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Q2: Week 6  – 12/20 – 12/23

                                                                                                                                                                                         Jump toTuesday,   Wednesday,  Thursday, Friday                                                                                                                      ______________________________________________________________

12/20 – Monday – A Day – A Day – 2/3a Lab, 4 

Main focus –                                                                                                                                                         
                                                  

     a) To Review the concept of Crystal Field Theory

    b) To Review Spectrophotometry

    c) To begin Lab 16 – % copper in brass

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: 4 Ag  +  2H2S  +  02  —>  2 Ag2+  2 H20
                                                                                                                              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?

Period 2/3:  

1. Demo Review/ Nitric acid copper demo:

2. Crystal Field Theory and Spectrophotometry Review

3.  Lab 16 begins – 

      a) dissolve 2 brass shot with nitric acid.

      b) Make serial dilutions

Period 4: 

1. Demo Review/ Nitric acid copper demo:

2. Crystal Field Theory and Spectrophotometry Review

 

Notes For the Crystal Field Theory:                                                                                                            

Crystal Field Theory – Explanation of colored solutions from transitional metal complexes 
         
 
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 ? 
                                                                                                                  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.

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 – Fe+2 solution reacts to Fe+3 with oxygen in flask.  Why is it getting cloudy?
                                                                                                                                                                                                      I have to make the  Fe+2  solution fresh each day. 
 
       3 hours later... (in a bad French accent)
 
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.
 

Spectrophotometry Presentation:

Crystal Field Theory Presentation:

End of week 5!

      ______________________

Lab 16 – The Percent by Mass of Copper in Brass.

               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 .40M solution), 
 
        b) Make our serial dilutions to calibrate the spectrophotometer
 
                     0.40 M (Standard),   0.02 M,  0.10M,  0.05M  of Cu(NO3)2
 
        c) 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.
 
         d) 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!
 
         e)  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.
 
          f) Determine solutions concentration (molarity) using the Beer’s Law graph that was made yesterday (by  
           using linear algebra).
 
          g) Calculate the moles of copper, grams of copper and finally the percent by mass of copper.
                                                                                                                                                                                  Lab 16 – Non-formal– Write-up requirements:  This lab will be a Slide-up

 

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 SlideIf needed
 
I will explain e) on Wednesday!                         

____________________

12/20 – Monday Homework: – 

                                                                                                                                                                                                                               
1:  Please complete the class worksheet with the lecture and or key. 
 
2006 B spectrophotometry question.pdf
View Download
 
2006 B spectrophotometry question key p.pdf
View Download
Spectrophometry and 2006 B worksheet review:
  • Start at 25:50 for the worksheet review. If you want more spectrophometry review please feel free to watch the entire video.

 

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12/21 – Tuesday  – B Day – 2, 3b/4 Lab 

Main focus –                                                                                                                                                         
                                                  

    a) To continue with the percent by mass of copper in brass lab

    b) To Review concepts of spectrophotometry and crystal field theory.

 Period 2: 

1.  Complete making the standard solutions from the serial dilution of 0.40 M CuSO4
2.  Calibrate the spectrophotometer and run the known sample to create a Beer’s Law Graph.
3.  Make the final solution  from the dissolved brass.
4. Calculate the percent by mass of copper in the brass sample.                                                                                                                                                                                                                                                                                                                                        
Period 3/4: 
1. Complete the Lab 16
                                                                                                                                                                      

      ______________________

Lab 16 – The Percent by Mass of Copper in Brass.

               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 .40M solution), 
 
        b) Make our serial dilutions to calibrate the spectrophotometer
 
                     0.40 M (Standard),   0.02 M,  0.10M,  0.05M  of Cu(NO3)2
 
        c) 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.
 
         d) 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!
 
         e)  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.
 
          f) Determine solutions concentration (molarity) using the Beer’s Law graph that was made yesterday (by  
           using linear algebra).
 
          g) Calculate the moles of copper, grams of copper and finally the percent by mass of copper.
                                                                                                                                                                                  Lab 16 – Non-formal– Write-up requirements:  This lab will be a Slide-up

 

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 SlideIf needed
 
I will explain e) on Wednesday!                         

