaction and discussed the method of initial rates as a way to determine the experimental rate law.
Video from Spring 2014
This was the first lecture of the semester and we discussed the structure of the course, grading, and the class web site. Checkout the PowerPoint on the Assignment Page Week 1.
Thursday, January 16, 2014
No lecture (one of two classes returned to replace evening exams)
Began class by reviewing the BCE. We discussed predicting the sign of the enthalpy for a chemical reaction, and how to calculate the enthalpy change for a chemical reaction. This was important as there are several questions on PS1 covering enthalpy. Next entropy was introduced. We discussed how to predict the change in entropy (the sign of the entropy change) for a chemical reaction. The mathematical equation for calculating the entropy change was also provided. Checkout the ACA for Tuesday, January 21st to practice calculating the entropy change.
We began with a discussion on the ACA reviewing formation reactions and predicting S˚rxn. Next we developed the Gibbs-Helmholtz equation which says, G˚rxn = H˚rxn -TS˚rxn. We discussed the sign of G˚rxn and what the sign means. We then discussed the importance of temperature on the free energy of a reaction.
Began class by reviewing the ACA and BCE. In the BCE we discussed the boiling point trends for three groups of substances. Next the three types of intermolecular attractive forces that can occur between molecules of covalent compounds were introduced. We reviewed polar and nonpolar compounds and which IMAF occurred in each class of compounds. We then discussed water, its unusually high boiling point and the nature of the IMAF (hydrogen-bonding) that exists between water molecules.
We began with a review of the ACA. We continued with a discussion on intermolecular attractive forces. In particular we discussed how to explain why, in a pair of molecules, one had a higher boiling point compared to the other. We discussed London dispersion forces, and polarizability in molecules. Near the end of class we started discussing vapor pressure of liquids. We used a barometer to determine vapor pressure.
Began class by reviewing the ACA and BCE. Looking at IMAF in the ACA and vapor pressure in the BCE. We discussed a problem similar to PS3.5 to apply ideas about vapor pressure. We then discussed the relationship between vapor pressure and temperature and developed a mathematical equation, called the Clausius-Clapyron equation.
Began class with a discussion of th first exam and then began talking about the BCE. We continued our discussion of the Clausius-Clapyron equation and did a second sample calculation. We also reviewed how to use Microsoft Excel to plot ln (vapor pressure) versus 1/temperature data to obtain the equation for the line. We discussed how to obtain the slope and intercept from the equation
Began class by reviewing the ACA and BCE. We watch a portion of a video which reviewed the three cubic crystal lattices; simple cubic, body-centered cubic and face-centered cubic. We then did two sample calculations to determine the radius of a metal atom, and to determine the molar mass of an unknown metal atom. Near the end of class we discussed ionic compounds and how we can obtain the formula of an ionic compound from the arrangement of ions in a unit cell.
Began class with a discussion of the ACA. We looked at discussed Structures of ionic compounds with different stoichiometries: CsCl, CaF2 and NaCl. We introduced solutions and defines solute and solvent, saturated, unsaturater and supersaturated solutions. We discussed the solution process in terms of the enthalpy and entropy of the process.
Began class by reviewing the ACA and BCE. We discussed the solution process in detail. We reviewed predicting whether two components will form a homogeneous or heterogeneous mixture. We covered the importance of the Hsolution and the Ssolution in explaining whether a mixture will be homogeneous or heterogeneous. We discussed mixtures formed when both componenets were covalent substances, and when one of the components was an ionic solid and the solvent is water. At the end of class molality, molarity, mol fraction and weight percent were defined and one problem was discussed.
Began class with a discussion of the ACA. We discussed the definition of molality, molarity, mol fraction and weight percent and how to express the concentration of a solution in any of these concentration expressions. We did several problems, then we discussed Colligative properties. We looked at the BCE and used the data generated from the BCE to arrive at a relationship between the change in freezing point and the molality of particles in the solution.
