General Chemistry

17 Jul 2018

Stoichiometric Calculations: A General Chemistry Flipped Classroom Module

Submitted by Jack F Eichler, University of California, Riverside
Evaluation Methods: 

1) Performance on the pre-lecture online quiz

2) Performance on the in-class activity (clicker scores or hand-graded worksheet)

Evaluation Results: 

Students generally score on average 70% or higher on the pre-lecdure quiz, and on average 70% or more of students correctly answer the in-class clicker questions. As  noted in the worksheet answer key, question #4 generally gives students the most trouble as they may not yet have learned how to sum a series of reactions to yield an overall reaction. Instructors are encoruaged to do an example of this in the acitivty introduction. 

Description: 

This is a flipped classroom activity intended for use in a first semester general chemistry course. Students are expected to have prior knowledge in determining the molar mass of compounds, how to carry out mole/gram conversions, and how to write balanced chemical reactions. The activity includes: 1) pre-lecture learning videos that guide students through carrying out basic stoichiometric calculations, determining the limiting reactant, and determining the percent yield of a reaction; 2) a pre-lecture interactive tutorial that helps students learn the concept of limiting reactant; 3) pre-lecture quiz questions; and 4) an in-class activity that requires students to apply their knowledge of stoichiometry and limiting reactant in the real-world application of converting coal to liquid fuel.

 

Learning Goals: 

Students are expected to complete the following learning objectives:

a) using mole-gram conversions and mole-mole conversions to carry out stoichiometric calculations for balanced chemical reactions;

b) gaining appreciation for how stoichiometric calculations are used in real-world chemical reactions.

Prior to completing this activity, students will be expected to have learned how to use molar masses of elements and compounds to carry out mole-gram conversions, how to balance chemical reactions, and how to use balanced chemical reactions to carry out mole-mole conversions.

 

Equipment needs: 

Suggested technology:

1) online test/quiz function in course management system

2) in-class response system (clickers)

Corequisites: 
Subdiscipline: 
Topics Covered: 
Prerequisites: 
Course Level: 
Implementation Notes: 

Attached as separate file. 

Time Required: 
50-80 minutes
22 Jun 2018
Evaluation Methods: 

Discuss students responses with respect to the answer key.

Evaluation Results: 

This activty was developed for the IONiC VIPEr summer 2018 workshop, and has not yet been implemented.

Description: 

Inorganic chemists often use IR spectroscopy to evaluate bond order of ligands, and as a means of determining the electronic properties of metal fragments.  Students can often be confused over what shifts in IR frequencies imply, and how to properly evaluate the information that IR spectroscopy provides in compound characterization.  In this class activity, students are initially introduced to IR stretches using simple spring-mass systems. They are then asked to translate these visible models to molecular systems (NO in particular), and predict and calculate how these stretches change with mass (isotope effects, 14N vs 15N).  Students are then asked to identify the IR stretch of a related molecule, N2O, and predict whether the stretch provided is the new N≡N triple bond or a highly shifted N-O single bond stretch.  Students are lastly asked to generalize how stretching frequencies and bond orders are related based on their results.

 
Learning Goals: 
  1. Evaluate the effect of changes in mass on a harmonic oscillator by assembling and observing a simple spring-mass system (Q1 and 2)

  2. Apply these mass-frequency observations to NO and predict IR isotopic shift (14N vs. 15N) (Q3 and 4)

  3. Predict the identity of the diagnostic IR stretches in small inorganic molecules. (Q5, 6, and 7)

Equipment needs: 

Springs, rings, stands, and masses (100 and 200 gram weights for example).

 

Corequisites: 
Implementation Notes: 

Assemble students into small groups discussions to answer the questions to the activity and collaborate.

 

 

Time Required: 
Approximately 50 minutes
19 Dec 2017

Visual scaffold for stoichiometry

Submitted by Margaret Scheuermann, Western Washington University
Description: 

These five slides are intended to share a visual scaffolding that I developed to help my general chemistry students identify what calculations are needed to solve stoichiometry problems.

