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Archive – Q2  week 5 – 19-20

Week of 12/2 – 12/6  – 
12/3 – Monday – period 2 –  
 
1. quick review of last weeks redox worksheets.
 
Redox 4 – Net potentials Demonstrations worksheet 1213 key p.pdf
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Redox – Activity Series net potentials KEY.pdf
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From this year’s August Chemistry Regents:
2)  Nitric Acid / Copper Demo vs the penny demo:
 
Take out your reduction potential table and you can see that HCl does not spontaneously react with copper, however it does with HNO3 because the nitrate ion is a better oxidizing agent.  
 

 

 
3: Silver plate non tarnish demo:
 
There are 2 reactions in this reaction that removes the tarnish (rust) from the oxidation effect of sulfur in our air that usually results from the breakdown of organic matter (dead animals and plants).
 
Silver exposed to Air that has hydrogen sulfide:  2 Ag(s) + H2S(g) —> Ag2S(s) + H2(g)
                                                                                                                      tarnish
 

#1                        3 Ag2S(s) + 2 Al(s)+ 3 H2O(l) —> 6 Ag(s) + Al2O3(s) + 3 H2S(aq)

 
 
#2                         3 NaHCO3(aq) + 3 H2S(aq) —-> 3 NaHS(aq) + 3 H2O(l) + 3 CO2(g)
 
 
What type of reactions are these?
 
 
4: Underwater fireworks:
 
#1                2KMnO4 (s)  +  16HCl  —> 2 KCl   +  2MnCl2 (aq)  +  8 H2O (l)  +  5Cl2 (g)
 
#2                              CaC2   +   2H2O  —>  C2H2   +   Ca(OH)2
 
#3                              C2H2   +    Cl  —>   2HCl  +   2C   +   heat (light)
 
From Today’s 4th period class:
 

Underwater Firework demo explained:

 
From this year’s August Chemistry Regents:
                                 period 3/4
1. complete redox discussion with demonstrating acid and water demos with metals.
    
nitric acid demo and balance on worksheet.
 
Redox 4 – Net potentials Demonstrations worksheet 1213.pdf
View Download
 
Redox 4 – Net potentials Demonstrations worksheet 1213.pdf
View Download
 
2. Redox demos- 
 
3. Lab 13 complete review and completion.
 
12/2 – Monday Homework:
1:  Please complete the class worksheet with the lecture and or key.
 
2006 B spectrophotometry question.pdf
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2006 B spectrophotometry question key p.pdf
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End of Monday!

12/3 – Tuesday – period 2/3  
 
1. Lab 13 complete review and completion.
 
2.  Crystal Field Theory – Explanation of colored solutions from transitional metal complexes
 
Crystal Field theory:
 
 
Why was the Cu+2 ion that was produced by the oxidation of the nitrate ion in the nitric acid that was added to the copper in the demo yesterday produce a blue-green color?
 
Why does our blood which contains iron (Fe+3)  have a maroon color?
 
Why did the permanganate ion (MnO4-1) have a purple color in our Volumetric Redox Titration Lab (lab 13)? Remember in the permanganate ion there is a Mn+7 ion.
 
Why are plants mostly green because the main photosynthetic pigment pigment in chloroplasts chlorophyll absorbs the blue and red part of the visible spectrum.  This is part of the negative theory of light (which I will review in a later date).
 

Gavin Acuri 2019

   This is an absorption spectrum from the pigments that were extracted from our Spinach Plants last year.

Notice the these combined pigments in the thylakoid membranes of chloroplasts ABSORB visible light in the Blue and Red parts of the visible spectrum and thus Green is transmitted back to our eyes.

The negative theory of light work with inks and paints.
Green paint is the result of the chemicals in the paint absorbing the red and blue parts of the spectrum due to their electron arrangements around the atoms in the molecules.

Plants appear green because they are receiving green photons ( so that they can transmit them back to you).
 
What do plants look like when they do not get green photons?
 
The spectrophotometer above directs a full spectrum of white light at its target and measures what is missing.
 
Now Chlorophyll, a molecular compound, does not contain a transitional metal and it creates colors by a different theory that we will learn later in the year (pi – stacking). 
 
So what is special about transitional metals that create colored solutions?

