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Q1: Week 2  – 9/11 – 9/15

<- Week 1

If you have not already please join the REMIND for this class.

______________________________________________________                                                   Jump toMonday Homework             9/11 – Monday B Day – 2, 3b/4 Lab

Main focus –

a) To better understand the Standard Reduction Potential  Table and apply in to determine the Net E0cell – electromotor force (volts) for chemical reactions.

b) To review concepts of spontaneity, voltage, amperage through the Standard Reduction Table.

c) Review the concepts of the Daniell Cell (battery/voltaic cell) that includes spontaneity.

Summer Assignment Connections Key – 23-24 .pdf

Period 2, 3b:

1. Review / Complete Friday’s demo that (posted below) that reviews connects the concepts of a spontaneous/non-spontaneous redox reaction and the Standard Net Potential  ( E cell  ) values that are positive or negative volts.

Standard Net Potential (E cell) = voltages = potential difference = joules/C = Energy to move charge.
Voltages measure a pathway of electron flow (redox reactions) = Spontaneity = pathway!                                                                            A pathway allowed by nature is driven by an increase in Entropy. Entropy is the measure of the dispersion on energy from a concentrated source to a less concentrated source.

This is the reason why Heat flows to Cold! or Stored Energy is eventually released OR  Why a battery dies! Passive Transport!  Entropy gives us Free energy!!! Is there really renewable energy?

E0cell = NET VOLTAGE! (from redox reaction)

positive voltage = spontaneous = there IS a pathway that the universe allows = IT REACTS!

negative voltage = non spontaneous = there is a NO pathway that the universe allows = IT doesn’t
under the current set of conditions

Today’s Worksheets:

Redox 4 – Net potentials Demonstrations worksheet 1213.pdf

Redox 4 – Net potentials Demonstrations worksheet 1213 key p.pdf

Standard Reduction Potential Table.pdf

2. Daniell Cell Review: I reviewed the concepts of the an example of a voltaic cell. Video posted above in  Tuesday’s Homework reviews this lesson but today I will incorporate the concepts of spontaneity into it. It will include concepts from this weekends lecture.

I use a Danielle Cell demo to illustrate these concepts.

Period 4:

1. Complete Daniell Cell Review.

2. Lab 1 – Pre Lab –

LAB Activity 1 Making of batteries (voltaic or galvanic cell) – last 15 minute. In this Lab each person will make a pair of voltaic cells that if successfully created will power a 3 volt transistor radio.

a) Make one voltaic cell and identifies anode, cathode and tested voltage.
Identified the spontaneous process with positive volts
wrote half reactions, identified ox and red agents.

LAB 1 – Voltaic Cell.pdf

9/11 – Monday’s Homework: –

1. Please make 1 more submissions for a the Daniell Form (activity) posted belowPlease do so ONCE class is over,

2.  Read my *Connections NOTES –  POSTED IN This weeks notes (link: week 2 notes).

3. Watch the Voltaic Spontaneity lecture 2017 lecture below:

4.  Complete the Voltaic Spontaneity Form.  You have 3 total submissions for this form and it is on auto-reply so make sure you have the correct email entered.

________________________________________________

2 Daniell Cell lecture: Form:
This form is based in the lecture above. You have 2 submissions this weekend. It will be on auto-reply.

3Voltaic Spontaneity lecture:  This is for the homework form below..

4Voltaic Spontaneity Form:  This form is based in the lecture above.

End of Monday!

________________________________________
9/12 – Tuesday – A Day – 2/3a Lab, 4

Main focus–

a) To link the concepts of spontaneity to the voltaic cell.

b) To teach the concept of Le Chatelier’s Principle.

c) To begin Lab 1 – Construct a voltaic cell.

Period 2:

1. Review the Danielle Cell Lecture Form- with key
Skills:   Solubility, Spontaneity, Equilibrium,
How concentration of soluble ions in a voltaic cell affect its voltage.

