Select Page

Archive – Q2 week 5 – 20 – 21

Week of 12/14 – 12/18 – Please Refresh every time you open– this page is changing often!

 

The 4 day – A, B, C, D cycle looks like this:
                                                       Day                               Period
                                                                           2                       3                       4       
                
                                   In class:         A               Lab                   Lab               Single Class
                                   Remote:                           Lab                   Lab              Single Class
 
                                         In class:         B         Single Class        LAB                   LAB
                                                          Remote:                     Single Class        LAB                   LAB
 
                                        In class:              C         Single Class              LAB                    LAB
                                   Remote:                     Single Class        LAB                    LAB
 
        Monday                 In class:          D               Lab                   Lab             Single Class
                                   Remote:                           Lab                   Lab              Single Class
                 
 
This weeks 5 day Schedule:
 
12/14  -Monday – “D” Day – period 2,3 (Lab)  –  I   2(B,D) 3(D) AP CHEMISTRY
                                                    – period 2,3 (Lab) –  R  2(B,D) 3(D) REMOTE INSTRUCTION
  
                                                     -period 4 – I  3(B) 4(B,D) AP CHEMISTRY
                                                     -period 4 – R 3(B) 4(B,D) REMOTE INSTRUCTION
 
12/15  – Tuesday “A” Day – period 2,3 (Lab) –     2(A,C) 3(A)  AP CHEMISTRY
                                                     –period 2,3 (Lab) –  R   2(A,C) 3(A) REMOTE INSTRUCTION
                                                      -period 4 – I   3(C) 4(A,C) AP CHEMISTRY 
                                                      -period 4 – R  3(C) 4(A,C) REMOTE INSTRUCTION
12/16  – Wednesday  “B” Day  period 2,  –  I   2(B,D) 3(D) AP CHEMISTRY
                                                      – period 2, –  R   2(B,D) 3(D) REMOTE INSTRUCTION
 
                                                        -period 3,4 (LAB) – I   3(B) 4(B,D) AP CHEMISTRY
                                                        -period 3,4 (LAB) – R  3(B) 4(B,D) REMOTE INSTRUCTION
 
12/17  –  Thursday –  “C” Day – period 2, –  I    2(A,C) 3(A)  AP CHEMISTRY
                                                          –period 2, –  R   2(A,C) 3(A) REMOTE INSTRUCTION
                
                                                      -period 3,4 (LAB) – I.  3(C) 4(A,C) AP CHEMISTRY 
                                                      -period 3,4 (LAB) – R  3(C) 4(A,C) REMOTE INSTRUCTION
 
12/18  – Friday-  “D” Day – period 2,3 (Lab)  –  I   2(B,D) 3(D) AP CHEMISTRY
                                                  – period 2,3 (Lab) –  R  2(B,D) 3(D) REMOTE INSTRUCTION
  
                                                      -period 4 – I  3(B) 4(B,D) AP CHEMISTRY
                                                      -period 4 – R 3(B) 4(B,D) REMOTE INSTRUCTION

12/14  -Monday – “D” Day – period 2,3 (Lab)  –  I   2(B,D) 3(D) AP CHEMISTRY
                                                    – period 2,3 (Lab) –  R  2(B,D) 3(D) REMOTE INSTRUCTION
  
                                                     -period 4 – I  3(B) 4(B,D) AP CHEMISTRY
                                                     -period 4 – R 3(B) 4(B,D) REMOTE INSTRUCTION
The Blue team and the Orange team are Remote today.  Please move to the remote instruction page.
Period 2,3 – 
 
Some might need to redo Part 1 – you have the time today to do so if needed.
 
Perform the Aspirin Lab Part 2.
 
    a) Make the HCl solution needed to back titrate 
 
    b) crush the aspirin tab(s)
    c) Add distilled water and heat solution for 10 minutes.
    d) Add your base solution (in excess).
    e) stir using the stirring bar and the magnetic stirrer for a few minutes. Solution should still be warm.
    f) Back titrate with HCl solution. Make sure you rinse the buret with HCl as it had a base in it previously!
 
    e) calculate the milligrams of aspirin in your tabs!
 