 

The visual scaffold involves writing the balanced equation and then under it drawing a table with two rows and enough columns so that there is one column under each reagent in the equation. The top row is labeled as "moles" and the bottom row is labeled as "measurable quantity". Students then write in any information about a specific reagent or product that was given and identify the quantity that the question is asking them to find. They then add a series of arrows to the table to generate a "map" of how to get from the information they are given to the information they need to find with each arrow representating a type of calculation that they have already seen and practiced. Vertical arrows represent a calculation between a measured quantity and a number of moles. Horizontal arrows in the top row represent calculations between moles of one substance and moles of another substance. Horziontal arrows in the "measured quantity" row are not allowed since those unit conversion factors are not readily available. 

 

Corequisites: 
Topics Covered: 
Prerequisites: 
Course Level: 
Learning Goals: 

A student should be able to determine the quantity of a reagent required or the quantity of a product produced in a reaction.

Subdiscipline: 
Related activities: 
Implementation Notes: 

The scaffolding begins with a review of the two types of calculations that are required for basic stoichiometry: converting between grams and moles, and converting between moles of one substance and moles of another substance using the coefficients of a balanced equation as unit conversion factors (slide 1).

Some ABCD card/clicker questions can be added here if students have not practiced these types of problems in class recently.

After introducing the visual scaffold (slide 2) I do an example problem or two on the board/overhead/doc cam (slide 3).

This is a good point to give students an opportunity to work on a practice problem or if the introduction to stoichiometry began part way through a class period, an exit question.

Next I introduce situations where it could take more than one calculation to get from the measured quantity to moles (slide 4). 

An example problem and/or practice problem and/or exit question can be added here.

The visual scaffold is also relevant for limiting reagent problems. I've included an example (slide 5/6) but limiting reagent is usually presented in a subsequent class period after some examples of the limiting reagent concept using sandwiches or something similar. 

Time Required: 
30-50 minutes. varies with the number of examples and practice problems
Evaluation
Evaluation Methods: 

I will usually do an exit question- a stoichiometry problem from the textbook- after either slide 3 or slide 4. I do not require students to use the visual scaffold if they are already comfortable with stoichiometry from a previous class but many choose to use it. Some students will include the tables from the visual scaffold as part of the work they show on exams, again without being prompted or required to do so. 

3 Jun 2017
Evaluation Methods: 

This LO was craeted at the pre-MARM 2017 ViPER workshop and has not been used in the classroom.  The authors will update the evaluation methods after it is used.

Description: 

This module offers students in an introductory chemistry or foundational inorganic course exposure to recent literature work. Students will apply their knowledge of VSEPR, acid-base theory, and thermodynamics to understand the effects of addition of ligands on the stabilities of resulting SiO2-containing complexes. Students will reference results of DFT calculations and gain a basic understanding of how DFT can be used to calculate stabilities of molecules.

 
Prerequisites: 
Corequisites: 
Learning Goals: 

Students should be able to:

  1. Apply VSEPR to determine donor and acceptor orbitals of the ligands

  2. Identify lewis acids and lewis bases

  3. Elucidate energy relationships

  4. Explain how computational chemistry is beneficial to experimentalists

  5. Characterize bond strengths based on ligand donors

Course Level: 
Implementation Notes: 

Students should have access to the paper and have read the first and second paragraphs of the paper. Students should also refer to scheme 2 and table 2.

 

This module could be either used as a homework assignment or in-class activity. This was created during the IONiC VIPEr workshop 2017 and has not yet been implemented.

 
Time Required: 
50 min
3 Jun 2017
Evaluation Methods: 

This was created during the IONiC VIPEr workshop 2017 and has not yet been implemented.

 
Description: 

This module offers students an introductory chemistry or foundational inorganic course exposure to recent literature work. Students will apply their knowledge of VSEPR and basic bonding to predict geometries of complex SiO2-containing structures. Students will gain a basic understanding of how crystallography is used to determine molecular structures and compare experimental crystallographic data to their predictions.