2.  NO2 and N2O4  ampule demo with heat, viewing the ampule as equilibrium.

Manipulating the spontaneity with heat, in phase changes, adding salt to ice

3. LeChateliers Principle/ with worksheet

LeChateliers principle worksheet p.pdf

LeChateliers principle worksheet KEY 2012 p.pdf

4.  Re-vist the Classroom Danielle cell and predict voltage
by manipulating concentration of free ions

Period 3a/4:

1.  Lab 1 – voltaic cell – Pre – lab discussion

2. Construct the voltaic cell and test experimental voltage.

3. Label the components of the voltaic cell and run class radio by putting the 2 batteries built in series.

LAB Activity 1 Making of batteries (voltaic or galvanic cell) – last 15 minute. In this Lab each person will make a pair of voltaic cells that if successfully created will power a 3 volt transistor radio.

a) Make 2 voltaic cell and identifies anode, cathode and tested voltage.
Identified the spontaneous process with positive volts
wrote half reactions, identified ox and red agents.

LAB 1 – Voltaic Cell.pdf

LeChateliers Principle Notes:

 Notice that concentration of the NO2 is large initially and decreases as the reaction proceeds. Notice the initial concentration of N2O4 is zero (it has not been made yet) and increases as the reaction proceeds. Both NO2 and N2O4 eventually level out and at this point equilibrium has been reached! If the rate of 2NO2 combining to make N2O4 (forward reaction) is as fast as rate of N2O4 decomposing into 2NO2 (reverse reaction) then the concentration of both chemicals become CONSTANT at equilibrium.

 At point C, there 100% NO2  and 0% N2O4  thus there is no competing reaction because there is no NO2 to combine to make the N2O4.  The reverse reaction is at it maximum spontaneity and the forward reaction is at its minimum. There is a Shift in the reaction to move in the reverse. Over time its spontaneity will steadily decrease until it reaches the point of equilibrium and the “death of the reaction”. Notice that the equilibrium position is at the bottom!! This is where the death of the reaction or where there is ZERO Spontaneity or No more release of energy into the Universe.                                      ΔSuniverse = 0At point A we have 100% NO2 and 0% N2O4.  At this point there is tremendous pathway to go forward!  There is No competing backwards reaction!! The reverse reaction is impossible here.  It so spontaneous in the forward that the reverse is impossible!At point B, there is 60% NO2 and 40%  N2O4.Here we have a competing reaction reverse reaction thus the forward reactions is not as spontaneous and the reaction is getting closer to its death.  The reverse reaction is still not as spontaneous as the forward but it is closing in, thus the overall Net direction is still forward but this pathway is not nearly as great as point A.

Dissolving of a soluble salt :  Water can compete with the Coulombic attractions of ions in a salt.

LeChatelier’s Principle Lesson :  Period 4 only (up till 9:08)

*Period 4:  Please View the LeChateliers Principle Lesson (up till 9:08) posted above before you begin the LeChateliers Principle worksheet (#1) below. Everything else is the same for all classes.

1*. Complete selected questions from the Le Chateliers Principle worksheet (front side) given out in class
and review the key below. (Please complete questions  1, 4, 7)

( I will review Tomorrow for period 4)

LeChateliers principle worksheet p.pdf

LeChateliers principle worksheet KEY 2012 p.pdf

2. Please view my Demo video that was today’s demo. The video is posted below or use the link.

3.  Please complete Intro Voltaic Cells Worksheet 2 BUT PLEASE Complete QUESTION 2 ONLY!!

Intro Voltaic Cells worksheet 2 – skills.pdf
4.  Review question 2 (the one you just did) with the key below.

Intro Voltaic Cells worksheet 2 – skills Key p.pdf

5.  And/or you can follow along with me going over Question 2 with lecture below.
Intro Voltaic Cells worksheet 2 – skills.pdf  worksheet Lecture:

4: Today’s Demo

5: AP Chemistry Voltaic Cell Concepts Review worksheet 2 Video:

Click on the video below and it will  START AT 23:12 to view explanation to the solution to question 2.

Jump toWednesday Homework / top ______________________________________________                                                                                             9/13 – Wednesday B Day – 2, 3b/4 Lab

Main focus

a) To Complete the LeChateliers Concept with all stressors (concentration, temperature, pressure, volume, and the common ion effect).

b) To identify the voltage change in a voltaic cell due to Le Chatelier’s Principle with changes in the concentrations of ions in half cells, specifically when a precipitate is made.

c) To identify the precipitate in a net ion equation using the solubility rules or concepts.

Period 2,4:

1. Complete the LeChateliers principle concepts with all stressors and the worksheet
– Keep connecting to the U diagram- See LeChateliers Lesson below
m
LeChateliers principle worksheet KEY 2012 p.pdf

2Revisit the Classroom Daniell cell and predict voltage: See Diluting demo lecture below

a) Diluting the Reduction half cell ( Cu/Cu+2 ) or Blue One with water.