Began class by reviewing part of the BCE. We talked about how to write the equation for an ionic solid dissolving in water. Next we talked about vapor pressure and Raoult's Law and how the pressure of the solvent above a solution depends on the mole fraction of solvent. We did two sample problems using Raoult's Law equation. Next we reviewed freezing point depression and boiling point elevation and did several problems calculating the freezing point depression and boiling point elevation for solutions. We also discussed how the freezing point is depressed when the solute is an ionic compound.
Began class by reviewing the ACA. We did the calcualtions in the ACA as a review of freezing point and boiling point. Some students had neglected to include the ideal i value in their calculation. Next we discussed the difference between an experimental i value and the theoretical i value. We look at some experimental data and calculated the experimental i value and discussed what it means. Near the end of class we looked at several reactions. Several were irreversible reactions. The last reaction we viewed behaved very differently compared to the irreversible reactions. The last reaction was in fact a reversible reaction, so we discussed its characteristics.
Began class by reviewing part of the BCE. Next we watched several videos describing a chemical reaction to setup characteristics of a reversible reaction. Next we looked at a particulate animation of a reversible reaction and then explored a reaction to discover a relationship between the amounts of the reactants and products. We ended up discovering that there is a relationship between te amounts of reactants and products and it is called the equilibrium constant.
Began class by reviewing the exam taken on Wednesday. Then we discussed characteristic of equilibrium constants. We discussed the general equation for an equilibrium expression and looked at that expression for several chemical reactions. Then we looked at a particular type of equilibrium problem to calculate the magnitude of an equilibrium constant. Given the initial amounts of the reactants and products, and an equilibrium amount of a reactant or product we can calculate the magnitude of an equilibrium constant. We did several examples of this type of calculation.
Began class with a clicker question covering the type of equilibrium constant calculation that was discussed in class on Thursday, March 6th. Then a few words over the errors and misconceptions I saw in the ACA. Then we started a discussion of a second type of equilibrium problem calculation. In this type we are given the initial amount of the reactants and the products, and the magnitude of the equilibrium constant. We are to solve for the equilibrium amounts of all reactants and products. At the end of class we began a discussion of Le Chatelier's principle. We will continue that discussion in class on Thursday, March 13, 2014.
We finished up discussing how changes in concentration, volume and temperature affect the position of equilibrium. We did some calcualtion of equilibrium constants at different temperature and how to calculate the free energy for a reaction given the equilibrium constant.
In this class, the first following Spring Break we started discussing Arrhenius acids and bases, how to calculate pH and pOH and what Kw is for water.
Began class with a clicker question covering calculating pH of a solution given the [H+]. We reviewed Arrhenius and Bronsted-Lowry definitions of acids and bases. We looked at two type of calculations. The first is calculating the equilibrium constant for a weak acid or weak base given the initial concentration of the acid or base, and the pH. The second calculation involves determining the equilibrium concentration of hydrogen ion given the initial concentration of the acid or base and the equilibrium constant.
Began class
Began discussed the acid base character of salts and of solutions containing a weak acid and its conjugate base, or a solution of a weak base and its conjugate acid.
We discussed titrations of strong acids and strong base and titrations of weak acids and strong bases.
We discussed titrations of weak acids and strong bases. We covered what the titration curve looks like and how to calculate the pH of the solution before adding strong base, adding strong base before the equivalence point, at the equivalence point and beyond the equivalence point.
We discuss buffer solutions and how to prepare a buffer as well as how to calculate the pH change when a small amount of an acid or base is added to a buffer.
I introduced oxidation-reduction reactions, howto recognize them and how to balance in acidic and basic solutions.
Lisa McGaw taught class today and coveredelectrochemical cells and all of their features aw well as more electrochemistry including standard reduction potentials for half reactions and how to calculate overall cell potentials.
More oxidation-reduction reactions.
Last day of class.....sob! Finished up with the Nernst equation and electrolysis.
Video from Spring 2013
This was the first lecture of the semester and we discussed the structure of the course, grading, and the class web site. Checkout the PowerPoint on the Assignment Page Week 1.