Prerequisites: 
Course Level: 
Corequisites: 
Learning Goals: 

Students will be able to:

  1. Describe the bonding in SiO2 and related compounds
  2. Apply bonding models to compare and contrast bond types
  3. Apply VSEPR to predict bond angles
  4. Utilize crystallographic data to evaluate structures
Implementation Notes: 

Students should have access to the paper and read the first and fourth paragraphs on the first page and the third paragraph on the second page. Students should also reference scheme 1 and figure 1.

 

This module could be either used as a homework assignment or in-class activity.

 
3 Jun 2017
Evaluation Methods: 

This learning object was created at the pre-MARM workshop in 2017 and as such has not been used in a classroom setting. The authors will update the learning object once they have used it in their classes.

Description: 

This module offers students in an introductory chemistry or foundational inorganic course exposure to recent literature. Students will apply their knowledge of Lewis dot structure theory and basic thermodynamics to compare and contrast bonding in SiO2 and CO2.

Corequisites: 
Course Level: 
Prerequisites: 
Learning Goals: 

Students should be able to:

  1. Describe the bonding in SiO2 and related compounds (CO2)

  2. Use Lewis dot structure theory to predict bond orders

  3. Apply bonding models to compare and contrast bond types and bond energies (sigma, pi)

  4. Characterize bond strengths based on ligand donors

Implementation Notes: 

Students should read the first paragraph of the paper prior to completing this learning object. They can be encouraged to read more of the paper, but the opening paragraph is the focus of this learning object.

Time Required: 
50 min
25 Mar 2017

KINETICS - Computations vs. Experiment

Submitted by Teresa J Bixby, Lewis University
Evaluation Methods: 

- determine the activation energy of a reaction from an energy diagram

- determine the rate constant for the reaction from the activation energy

- determine the rate law and rate constant for a reaction from experimental data

 

These Learning Objectives will be assessed on a subsequent exam.

Evaluation Results: 

Most students did not have a problem determining the rate constant from the activation energy (from an energy diagram). From what mistakes there were, the most common mistake was choosing the wrong starting energy (choosing the product energy rather than the reactant energy to start). Most students were also able to determine the rate constant from experimental data, especially if there were clearly 2 experiments where only one reactant concentration was doubled for each reactant. Changing the factor by which the reactant concentration changed (1.3 for example), or including experimental data where two reactant concentrations changed at the same time, seemed to cause more problems. 

Description: 

<p>This activity has students use Spartan to build an energy diagram for an SN2 reaction as a function of bond length. The activation energy can then be used to determine the rate constant for the reaction. After a few intoductory questions to orient general chemistry students to the organic reaction (with a short class discussion), the instructions lead them step-by-step to build the energy diagram for CH&lt;sub&gt;3&lt;/sub&gt;Cl + Cl- --&gt; Cl- + CH&lt;sub&gt;3&lt;/sub&gt;Cl. Any questions about how to use the program or descriptions of the levels of theory are given during the class period. The questions, class discussion, and Spartan tutorial for the first reaction can be compelted in one 50 min period.&nbsp;</p><p>The rest of the activity is completed as an assignment. Other anions attack CH&lt;sub&gt;3&lt;/sub&gt;Cl and students consider which product is more stable. They also compare the computational rate constant for OH- attacking with a rate constant determined from experimental data. They find that Spartan is good for molecular modeling but the absolute value of the energies of the transition states are inaccurate.&nbsp;</p><p>SN2 reactions with more complex molecuels may be more illustrative.&nbsp;</p><p>In the future we hope to develop this activity into an in-class prelab where then students can collect the experimental data on their own.&nbsp;</p>

Learning Goals: 

- use Spartan to build molecules and a transition state

- determine the activation energy of a reaction from an energy diagram

- determine the rate constant for the reaction from the activation energy

- determine the rate law and rate constant for a reaction from experimental data

- relate reactant and product energies to leaving group character

- compare computation to experiment

Prerequisites: 
Corequisites: 
Equipment needs: 

Need to have access to Spartan Student.

Topics Covered: 
Course Level: 
Subdiscipline: 
Implementation Notes: 

Building the transition state seems to be the most confusing part for General Chemistry students who have not used Spartan before. Encouraging them to limit twirling the molecule around a lot before they have completed this step seems to help. I intend to clarify these instructions before the next implementation. 