By adding water to the Cu+2 ion solution (molarity) decreased and thus the
Voltage Decreased!!!!

Explained in terms of LeChatelier’s Principle and Spontaneity!

Stress          Response

⬇︎ [Cu+2]          ⬆︎[Cu+2]

We added more water to dilute and lower the          The reaction responds to undo the stress by
concentration of copper ions.                                         moving toward equilibrium (in the reverse).

*We were lowering a reactant concentration by dilution and the reaction reacted by making more of the reactant to get to equilibrium.

Zn0  (s)   +    Cu+2  —–>   Zn+2    +     Cu0

Stress:                              decrease

Response:                       <—————– Shift =  voltage drop!
(lowers spontaneity of forward reaction)

Zn0  (s)   +    Cu+2  <—-   Zn+2    +     Cu0

⬆︎              ⬆︎             ⬇︎               ⬇︎

The reverse is favored more (than it was originally) which LOWERS the forwards reactions pathways or spontaneity, which results in lowering the voltage!

In terms of spontaneity:

b) Diluting the Oxidation half cell (Zn/Zn+2) or clear bleaker with water.

By adding water to the Zn+2 ion solution (molarity) decreased and thus the
Voltage Decreased!!!!   Explained in terms of LeChateliers Principle and Spontaneity!

Stress          Response

⬇︎[Zn+2]          ⬆︎[Zu+2]

We added more water to dilute and lower the          The reaction responds to undo the stress by
concentration of zinc ions.                                              moving toward equilibrium (in the reverse).

Zn0  (s)   +    Cu+2  —–>   Zn+2    +     Cu0

Stress:                                                       decreases
Response:                       Shift ———————> = Voltage increase!
(increases spontaneity of forward reaction)

We can decrease the concentration of dissolves ions (aq) another way besides adding water. We can precipitate out an ion if we add another salt that delivers an ion that will make an insoluble salt.
The homework for the weekend will have this concept.

Period 3a:

1.  Lab 1 continues

__________________________________________________                                                                                                                                                Lab 1 – The Gerber Voltaic Cell

Voltaic Cell Lab 1 – Making of batteries (voltaic or galvanic cell) – In this Lab each person will make a pair of voltaic cells that if successfully created will power a 3 volt transistor radio.

LAB 1 – Voltaic Cell.pdf

a) Made one voltaic cell and identifies anode, cathode and tested voltage.

Identified the spontaneous process with positive volts
wrote half reactions, identified ox and red agents.

b) Completed the diagram, conclusion questions, and reviewed errors for the writing of the
conclusion

&nbsp

Started answering questions 5, 6, 7, 8 from Lab:

question 6:  I should NOT have written that the Cu ions cannot pass through the dialysis tubing….

question 7:  What ions flowing can pass through the Dialysis Tubing (cellulose).

question 8:  What is fizzing – I will get to this the next lab period.

Error Analysis for the conclusion:

Chemical reactions that may have contributed:

Mg    +   HOH (water)   —–>  Mg+2  + 2OH   +   H2 (g)

Would these ions (Mg+2  + 2OH) form a precipitate with ions already present?  The color of the entire battery was bluish?                                                                             What does that say about movement of Cu+2 ions?

What factors were competing?  Based on the experimental voltage which factor dominated?

My video below illustrates the reaction occurring above (the fizzing or production of hydrogen gas).

Time Lapse – Lab 1

LeChateliers Lesson: Using the Ampules of NO2 and N2O4

Diluting the concentrations in the Danielle Cell Demo:

1. Complete side one of the LeChatelier’s Worksheet and review with the key.

LeChateliers principle worksheet p.pdf

LeChateliers principle worksheet KEY 2012 p.pdf

2. Complete Question 1 and 2 (AP Question 2002 and 2003)
Intro Voltaic Cells worksheet 1.pdf worksheet –
( They are Past AP problems ) –

Intro Voltaic Cells worksheet 1.pdf
Intro Voltaic Cells Worksheet 1 key pp.pdf
3.  Review with key posted above or the video posted below.

________________________________________________

2: Intro Voltaic cell worksheet 1 video:

End of Wednesday..