Began class by reviewing the BCE. We discussed predicting the sign of the enthalpy for a chemical reaction, and how to calculate the enthalpy change for a chemical reaction. This was important as there are several questions on PS1 covering enthalpy. Next entropy was introduced. We discussed how to predict the change in entropy (the sign of the entropy change) for a chemical reactions. The mathematical equation for calculating the entropy change was also provided. Checkout the BCE for Tuesday, January 15th to practice calculating the entropy change.
We began with a discussion on the ACA then we did a short review of how to calculate H˚rxn and S˚rxn. Next we developed the Gibbs-Helmholtz equation which says, G˚rxn = H˚rxn -TS˚rxn. We discussed the sign of G˚rxn and what the sign means. We then discussed the importance of temperature on the free energy of a reaction.
Began class by reviewing the ACA and BCE. In the BCE we discussed the boiling point trends for three groups of substances. Next the three types of intermolecular attractive forces that can occur between molecules of covalent compounds were introduced. We reviewed polar and nonpolar compounds and which IMAF occurred in each class of compounds. We then discussed water, its unusually high boiling point and the nature of the IMAF (hydrogen-bonding) that exists between water molecules.
Here is a review for Exam 1 from CHEM 1515 Spring 2008.I recommend pausing the video after each question is read, and trying to answer the question, then listen to the 'Expert's' answer.
We began with a review of the ACA. We continued with a discussion on intermolecular attractive forces. In particular we discussed how to explain why, in a pair of molecules, one had a higher boiling point compared to the other. We discussed London dispersion forces, and polarizability in molecules. Near the end of class we started discussing vapor pressure of liquids. We used a barometer to determine vapor pressure.
Technical difficulties with this lecture. Checkout the video from CHEM 1515 in Spring 2010 below.
Since our class digital video for January 24, 2013 has technical difficulties I have posted a lecture from 2010. Checkout the last 10 to 15 minutes of this video for a discussion of pressure of the vapor and equilibrium vapor pressure.
We wstarted class by answering several clicker questions covering intermolecular attractive forces. Next we began a discussion of solids by defining different types of solids based on the types of attractive forces. We began with atomic solids which include, metallic, extended covalent and Group VIIIA. We finished up with molecular solids and ionic solids. We discussed some of the properties of each type and what substances belong to each. Next we introduced three cubic crystal lattices; simple cubic, body-centered cubic and face-centered cubic. We discussed how to determine the number of particles in each crystal system. We ended class doing a sample calculation to determine the density of a particular metallic element.
At the beginning of lecture we discussed Exam I and recognized the top four students. Next we continued discussing cubic systems. We watch a portion of a video which reviewed the three cubic crystal lattices; simple cubic, body-centered cubic and face-centered cubic. We then did two sample calculations to determine the radius of a metal atom, and to determine the molar mass of an unknown metal atom. Near the end of class we discussed ionic compounds and how we can obtain the formula of an ionic compound from the arrangement of ions in a unit cell.
Discussed the solution process and the importance of the enthalpy change and the entropy change. We discussed how we can use rules to predict whether a particular solute dissolves in a particular solvent, but how rules are not explanations. We discussed how to explain why a solute dissolves in a solvent by discussing the enthalpy change and the entropy change.
Lisa covered for me since I was out of town. She discussed more problems converting between weight%, mol fraction, molarity and molality. She introduced freezing point depression and boiling point elevation.
Continued our discussion of the solution process and introduced concentration expressions: weight %, mol fraction, molarity and molality
We began with a review of freezing point depression and boiling point elevation as it relates to the van't Hoff factor, 'i'. Next we discussed ACA11 and ACA12. We finished class by looking at examples of reversible and irreversible reactions.
Continued our discussion of reversible reactions. We collected some data for the reaction R+BG --> RG+B and discovered that the Ending amounts could be arranged to produce a constant. We invented the equilibrium constant for a reaction.
Tuesday, February 26, 2013
Class was cancelled by the University due to bad weather.
We learned about the equilibrium constant expression and what happens to the equilibrium constant and its expression when we changed the balanced chemical equation. We also calculated the magnitude of the equilibrium constant for several different reactions. At the end of class we looked at a problem where given the initial concentrations and the equilibrium constant we could calculate the equilibrium concentrations of all species.