Period 4- Recorded lesson that will be posted later.
 
1.  Lets continue our discussion with more Redox reactions that require acidic or basic conditions.
 
Lets remember that oxidizing agent or the oxidizer is a chemical that drives others chemical into oxidizing (losing electrons).
    
                         The oxidizing agent gets reduced gains electrons as it forces other chemicals to lose electrons.
                                                           
 
Strong Oxidizers or oxidizing agents are easily identified by their arrangement of electron sinks.  Usually a group of very electronegative oxygens surrounded by a highly charged positive ion (that is small) . Due to Coulomb’s law, these chemical force chemicals to lose electrons and and can be very dangerous.
 
Examples: KMnO, KCr2O7 , H2O2 , KNO3, NH4ClO4
I have included some of these strong oxidizers into the Standard net potential table that I gave you earlier this year.
Table T with Net potential table 1718.pdf
The proton that is dissociated from acids is heat sinking missile for the loosely held electrons of metal and it causes the oxidation (loss of electron) of the metal and thus H+ is the oxidizing agent.  It however it not strong enough to pull electrons from all metals.
 
The standard cell experiment that helped us determine the voltages of the half reactions in the Standard Reduction Table uses the proton (H+) as the oxidizer to force the other chemical  reduce BUT it is not strong enough to make all chemical oxidize and thus explains why there is change in the signs in the standard reduction table around the reaction with protons (H+):
 

Notice the that 2 protons oxidize other chemicals and thus gain 2 electrons to produce hydrogen gas.

Notice that all half reactions below it have negative standard potentials because these half reactions are MORE spontaneous in the Reverse Reaction thus they are better at getting oxidized, which means the proton is ONLY a strong enough oxidizing agent to those chemicals (metals) on the right and below the standard cell half reaction.

This means acids that only produce protons can only produce hydrogen gas with those metals reactive enough (below it ).  

Example:  HCl can produce hydrogen gas with Pb  (E0cell = 0.13) but not with Cu (E0cell =  0.34)

 

New York State uses Table J instead of a “real Net potential table’!
 
  
So copper is not reactive in acids?? Well its not reactive with protons BUT it will reactive with its conjugate base that is actually a oxidizing agent!
 
Today’s lesson:
 
12/14  -Monday – “D” Day Homework:
 
1. Please complete the following released AP problem with we using the video below:
Stiochoimetry 7 – 2010B 1819.pdf
View Download
 
An older key but it will do the trick:
Stiochoimetry 7 – 2010B AP Key p.pdf
View Download
Stiochoimetry 7 – 2010B.pdf video:
 

 

End of Monday..

12/15  – Tuesday “A” Day – period 2,3 (Lab) –     2(A,C) 3(A)  AP CHEMISTRY
                                                    –period 2,3 (Lab) –  R   2(A,C) 3(A) REMOTE INSTRUCTION
                                                   -period 4 – I   3(C) 4(A,C) AP CHEMISTRY 
                                                   -period 4 – R  3(C) 4(A,C) REMOTE INSTRUCTION
 
The RED team and the Green Team are remote today. Please move to the Remote Instruction Page.
Period 2, Period 4 – Class lesson.
 
1.  Net potentials and Table J worksheet – 
 
Table T with Net potential table 1718.pdf
 
        a) determining spontaneity with and without voltages
 
Redox – Activity Series net potentials.pdf
View Download
Redox – Activity Series net potentials KEY.pdf
View Download
 
        b) Determining whether protons from acids will produce hydrogen
 
                HCl reactivity series lab
 
        c) penny demo vs. Nitric acid demo
 
        b) balance Nitric acid demo worksheet.
 