A different base molecule may yield better agreement with experimental data. This will aslo be explored before the next implementation.

Time Required: 
50 min + out-of-class assignment (~5 days)
18 Jan 2017

calistry calculators

Submitted by Adam R. Johnson, Harvey Mudd College
Description: 

I just stumbled on this site while refreshing myself on the use of Slater's rules for calculating Zeff for electrons. There are a variety of calculators on there including some for visualizing lattice planes and diffraction, equilibrium, pH and pKa, equation balancing, Born-Landé, radioactive decay, wavelengths, electronegativities, Curie Law, solution preparation crystal field stabilization energy, and more.

I checked and it calculated Zeff correctly but I can't vouch for the accuracy of any of the other calculators. 

Prerequisites: 
Corequisites: 
Learning Goals: 

This is not a good teaching website but would be good for double checking math

 

Implementation Notes: 

I used this to double check my Slater's rules calculations (and found a mistake in my answer key!)

20 Jun 2016

Chapter 2--Stanley Organometallics

Submitted by George G. Stanley, Louisiana State University
Description: 

Chapter 2 from George Stanley's organometallics course, Lewis Base ligands

 

this chapter covers halides, oxygen and nitrogen donor ligands

The powerpoint slides contain answers to some of the in-class exercises, so those are behind the "faculty only" wall. I share these with students after the class, but not before.

Everyone is more than welcome to edit the materials to suit their own uses, and I would appreciate being notified of any mistakes that are found.


Course Level: 
Subdiscipline: 
31 Mar 2016

Mix and Match Ligand Group Orbitals and Metal Orbitals

Submitted by ashoka, Indian Institute of Science
Evaluation Methods: 

To make evaluation possible, the students were given the full set of orbitals printed on three A4 size sheets and asked to match all of them.

Depending on the number of correct matches, the correct identification and correct shading, they were given points.

Alternatively, they were asked to do it at their leisure.

Evaluation Results: 

There is no direct evaluation of the student at the end of this exercise. But the bright smiles on their faces after they find a perfect match suggests that they understand it better than before!

Description: 

Students are often presented with the finished MO correlation diagrams of molecules like bis benzene chromium or ferrocene in classes and in organometallic chemistry text books. This activity helps them match the ligand group orbitals of the two benzene rings with the metal valence orbitals. Their understanding and appreciation of such diagrams is significantly enhanced when they find out how only some matches have the appropriate symmetry requirements.

Learning Goals: 

1. A student should gain better appreciation of the molecular orbitals formed by interacting orbitals on the benzene ring and the valence orbitals of the metal . 

2. A student should understand the difference between sigma, pi and delta type interactions. 

3. Help the student understand why only a few orbitals on the benzene ring and the valence orbitals of the metal can interact.

Equipment needs: 

Print outs of the ligand group orbitals and the metal valence orbitals on as thin a paper as possible. 

A pair of scissors.

 

Prerequisites: 
Course Level: 
Implementation Notes: 
•Large sized ligand group orbitals (LGO) and the valence orbitals of the metal were separately printed out on A4 sheets. 1 per A4 sheet.
 
•The printed orbitals were folded put into a basket. 17 sheets (8 ligand group orbitals and 9 metal orbitlas) are available.
 
•Each student was asked to pick one sheet. (If there are more than 17 students, students can be asked to pair up.)
 
•If less no. of students are there, a few pairs can be used for the demonstration and not distributed to the class for matching! Or some students could match more than one orbitall!
 
•The coordinate system to be used was indicated on the board.
•The metal orbitals were not shaded. So the students marked + (plus) and – (minus) on the lobes.
•One LGO was held up against a source of light and it was matched with metal orbitals till the correct match was identified.
•The molecular orbital was identified as σ, π, or δ, type interactions.
•The correct lobes on the metal orbital was shaded to match the lobes of the ligand group orbital.
 
It the sheet is semitransparent, it can be held against the light to see the match!

 

Time Required: 
The activity can take close to 30 minutes from start to finish

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