We discussed Le Chathelier's principle and distinguished between rules and explanation. We started discussing aqueous equilibria and acids and bases. We discussed strong acids, strong bases and weak acids and weak bases.
We Discussed the Arrhenius definition of acids and bases and looked at the autoionization of water. We discussed pH and pOH and calculated pH given [H+] or [OH-]. We also measure the pH of a 0.100 M solution of a weak acid and calculated the Ka for the weak acid. We also discussed weak bases and introduced a new definition of acids and bases, called the Bronsted-Lowry definition.
We discussed the Bronsted-Lowry definition of acids and bases and the resulting competition between the two acids and bases in the chemical equation. We introduced conjugate acid-base pairs. We did several examples of how to calculate the equilibrium [H+] given the initial concentration of the acid or base and the equilibrium constant.
We discussed three classes of salts: salts of strong acids and strong bases; salts of SA and weak bases; and salts of weak acids and SB. specifically we looked at their acid base character. we did two problems of how to calculate the pH of a salt solution of a given concentration. At the end of class we looked at a common ion problem. This type of problem includes a weak acid and its conjugate base (in the form of a salt) or a weak base and its conjugate acid (in the form of a salt).
We discussed salts and common ion systems and near the end of class titrations. We looked how to recongize salts, how to separate the formula of a salt into its component ions, how to identify which ion affects the pH of the solution, how to write the chemical equation that represents the reaction, and how to obtain the equilibrium constant. Once we have the chemical equation and K, setting up the ICE table and calculating the pH should be routine. We also looked at common ion solution, how to write the chemical equation and we solved an example (of a weak acid and its conjugate base) two different ways. Near the end of class we looked at the titration curve of a weak acid and a strong base and identified important features of the titration curve.
We reviewed the different types of solutions, and then discussed titration experiments between strong acids and strong bases. We calculated the pH of the strong acid, before adding any base, and then we calculated the pH of the solution after adding some base. We calculated the volume required to reach the equivalence point and the pH at the equivalence point and after adding excess base, beyond the equivalence point.
We began with a discussion of calculating equilibrium constants given a balanced net ionic equation. Next we continued our discussion over titration experiments between weak acids and strong bases. We calculated the pH of the weak acid, before adding any base, and then we calculated the pH of the solution after adding some base. We calculated the volume required to reach the equivalence point and the pH at the equivalence point and after adding excess base, beyond the equivalence point. Be sure to check out the DCIs from your Personal Assignment page on Week 12.
We reviewed the different types of solutions, and then discussed buffers and how buffers behave when adding small amounts of strong acid or strong base.
We began with a discussion of how to recognize oxidation-reduction reactions. We defined oxidation and reduction in terms of transfer of electrons and then balanced oxidation reduction reactions. We looked at a galvanic cell and discussed the different components and how an oxidation-reduction reaction can do work.
We looked at the construction of a voltaic (or Galvanic) electrochemical cell. We discussed the following terms: anode, cathode, electrode, salt bridge, anode compartment, cathode compartment, oxidationa, reduction and electron flow. We performed several experiments using Dr. Greenbowe's simualtion and we measured the cell potential for four reactions. We used those reaction to develop a reduction potential table (Table of reduction half-reactions) and then defined the reduction of H+ as equal to zero and determined the relative reduction potentials for the other reactions. We talked about calculating cell potentials and predicting products for reactions.
We discussed how ions move in the salt bridge and the criteria used to identify a salt. We also used the table of standard reduction potentials to answer a variety of different questions about oxidation and reduction reactions. We related delta G (free energy) to the standard cell potential, and K, the equilibrium constant. Then we discussed how the cell potential changes under non-standard conditions using the Nernst Equation.
We looked at the ACA to review how to predict products of oxidation reduction reactions. We also calculate a cell potential under nonstandard conditions from the ACA. We then discussed electrolysis of pure ionic liquids, and then electrolysis of aqueous ionic solutions.
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