____________________________________________________________________                                                                                                            9/14 – Thursday – A Day – 2/3a Lab, 4

Main focus

a) To identify the precipitate in a net ion equation using the solubility rules or concepts.

b) To identify the voltage change in a voltaic cell due to Le Chatelier’s Principle with changes in the concentrations of ions in half cells, specifically when a precipitate is made or a common ion is added.

Period 2,4:
1.  Precipitation reaction demo – Double replacement reactions or precipitation reactions-
Net ion reaction written to eliminate spectators!

Net Ion Reaction Intro – Precipitation 1920.pdf

A) Wrote the precipitation reaction between lead (II) nitrate and potassium nitrate.
We used the following worksheet:

B) Particular Diagrams
C) Identified the precipitate using solubility rules (Table F)

2. Revisit the Danielle Cell and create a precipitate to change the voltage or spontaneity.

3. Review of the AP problems that was also assigned yesterday.

Intro Voltaic Cells Worksheet 1 key pp.pdf

In question 2 my key does not do a great job in answering some questions..

2a) overall reaction with the greatest voltage:

2Al (s)                 →     2Al+3 (aq)   +    3e- 6e-              +1.66 volts

3Cu+2    +   2e 6e-    →   3Cu (s)                                     +0.34 Volts                                                         _______________________________________________

2Al (s)   +   3Cu+2   →   2Al+3 (aq)   +    3Cu (s)            E0 cell = 2.00 volts

2d) Explain why each salt (ionic compound) is not appropriate:

NaOH –> Although OHis soluble and thus produces free ions that will “maintain electrical neutrality”  it will cause a precipitate with the Cu+2 ion in the reduction cell that will lower the reactants causing a shift to the left that would lower the voltage due to Le Chatelier’s Principle

CuS —> This salt is not soluble (large positive and large negative charges) thus their would be NO FREE IONS  “to maintain electrical neutrality” and thus this choice of salt in the salt bridge would cause the voltage to remain at zero!

NaNO3 —-> This salt is soluble and thus will produce free ions “to maintain electrical neutrality” and will facilitate a positive voltage.  This salt was weak coulombic attractions due to each of the ions having a low charge density.

_____________

D) Performed the demonstration.

Precipitation Demonstration:

Todays Notes: – Video of today’s demo posted below the notes

Revisit the Classroom Daniell cell and predict voltage by making the Zn+2 ions precipitate out with Na2CO3 being added to the Zn/Zn+2 half cell.

*By adding Na2CO3 I was really delivering CO3–2 ions to the oxidation half cell because Na2CO3 is soluble due to the group one ion (Na+) that has weak Coulombic attractions with the CO32 in the salt (ionic compound).

Na2CO3 (s)  →  2 Na(aq)   +  CO3-2 (aq)
carbonate ion
h
Then CO3-2 reacted with Zn+2 to form a precipitate, which takes  Zn+2 out of the solution.

Net ion reaction:    Zn+2 (aq)   +    CO3-2 (aq)    ZnCO3 (s) which is a precipitate = insoluble!

Why does the carbonate ion produce a precipitate with the zinc ion?

Coulombs Law!!!

Lowering the  Zn+2  will cause the overall reaction in the Daniell cell to “shift” Right or be move spontaneous in the forward direction increasing the voltage.

Zn0  (s)   +    Cu+2  —–>   Zn+2    +     Cu0
Stress:                                                             decreases
Response:                                     Shift —————–>

The forward reaction is now more favorable or spontaneous than the reverse thus
the voltage increases (becomes more positive)!

Daniell Cell – Le Chateliers Demo:  Today’s demo.

At 0:35 I add water to dilute the  Cu+2 into the reduction half cell.

At 1:33 of the video I add Na2CO3 (s) into the oxidation half cell.

At 0:35 I add water to dilute the  Cu+2

By adding water Cu+2 ion solution (molarity) decreased and thus the
Voltage Decreased!!!!   Explained in terms of LeChateliers Principle and Spontaneity!

Zn0  (s)   +    Cu+2  —–>   Zn+2    +     Cu0
Stress:                                      decreases
Response:                        <—————– Shift =  voltage drop!
(lowers spontaneity of forward reaction)            The reverse is now favored more than it was which LOWERS the forwards reactions
pathways or spontaneity, which results in lowering the voltage!