 Transitional metals have properties that will lead to them absorbing parts of the visible light spectrum which results when their cations form complex ions.

 1.  They are smaller atoms as they are “transitioning” into nonmetals.  They are positioned to the right of the Group 1 (Alkali Metals) and Group 2 (Alkaline Earth metals) and thus have more protons than the more reactive metals.

 2.  They have multiple oxidation states with some of those oxidation states having large positive values (ex. Mn+7 in the permanganate ion).

 3.  They have d orbitals that are not completely filled with electrons that allow for electron transitions. It is these d orbitals that get “split” into 2  distinct energy levels that allow for the the absorption of parts of the visible spectrum that produces the color we see in solutions.

           [Cu(H2O)6 ]+2
Let us consider another demo (that I cannot do in class anymore) called Vesuvius Fire.
                                                          -3          +6                             +3                         0
                                                      (NH4)2Cr2O7 (s) → Cr2O3 (s) + N2 (g) + 4 H2O (g)
We can see the color change is due to the Cr+6  changing to Cr+3 in the redox demo above.
 
So colors form transitional metal ions in water come from theses complex ions due to the very large Electrostatic Force (Coulombs Law) that draws the oxygen end of water (ligand) into the d orbitals of the metal ions. If the oxygen end is drawn directly into the d orbital it will destabilize (increase in energy) of those orbitals.  If the Oxygen end goes in between the d orbitals it does not increase the energy of the those electrons as much and thus the d orbitals which are normally the same energy are now split into 2 different energy levels.
 

Crystal field theory – explaining the color of transitional metal ions in solution.
 
       3 hours later... (in a bad French accent)
Crystal Field Theory:

Crystal Field Theory

 
     
Spectrophotometry:
3: Lab 14 – The Determination of percent by mass of NICE copper in Brass
                   
        a) Make our serial dilutions to calibrate the spectrophotometer
 
                0.40 M,   0.02 M,  0.10M,  0.05M  of Cu(NO3)2
       
        b) measure the absorbance of our standard solutions
                        
        c) Make a best fit (regression line) and print.
 
                                period 3
 
1. Crystal field theory/Spectrophotometry – use note above
12/3 – Tuesday homework
 
 
1. Please complete the AP free response question below (no Grodski changes!) and review with the key below.
                      
 
Spectrophotometry AP question 2 – 2003-1.pdf
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Spectrophotometry AP question 2 – 2003 AP Key.pdf
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End of Tuesday

12/4 – Wednesday – period 2 –  
 
Connections:
In Lab 13 – Volumetric REDOX Titrations – We used Fe+2 ions to Standardize the KMnOsolution.
The MnO4  solution  oxidized the Fe+2  into Fe+3 .  The Fe+2  reduced the The MnO4  solution to turn from purple (Mn+7 form) to colorless (Mn+2).  
 
IF the the Fe+2  solution sits in volumetric flask it slowly changes into Fe+3 as oxygen in the flask and in the solution oxidizes the the Fe+2 solution. Notice the development of color in the 24 hour period.  
 
 I have to make the  Fe+2  solution fresh each day.  Why is there a color developing?

 

As the Fe+2  becomes  Fe+3  the solution has a greater ability to absorb wavelengths of visible light because Fe+3 makes a complex ion with water that attracts water with such high Coulombic attractions that the water’s lone pair of electrons are pushed into the iron’s (Fe) d – orbitals directly interfering with some d – orbitals and not others based on their orientation in space.  The orbitals that “feel” the oxygens electrons become destabilized (increase in energy) and there is a spit in the energy level between these orbitals that were initially the same energy.
 
This splitting of d orbital energy levels provides a pathway for electrons to transition to higher energy levels when low energy visible light energy (photons) are absorbed.  Not all of the wavelengths of light are absorbed thus the ones that are not absorbed are what we see.
The spectrophotometer picks up the transmittance (which is the what is absorbed or missing from our eye.)
A photon of light of a certain wavelength is absorbed by electrons in lower energy d orbitals that can now transition into higher energy d orbitals (that split due to electrons being pulled directly into the orbitals). The absorbed photon is now missing from the entire spectrum of light that is illuminating the complex and the color shown is what is left.
1. Quick review of spectrophotometry and past 2 nights homework.
 