Redox 4 – Net potentials Demonstrations worksheet 1213.pdf
View Download
 
Redox 4 – Net potentials Demonstrations worksheet 1213 key p.pdf
View Download
From the last August Chemistry Regents:
Reactivity series Lab  – Acid added to metals (the action of acid is actually a redox reaction):
 
                               Metal(s)  +   2 HCl    =>    Metal Chloride (aq)  +  H2 (g)
 
                              Ex:    Mg (s)  +  HCl   =>  MgCl2 (aq)   +   H2 (g)
 
             NET ION:      Mg(s)  +     2H+   =>  Mg+2  +   H2 (g) 
 
The proton is heat sinking missile for the loosely held electrons of the metal and it cause the oxidation (loss of electron) of the metal and thus H+ is the oxidizing agent.  It however it not strong enough to pull electrons from all metals.
 
Penny Demo:
 
Using our understanding spontaneity we can hollow out a post 1981 penny.
 
The proton is heat sinking missile for the loosely held electrons of the metal and it cause the oxidation (loss of electron) of the metal and thus H+ is the oxidizing agent.  It however it not strong enough to pull electrons from all metals.
Period 3 – 
 
Lab 15 – Determination of concentration of Oxalic acid by volumetric redox titration.
 
Lab 15 – Titration of Oxalic acid.pdf
MnO4–    is a purple compound due to the Mn+7 ion and when it gets reduced (gains electrons by acting as a oxidizing agent) and Mn+2 is colorless.    This is significant as we can use the color change to reach an equivalence point IN TERMS of Electrons to end the redox titration.  That is when the purple persists from the titrant (MnO4– ) for at least 30 seconds all moles of the electrons from the oxalic acid have been transferred to the MnO4.
We are not using an acid base indicator!  We are using a property of metal ions that have high charges = crystal field theory.  Crystal field theory provides colors to metals that have high coulombic attractions. Metals that a have high enough charge to create this affect are transitional. 
 
                                                                            +7
                                                                MnO4–    ——>  Mn+2
                                                                             purple                      colorless
 
Because the KMnO4 is a very strong oxidizing agent (1.52 volts) we need to standardize it to know exactly what its concentration is BEFORE we titrate the oxalic acid.
 
Today’s lesson:

 

 
12/15  – Tuesday “A” Day Homework – 
 
Please complete the following worksheets that we started in class and review their keys:
 
Redox – Activity Series net potentials.pdf
View Download
 
Redox – Activity Series net potentials KEY.pdf
View Download
 
Redox 4 – Net potentials Demonstrations worksheet 1213.pdf
View Download
 
Redox 4 – Net potentials Demonstrations worksheet 1213 key p.pdf
View Download
 
End of Tuesday..

12/16  – Wednesday  “B” Day  period 2,  –  I   2(B,D) 3(D) AP CHEMISTRY
                                                          – period 2, –  R   2(B,D) 3(D) REMOTE INSTRUCTION
 
                                                          -period 3,4 (LAB) – I   3(B) 4(B,D) AP CHEMISTRY
                                                          -period 3,4 (LAB) – R  3(B) 4(B,D) REMOTE INSTRUCTION
 
The Blue team and the Orange Team are remote today. Please move to the Remote Instruction Page.
 
Period 2, Period 3
 
Lab 15 – Determination of concentration of Oxalic acid by volumetric redox titration.
 
Lab 15 – Titration of Oxalic acid.pdf
MnO4–    is a purple compound due to the Mn+7 ion and when it gets reduced (gains electrons by acting as a oxidizing agent) and Mn+2 is colorless.    This is significant as we can use the color change to reach an equivalence point IN TERMS of Electrons to end the redox titration.  That is when the purple persists from the titrant (MnO4– ) for at least 30 seconds all moles of the electrons from the oxalic acid have been transferred to the MnO4.
We are not using an acid base indicator!  We are using a property of metal ions that have high charges = crystal field theory.  Crystal field theory provides colors to metals that have high coulombic attractions. Metals that a have high enough charge to create this affect are transitional. 
 