____________________

12/21 – Tuesday Homework: –                                                                                                                                                                                                                           

1. Study redox titrations and spectrophotometry labs – Test tomorrow on both labs.
     OH and I will be collecting something tomorrow. 
 
2. Begin the slide-up of Lab 16 using the shared link to the google presentation.   The more you understand this lab the more better you will do tomorrow.  DUE Tomorrow!  You can skip the Background. I really just want to see the calculations and your graph!
 
IF you need help with the calculations please use the video posted below:                                                                                                                                                                                                                                                                                                                            

Lab 16 Review of the calculations:                                                                                                                     

 

______________________________________________________________________________________________________________________

12/22 – Wednesday – A Day – A Day – 2/3a Lab, 4 

Main focus –                                                                                                                                                         
                                                  

    a) To take the Redox volumetric titration and Spectrophotometry test.

    b) To introduce the cross – linked polymer synthesis lab.

    c) To accept many holiday gifts from very appreciative students.

Period 2/3:  

1.  Redox volumetric Test

2.  Cross Linked Polymer Synthesis activity introduction

Period 4: 

1.  Redox volumetric Test                                                                                                                                                                       

 

______________________

The Synthesis of a Cross Linked Polymer

               This lab might be a stretch for us right now but I hope it sticks to you.

        a) Dissolve 4 grams of polyvinyl chloride in 100 ml of distilled water. Make sure to keep the warm                   solution at or near 70 degrees Celsius.  If too warm it will denature and curl up.
 
        b) In a plastic cup please add 16 ml of sodium tetraborate with your choice of food coloring, glitter,               and/or fluorescent compound (if you want to have it glow in the dark).
 
        c)  Once the polyvinyl chloride is dissolved, POUR the hot polyvinyl solution into the plastic cup                     with the sodium tetraborate, food coloring etc and stir with wooden popsicle stick like a banshie!  
 
         d) Once the polymer cools enough we will test its physical properties and then dispose of it in a  ziplock baggie.
         
       

______________________

12/22 – Wednesday Homework: – 

                                                                                                                                                                                                                               
1. Shop and wrap presents for the special tall teacher. My size is very tall, boys husky

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12/23 – Thursday – A Day – B Day – 2, 3b/4 Lab 

Main focus –                                                                                                                                                         
                                                  

    a) To bring in heavy presents for your tallest teacher.

    b) To calculate a in A = abc

    c) To synthesize a cross – linked polymer.           

Period 2:  

1.  Cross linked Polymers!

 

Period 4: 

1.  review of Test and constant a of A = abc

2. Cross linked Polymer!

                                                                                                          

______________________

The Synthesis of a Cross Linked Polymer

               This lab might be a stretch for us right now but I hope it sticks to you.

        a) Dissolve 4 grams of polyvinyl chloride in 100 ml of distilled water. Make sure to keep the warm                   solution at or near 70 degrees Celsius.  If too warm it will denature and curl up.
 
        b) In a plastic cup please add 16 ml of sodium tetraborate with your choice of food coloring, glitter,               and/or fluorescent compound (if you want to have it glow in the dark).
 
        c)  Once the polyvinyl chloride is dissolved, POUR the hot polyvinyl solution into the plastic cup                     with the sodium tetraborate, food coloring etc and stir with wooden popsicle stick like a banshie!  
 
         d) Once the polymer cools enough we will test its physical properties and then dispose of it in a  ziplock baggie.
         
       

Form______________________

12/23 – Holiday Homework: – 

                                                                                                                                                                                                                               

1. Please respond to the Holiday Form daily over break by writing the time left in your break with the countdown below.


                                                                                                                                                                                                 
 
1: Holiday Form:

 

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12/24 – Friday – Christmas Eve OFF  – Holiday Break!

                                                                         Happy New Year!