2. Complete Lab 14 – a percent by mass lab – need initial mass at the beginning!
 
        a) Set up your spectrophotometer so that it is calibrated (to water in a cuvette), set to measure  
             a peak wavelength (with the .4M solution) , and ready to graph Absorbance with KNOWN  
             concentrations made from the serial dilutions.
 
        b) Place your four cuvettes of KNOWN concentrations into the spectrophotometer from  
              lowest concentration to highest and type in your concentrations (with Keep button like you  
              did with the Acid /Base titrations.  This is called a Beer’s Law graph. Hit the regression  
              button to make a line of best fit that will also provide the slope and y – intercept data.
              Print this Graph.
 
         c) Dilute the dissolved brass solution (from nitric acid that was added to your brass samples yesterday). You  
             will dilute to 100.0 using a 100.0 ml volumetric flask. Googles and gloves here!
 
         d)  Once diluted to a the known volume, 100.0 ml, all you need to know to determine the percent of copper in  
               the brass sample was obtain it concentration.  You will now fill a an empty cuvette with this solution.            
               Place it into the spectrophotometer and determine its Absorbance.
 
          e) Determine solutions concentration (molarity) using the Beer’s Law graph that was made yesterday (by  
           using  linear algebra).
 
           f) Calculate the moles of copper, grams of copper and finally the percent by mass of copper.
                                        period 3/4- 
 
1. Complete our discussion of crystal field theory – 
 
            a) electron transitions – Zn vs Cu
            b) Demo, video of dichromate- crystals redox
            c) Spectrophotometry presentation:  Transmission vs. Absorbance
 
2.  Lab Notes
3.  Run the Lab
12/4 – Wednesday – Homework:   
1.  Start the Volumetric Titration Quiz – Take Home – Due Friday
Volumetric Titration Quiz.pdf
View Download
2.  Start the informal lab write-up of Lab 14. This will be a slide- up. I will share a Google Slide Blank        presentation with you to complete individually.
 
You need to at least complete the calculations and determine the percent
       by mass of copper in the brass.
 
I have posted a video below to help if needed.
Please follow the lab requirements below. It is an informal lab (SLIDE – UP) but you will lose points if you are missing the listed components below. 
 
*Gavin’s group had an issue with a spectrophotometer.  I reran your cuvettes you made with a new spectrophotometer. The file below is a screenshot of the Beer’s Law graph. In the Lower left corner you will see an absorbance reading and THIS VALUE IS THE VALUE OF THE TEST CUVETTE that was obtained by oxidizing the brass shot with nitric acid.
 
Gavins and Conor Lab 14 Data.png
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All Groups:
 
Lab 14 – Cole, Alex, and Rose.png
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Lab 14 – Ellie, Amanda, Debra.png
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Lab 14 – James.png
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Lab 14 – JAMS.png
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Lab 14 – Jaqueline, Emily, Ryan.png
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Lab 14 – Joey and Brandon.png
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Lab 14 – Josie, Lola, Maddie, Val! .png
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Lab 14 – Quinny and Gianna.png
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Lecture on how to complete the percent copper in brass Lab:
You need to understand this in order to complete the Take Home Quiz.
 
 

 Informal Lab write – up requirements for Lab 14:

 
1. Title Slide –  Title of Lab / name / date
 
2.  Background SLIDE– How spectrophotometry works/Notes
3. Objective SLIDE:
 
4. DATA SLIDES:
 
    a) Balance reaction between brass (copper only) and nitric acid (HNO3 ) on Data page
 
                                                                     NO3-1   —–>  NO2
                                                                         Cu   ——-> Cu+2
    b) Data table:
 
                a) mass of Brass Shot total
                b) balance nitric acid/calculation
                c) Serial dilution calculations
 
                
    c) Beer’s Law Graph on its own SLIDE  I will post digital copies of each lab
 
    d) final calculation of % by mass of copper in shot – Show all calculations
 
    e) Calculate the absorptivity constant (a) using the absorbance (A) and concentrations (c).
 
                    A = a b c
 
                         Using the absorbance values from the spectrophotometer (A), the path length ( b = 1 cm ), and the 
                         concentrations of these solutions (c) solve for a with the correct units.  Make a chart. These  
                        values that you calculate should be similar as it is a constant.
 