__________________________________________________                                                                                                                                                Lab 1 – The Gerber Voltaic Cell

Voltaic Cell Lab 1 – Making of batteries (voltaic or galvanic cell) – In this Lab each person will make a pair of voltaic cells that if successfully created will power a 3 volt transistor radio.

LAB 1 – Voltaic Cell.pdf

a) Made 2 voltaic cell and identifies anode, cathode and tested voltage.

Identified the spontaneous process with positive volts
wrote half reactions, identified ox and red agents.

b) Completed the diagram, conclusion questions, and reviewed errors for the writing of the
conclusion

c). re-measure voltage and calculate the average voltage (after a couple of days)

d)  Make observations (after a couple of days) of your voltaic cell.

&nbsp

Started answering questions 5, 6, 7, 8 from Lab:

question 6:  I should NOT have written that the Cu ions cannot pass through the dialysis tubing….

question 7:  What ions flowing can pass through the Dialysis Tubing (cellulose).

question 8:  What is fizzing – I will get to this the next lab period.

Error Analysis for the conclusion:

Chemical reactions that may have contributed:

Mg    +   HOH (water)   —–>  Mg+2  + 2OH   +   H2 (g)

Would these ions (Mg+2  + 2OH) form a precipitate with ions already present?  The color of the entire battery was bluish?                                                                             What does that say about movement of Cu+2 ions?

What factors were competing?  Based on the experimental voltage which factor dominated?

Time Lapse – Lab 1 – to help answer conclusion questions

1.  Please complete Intro Voltaic Cells Worksheet 2 BUT PLEASE Complete QUESTION 1.

Intro Voltaic Cells worksheet 2 – skills.pdf

2.  Review question 2 with the key below.

Intro Voltaic Cells worksheet 2 – skills Key p.pdf

3 And/or you can follow along with me going over Question 1 with lecture below.
Intro Voltaic Cells worksheet 2 – skills.pdf  worksheet Lecture: Play from the beginning.

4.  Please Study for a 15 minute –  1 page Quiz the voltaic Cell for Tomorrow 9/16
The question you just completed in Voltaic Cells Worksheet 2 is a great review.

Topics:

A) Labeling a complete voltaic cell:

1. Identify Anode and Cathode and their charges.
2. Determine the flow of electrons.
3. Label all ions in half cells (oxidation and reduction areas) AND in Salt Bridge.
4. Movement of ions in salt bridge.

B)  Write the Half reactions.
C)  Determine the overall Balanced Net ion reaction.
D)  Calculate the Net Potential (E0 cell) of the voltaic cell.

E) Predict how the voltaic cell’s voltage will change in response to stress.

Underlying Principles:
Coulombs Law, Le Chatelier’s Principle, Voltage vs Amperage, Spontaneity and Equilibrium,
Solubility and Precipitates, Reduction potentials.

3: AP Chemistry Voltaic Cell Concepts Review worksheet 2 Video: for Question 1!

Start from the beginning in the video.

___________________________________________________________________

9/15 – Friday – B Day – 2, 3b/4 Lab

Main focus

a) To identify the voltage change in a voltaic cell due to Le Chatelier’s Principle with changes in the concentrations of ions in half cells, specifically when a precipitate is made or a common ion is added.

b) To reinforce the concepts of the voltaic / galvanic cell by taking a 15 minute 1 page quiz.

Period 2,4:

1. Review of the Daniell cell with 3 stresses.

Intro Voltaic Cells worksheet 2 – skills Key p.pdf

A) Dilution of an ion:  Adding water that will lower the molarity = ratio of amount of ions to volume of water

B) Adding a salt that causes a precipitate that lowers the molarity of an ion.– question 1: Intro Voltaic Cells
worksheet 2 – skills
C)  Adding a salt that provides a common ion.  – question 2:    Intro Voltaic Cells
worksheet 2 – skills

* B) and C) only have an effect on changing voltage or spontaneity of the forward direction of the redox reaction if the ion that is effected is in the overall reaction! For the Daniell cell is must be:

Zn0  (s)   +    Cu+2  —–>   Zn+2    +     Cu0

So only the Cu+2  or  Zn+2   are the ions and their concentration changes that can create a stress that will cause the reaction to shift (become more favorable).  If the ion is NOT COMMON to the overall reaction of the redox reaction (in the voltaic cell) then there will no effect on spontaneity or voltage.