                                                                            +7
                                                                MnO4–    ——>  Mn+2
                                                                             purple                      colorless
Because the KMnO4 is a very strong oxidizing agent (1.52 volts) we need to standardize it to know exactly what its concentration is BEFORE we titrate the oxalic acid.is a very strong oxidizing agent (1.52 volts) we need to standardize it to know exactly what its concentration is BEFORE we titrate the oxalic acid.
 
 
1. Standardize the KMnO4 solution (0.10 M) with a 10.0 ml of Fe+2 solution (0.100 M).
 
2. Determine the concentration of the Oxalic acid solution by titrating the solution with the standardized KMnO4 solution.
 
Period 4:
 
1. Complete lab 15.
 
2. Nitric acid Demo – Balancing in Demo worksheet.
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   +    Cl2   —>   2HCl  +   2C   +   heat (light)
 
From Today’s 4th period class:
 

Underwater Firework demo explained:

 
12/16  – Wednesday  “B” Day  – Homework – 
 
1.  Please complete the Lab 15 (informal lab on the worksheet that I gave out).
     The following teams have gathered data in class:
 
        Blue TeamRed Team, and the Green Team.
        The Orange team will complete the lab tomorrow.
 
2.  Please complete the following question (3) from the 2018 AP Chemistry test using a separate piece of paper. Do  
     not try to complete the questions in between the questions. The answers to these questions on the test were          
    written on a blank essay book.
     
     Please skip the first 2 questions 3(a) and (b) as we have not learned these concepts in class yet.
 
     Please review your work with the Grodski Solutions and or the College Board Key.
        
2018 Free Response question 3.pdf
View Download
 
2018 Free Response question 3 Grodski Solutions.pdf
View Download
 
2018 Free Response College Board Key – question 3.pdf
View Download
 
End of Wednesday..

12/17  –  Thursday –  “C” Day – SNOW DAY!

 
12/18  – Friday-  “D” Day – period 2,3 (Lab)  –  I   2(B,D) 3(D) AP CHEMISTRY
                                                  – period 2,3 (Lab) –  R  2(B,D) 3(D) REMOTE INSTRUCTION
  
                                                      -period 4 – I  3(B) 4(B,D) AP CHEMISTRY
                                                      -period 4 – R 3(B) 4(B,D) REMOTE INSTRUCTION
The Blue Team and the Orange Team are remote again today. Please move to the remote instruction page.
 
Period 2,3:
 
1.  Advanced Redox Reactions/Demos – 
 
        a) Penny Demo – nitrate ion as the oxidizing agent.
        b) Un- tarnishing silver – Redox, precipitation, acid/base
        c) Underwater fireworks – redox/ acid base
 
Period 4
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)]+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:
Today’s Crystal field Theory AND spectrophotometry Lecture:
 
12/18  – Friday-  “D” Day Homework- Lab 15 – Due on your next in class date
 
1. For those that did not see my lecture today on crystal field theory (why transitional metals make colored  
    solutions) please view today’s lecture posted above.  
 
2. Please complete the AP free response question below (no Grodski changes!) and review with the key below.  You will need to view my tutorial video to follow along with me using the worksheet below to completely understand the spectrophotometry procedure. 
Can you guess what your next lab will include?
 
3. Complete the form below.
 
 
4.  The Orange Team will have to complete the Lab 15 – Redox Titration using my recorded Stream video below.  Sorry for the extra work but the district skipped a C day on the snow day. Also just keep in mind that we will not have any homework over the break.
                      
 
Spectrophotometry AP question 2 – 2003-1.pdf
View Download
Spectrophotometry AP question 2 – 2003 AP Key.pdf
View Download
 
Spectrophotometry AP question Tutorial Video:
 
Spectrophotometry Form:
 
You get one response today!

Spectrophotometry Intro Form

 
Recorded Redox Titration Lab :
 
End of Week 5!
 

 
 
 
 
 
 
 
 
 
 
 
 
 
NOT UPDATED BEYOND THIS POINT!