 5Error analysis SLIDE:   The limitation of the lab was based on how well you made the solutions and if the absortivity constant STAYED CONTANT!  I will explain once you finish step e.
 
 
6. Sources Slide: If needed
End of Wednesday…

12/5 – Thursday – period 2/3  
 
1.  Complete and Review Lab 14 spectrophotometry and lab write-up requirements
 
2.  Discuss the observation of diluting the concentrated Cu solution in the evaporating dish.
 

Connections:
In how many reactions that we witnessed or discussed in class up to this point did we generate a gas?
Did we generate a gas in electrolytic cells?  Did we split water using an electrolytic cell?
I did this demo in class.
 

Could we use the volumes measured gas generating reactions to do stoichiometry?  

            
            1. determine the limiting reagent
            2. Determine the amount of the reagents ( amount of active ingredients, % by mass )
            3. Determine the empirical formula? (mole ratios of atoms)
            4. identify the compound (molecular mass)
            5. Determine the Amperage needed to power this non-spontaneous reaction?
 
What does the amount of the gases generated above tell use about the chemical formula of water?
 
I conveniently dismissed the amount of gas generated in all of our reactions till NOW!  What labs did we do that generated gases that we could used for stoichiometry?
 
How about the last one?
 
Lab 14 oxidation of Cu and Zinc in brass:

 

Could we have measured the amount of NO2 gas collected and through stoichiometry determined the amount of copper in the brass, skipping the spectrophotometer entirely?
 
 
3. Gas Laws begin– measuring gas pressure all started with the story of Torricelli
 
                        He developed the concept of manometer to solve the problem of the water well in Tuscany Italy.
                            
A water well that brought water to the city state of Tuscany was recently moved inside the city walls, which had a higher elevation than where it once stood.  The well’s hand crank could not deliver any water when it was in the cities walls but worked outside the city states wall.
 
                   By solving this problem he developed the first way to measure and quantify pressure.
 
Pressure intro Presentation: Torricelli – discovered and used first manometer!
(we started at on slide 27..we were not crazy and did not start in order!)

Pressure intro

Period 2 lecture – Story of Torricelli – Manometers introduction with worksheet: 
For those who are missing a college class to visit colleges.
Period 4 students should watch the beginning of the this lecture as I explain the connections of what we have been doing into Gas Laws.
 
 
                     
    A) Classwork:
 
Gas Law worksheet 1 – Manometers.pdf
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Gas Law worksheet 1 key – manometers.pdf
View Download 
    B) Static vs. Dynamic Gas Law Derivations-  first of many!
 
A) the Ideal Gas Law formula:    PV = nRT 
       (Static Gas Law formula
 
        B) the Combined Gas Law formula:      P1V1     =     P2V2
                    (Dynamic Gas Law formula                          _____                            _____
                                                                                                             T1                    T2
               
Presentation with animations that I used to explain the variables that affect gases:

Gas Law Derivation

 
                 
                                   period 4 :
 
1.  Complete and Review Lab 14 spectrophotometry and lab write-up requirements
 
2.  Discuss the observation of diluting the concentrated Cu solution in the evaporating dish.
       see image posted above:
 
Connections:  see above.
 
3. Static vs. Dynamic – Derivation  – 
 
This is the gas law derivation that I did in class:
For those missing a college class to visit a college class.
The story of Torricelli and manometers will be tomorrow!
12/5 – Thursday – Homework – Lab 14 – Slide-up due Monday!
 
Period 2/3 students :  Complete 1, 2, 3 below
 
Period 4 students: Complete 2,3 below
 
1.  Complete the word problems in the manometer worksheet.  
      The lecture below will help you work through the word problems.  
      Please try to see that these are really manometer problems.
      You can also use the key below to review these problems.

Manometer worksheet that review the word problems:

 
Gas Law worksheet 1 – Manometers.pdf
View Download 
Gas Law worksheet 1 key – manometers.pdf
View Download 
2.  a) . Please watch the last few minutes (from 13:50 on) of the gas law derivation posted below
            (In both classes I did not quite finish it with Combined Gas law formula.)
 
       b) Complete Gas Law worksheet 2.pdf and review with the key.
             – now you are applying the 2 gas law equations, Do I use the dynamic or static? 
    