What is also important is that the solid electrodes cannot be diluted or increased as they do not make solutions so we are only left with the (aq) ions that can be altered to CREATE A STRESS that will change the spontaneity of voltage of a voltaic or galvanic cell.

Positive volts = Favorable Pathway = Spontaneous = entropy of universe (∆S) increasing (∆S) increasing= energy dispersed = obtain Free Energy (∆G) to do work (power our phones!)

2. Complete the discussion of Lab 1.  – View Time Lapse of Gerber Cell

– Production of precipitate

– limitations/errors – production of hydrogen gas

3. Complete a 15 minute quiz.

Period 3b:

1. Lab 1 Completion.

__________________________________________________                                                                                                                                                Lab 1 – The Gerber Voltaic Cell

Voltaic Cell Lab 1 – Making of batteries (voltaic or galvanic cell) – In this Lab each person will make a pair of voltaic cells that if successfully created will power a 3 volt transistor radio.

LAB 1 – Voltaic Cell.pdf

a) Made 2 voltaic cell and identifies anode, cathode and tested voltage.

Identified the spontaneous process with positive volts
wrote half reactions, identified ox and red agents.

b) Completed the diagram, conclusion questions, and reviewed errors for the writing of the
conclusion

c). re-measure voltage and calculate the average voltage (after a couple of days)

d)  Make observations (after a couple of days) of your voltaic cell.

&nbsp

Started answering questions 5, 6, 7, 8 from Lab:

question 6:  I should NOT have written that the Cu ions cannot pass through the dialysis tubing….

question 7:  What ions flowing can pass through the Dialysis Tubing (cellulose).

question 8:  What is fizzing – I will get to this the next lab period.

Error Analysis for the conclusion:

Chemical reactions that may have contributed:

Mg    +   HOH (water)   —–>  Mg+2  + 2OH   +   H2 (g)

Would these ions (Mg+2  + 2OH) form a precipitate with ions already present?  The color of the entire battery was bluish?                                                                             What does that say about movement of Cu+2 ions?

What factors were competing?  Based on the experimental voltage which factor dominated?

Time Lapse – Lab 1 – to help answer conclusion questions

Lab 1 – Put all the Voltaic cells in series to run large radio.

1. Please review the graded quiz that will be emailed back to you sometime today.  A blank copy and the key will be posted below as well as a complete review video which is posted above.. You have another quiz Wednseday which will be the best out of 2!

Today’s Quiz Key will be posted here after period 4:

Voltaic Cell quiz 1.pdf

2.  Complete both sides of the worksheet below and review with the key. Skip question 6 iii in question 6.

Recent Voltaic Cell AP Test Questions .pdf

Recent Voltaic Cell AP Test Questions key p.pdf

3. Complete Lab  1, including Conclusion  – It is due Tuesday, 9/18
5

Conclusion Writing:

1.  What did find or measure Quantitatively?  What are the important values of your data?  This is normally posted in your results section of a formal writeup. How accurate are you (how close are you to a known standard, E0 cell )?

2.  Make the leap!  = connect your quantitative value and comparison with the known standard in terms of atom/ions or particle to explain a possibly reason for the outcome.

3. Error discussion.
Every laboratory is limited in errors in measurement and human errors. Do not write about these!! Please describe in detail every major limitation of this laboratory and why you believe it may have lead to your outcome.
IN this Lab the error discussion will result from things that are NOT FROM YOUR LEAP!  Do nor just list errors. I want an explanation how these errors could of resulted in YOUR OUTCOME.
Lab 1 Conclusion review:

1. Please tell me what you measured (voltage) and calculated (percent error). Do not mince words.  Get to the point. This is like our results section last year in our formal labs.

2/3:  Explain your errors (why your percent error was so low or negative).  You will combine the leap with the error analysis here.  The leap last year was always about an organism and the leap this year is always about atoms or ions.  So what did the atoms or ions do that may have contributed to the large negative error?  There is one error that is the largest and I like to think of it as a love triangle between Mg, Cu+2 , and H2O.

This cell was left over night.  Notice the Mg electrode is smaller and the cloudy mixture.  Were there precipitates?
How did this contribute to the error?  Or was this a competing error?  Notice some of the precipitates seem to be bluish green, which is an indication that Copper precipitates were also made.

Review of the Voltaic cell quiz given Today: I will open this video after both classes finish the quiz today.