Gas Law worksheet 2.pdf
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Gas Law worksheet 2 key.pdf

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3. complete the Gas Law worksheet 4 worksheet and review with the key or lecture below.
Gas Law worksheet 4 – honors chem.pdf
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Gas Law worksheet 4 key – honors chem.pdf
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Derivation of Ideal Gas Law / combined gas law – Formula review lecture:
Lecture that reviews Gas Law worksheet 4. pdf:
End of Thursday!

12/6 – Friday – period 2 
 
1.  Story of Torricelli  reviewed- manometers to units of Pressure and factors that affect Pressure
    a) Manometers – The first pressure device – Units  of pressure – the square demo – 
 
         – used beginning of Pressure presentation for the units
 
2. Derivation review – 
    
    a) Static vs. Dynamic – Derivation review
 
        – R slope/units
 
        – Relationships only work when you keep the other variable constant – 
 
        – Destroy Boyles Law with liquid nitrogen-
 
 – Last night’s Homework review – When to use Dynamic or Static
 
        Question 4 – of Gas Law worksheet 2.pdf
 
3. New Derivation of Density and Molecular Mass of a Gas
 
4. Glass with water/cardboard, Glass with water/without cardboard!, Large Flask and Cardboard
5. Bourdon gauges/manometers – connections – 
 

Animations for gas law derivations:

Gas Law Derivation

 
                          – period 3/4
 
1. Complete Note-taking of gas law derivations:
 
        a) Graph of Boyles Law discussion      
        b) R is a slope
 

2.  Story of Torricelli –    manometers to units of Pressure and factors that affect Pressure

a) Manometers – The first pressure device – Units   
b) Static vs. Dynamic – Derivation review – 
 
        a) Density and Molecular Mass formula derivation
 
3. Bourdon gauges/manometers – connection
 
Pressure intro Presentation:

Pressure intro

 
Today’s Lecture: Story of Torricelli  (not from this year)- 
Manometer demonstration:
 
12/7 – Friday – Homework: – Quiz Monday on Derivations… 
                                                                Also collecting one of Homework worksheets Monday..
                                                                             Lab 14 – Slide-up due Monday
 
Period 3/4 Students will complete everything below:
Period 2 students will complete everything AFTER #1 .
 
1.  Complete the word problems in the manometer worksheet.  
      The lecture below will help you work through the word problems.  
      Please try to see that these are really manometer problems.
      You can also use the key below to review these problems.

Manometer worksheet that review the word problems:

 
Gas Law worksheet 1 – Manometers.pdf
View Download 
Gas Law worksheet 1 key – manometers.pdf
View Download 
2. Please complete following worksheet and review with the key.
 
This might be collected Monday!
 
You may wonder why we are doing this worksheet now.  It will makes sense when you complete it
Intro Electrolytic Cells worksheet 3.pdf
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Intro Electrolytic Cells worksheet 3 key p.pdf
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3. Watch the 

Derivation of Molecular Mass / density gas law formula Lecture below and complete the worksheet below:  WE did derive this in class!
                                                                                                               
4. Complete the Gas Law Stoichiometry Density 2009 worksheet below and review with the key below.
      This might be collected Monday!
 
Gas Law Stiochiometry Density – 2009.pdf
 
Gas Law Stiochiometry Density – 2009 AP Key.pdf
View Download
 
Hmm…we may now be ready to start some gas law labs!!!
 
5.  Study for a Derivation Quiz Monday – 
      You will asked to derive:
 
        A) the Ideal Gas Law formula:    PV = nRT 
        
        B) the Combined Gas Law formula:      P1V1     =     P2V2
                                                                                                           _____                            _____
                                                                                                             T1                    T2
                
        
        C) The Molecular Mass formula:                       M = dRT
                                                                                                           P
 
 
        D) The density formula (from the above formula)   d = (solve from above)
 
Here is the quiz:
Gas Law Equations Derivation Quiz.pdf
View Download
 
Derivation of Ideal Gas Law / combined gas law – Formula review lecture:

END OF WEEK 5!